aspemo

AOP and Spring

2011-12-14T00:59:00.001-08:00

Logging aspects and Spring.

Add this to your applicationContext.xml file.

 
       
   
     
   
       
           service,logic,integration
       
       
           
               loggingAdvice

This will cause the three beans, service, logic and integration to be logged.

This will cause the "bean" loggingAdvice to be exposed in the JMX console with the name TestLogging

This will expose the property enabled to the JMX console, set that to true and the aop starts to log.

Below is the complete Logging advice class.

package com.aja;

import org.springframework.aop.AfterReturningAdvice;
import org.springframework.aop.MethodBeforeAdvice;
import org.springframework.aop.ThrowsAdvice;

import com.ericsson.sdp.media.eup.charging.error.ErrorHandler;

import java.lang.reflect.Method;


/**
* Logging interceptor.
*/
public class LoggingAdvice implements MethodBeforeAdvice, AfterReturningAdvice,
   ThrowsAdvice {
   private boolean enabled = true;
  
 
  
   /**
    * Transcodeeates a new instance of LoggingAdvice.
    */
   public LoggingAdvice() {
   }

   /* (non-Javadoc)
    * @see org.springframework.aop.MethodBeforeAdvice#before(java.lang.reflect.Method, java.lang.Object[], java.lang.Object)
    */
   public void before(Method method, Object[] args, Object target)
       throws Throwable {
       if (!enabled) {
           return;
       }

       StringBuffer builder = new StringBuffer();
       builder.append("enter ").append(method.getName()).append("(");

       for (int i = 0; args == null?false:(i < args.length); i++) {
           builder.append(args[i]);

           if (i < (args.length - 1)) {
               builder.append(", ");
           }
       }

       builder.append(")");
     
       ErrorHandler.handleDebug(builder.toString());
  
   }

   /* (non-Javadoc)
    * @see org.springframework.aop.AfterReturningAdvice#afterReturning(java.lang.Object, java.lang.reflect.Method, java.lang.Object[], java.lang.Object)
    */
   public void afterReturning(Object returnValue, Method method,
       Object[] args, Object target) throws Throwable {
       if (!enabled) {
           return;
       }

       ErrorHandler.handleDebug(RETURN + method.getName());
   }

   /**
    * @param method
    * @param args
    * @param target
    * @param exc
    */
   public void afterThrowing(Method method, Object[] args, Object target,
       Throwable exc) {
       if (!enabled) {
           return;
       }
      
       ErrorHandler.handleDebug("return " + method.getName() + exc.getMessage());
     
   }

   /**
    * @return the enabled
    */
   public boolean isEnabled() {
       return enabled;
   }

   /**
    * @param enabled the enabled to set
    */
   public void setEnabled(boolean enabled) {
       this.enabled = enabled;
   }
}

Struts2 and portlet

2011-12-14T00:58:00.002-08:00

This is a short how to get a Struts2 application up and running in JBoss portal framework.

We will use the following tools one at a time in this tutorial.

Tools:

JBoss 4.0.5 with the portal extension.

Maven 2.0.4

Struts 2.0.6

Ubuntu Edgy Eft

Java 5.

Note this. There is a fundamental difference between Struts1 and struts2. The whole concept is changed and Struts has moved
away from the straight flow based approach to a more object oriented way with dependency injection. There are a multitude of sites about this, but the best staring point is probably the Struts homepage.

So before starting. The disclaimer is that in a serious production environment, this application will not be enough. This is just a test for the home cooker.
Step 1.

Install JBoss 4.0.5 and pick the one with version number 4.0.5 and choose Run Installer. That's right, make sure you choose "Run Installer".

Pick installation language.
This should be standard stuff. You go next all the time and accept the license agreement (well, only if you accept it of course). pick installation directory.
For the sake of argument I choose /jbossportlet. Pick your choice and then press next.
let the installation program create the directory. Press ok.
You have to choose protal here.

In your jbossportal/bin directory there are two files of interest.
run.sh and run.conf make a copy of each and name them debug.sh and debug.conf. Edit debug.sh and find the one and only occurence of the word run.conf in the file. Change this to debug.conf.
Now change the debug.sh file and remove the bracket# in fron ot the line where it says something like this,
#JAVA_OPTS="$JAVA_OPTS -Xdebug -Xrunjdwp:transport=dt_socket,address=8787,server=y,suspend=y"
When youe are done the ine should be like this
JAVA_OPTS="$JAVA_OPTS -Xdebug -Xrunjdwp:transport=dt_socket,address=8787,server=y,suspend=y"
OK. Test JBoss now go to the installation directory/bin and type ./run.sh this should fire up your JBoss app server.

To see if it works type http://localhost:8080/portal and the JBoss portal page should appear. Do not panic if it takes a while. If you do not see this page
without errors do not bother to proceed, something is major wrong at your place right now.

Maven
Install Maven go to Mavens home page.
I used version 2.0.4. Not that it really matters, but version numbers are important in ceratin circles.
There is a web.xml file in the WEB-INF directory, if you don't do this Maven doesn't build your web app.
Add one pom.xml to the main MyPortlet directory and add one pom.xml to the MyPortlet.war directory.
The content is as follows.
The top pom.xml shall look like this. This is the pom in the MyPortlet directory.

4.0.0
Maven Default Project
com.aja.myportlet
MyPortlet
1.0
pom

MyPortlet.war

org.apache.maven.plugins
maven-compiler-plugin

1.5
1.5

The pom.xml in the MyPortlet.war directory shall look like this.

4.0.0

com.aja.myportlet
MyPortlet
1.0

MyPortlet.war
war

junit
junit
4.1
test

log4j
log4j
provided
1.2.13

javax.servlet
servlet-api
2.5
provided

opensymphony
xwork
2.0.1

commons-logging
commons-logging
1.0.4

commons-attributes
commons-attributes-api
2.1

commons-collections
commons-collections
3.2

freemarker
freemarker
2.3.4

org.apache.struts
struts2-core
2.0.6

asm
asm
1.5.3

Go to the MyPortlet.war directory and exceute this command.
mvn clean install
Eclipse.
I assume you know Eclipse. Otherwise you are in for a long journey. Now make the eclipse project file in maven by
executing this mvn eclipse:eclipse.
Import the project. You must define your Maven repository in the Eclipse class-path setting. The variable is called M2_REPO and you must point to your Maven repository. If you are unsure check out the Maven documentation.
In windows most of the time you'll find the REPO in the Documents folder.
Coding
When we are done the following files will exist in our project.
In the WEB-INF directory
jboss-app.xml
jboss-portlet.xml
MyPortlet-object.xml
portlet.xml
web.xml
I also felt a need to add this tld as well. It can be found in the Struts2.0.6.core jar in the /META-INF directory.
I don't think you need them but I have to verify that.
struts-tags.tld
In the src/main/resources directory
struts.xml
In the WEB-INF/pages/view (Yes you must create that directory)
helloForm.jsp
helloWorld.jsp
And we'll do one Java class and put it in
src/main/java/com/aja/mp/action/HelloWorldAction.java
The content of all files (except tlds) will be shonw below. If you add this content your application will work.
struts.xml

/WEB-INF/pages/view/helloForm.jsp

/WEB-INF/pages/view/helloForm.jsp

/WEB-INF/pages/view/helloWorld.jsp

jboss-app.xml

MyPortlet

jboss-portlet.xml

<portlet-app> <portlet> <portlet-name>MyPortlet</portlet-name> <security> </security> </portlet> </portlet-app> 

MyPortlet-object.xml

<?xml version="1.0" encoding="UTF-8"?> <deployments> <deployment> <if-exists>overwrite</if-exists> <parent-ref>default</parent-ref> <properties /> <page> <page-name>MyPortlet Tutorial</page-name> <properties /> <window> <window-name>MyPortletWindow</window-name> <instance-ref>MyPortletInstance</instance-ref> <region>center</region> <height>0</height> </window> </page> </deployment> <deployment> <if-exists>overwrite</if-exists> <instance> <instance-name>MyPortletInstance</instance-name> <component-ref>MyPortlet.MyPortlet</component-ref> </instance> </deployment> </deployments> 
portlet.xml

My very first struts Portlet
MyPortlet
My first WebWork Portlet

org.apache.struts2.portlet.dispatcher.Jsr168Dispatcher

viewNamespace
/view

defaultViewAction
index

0

text/html

en

My very own WebWork Portlet
WWPortlet
struts,portlet

web.xml

struts

org.apache.struts2.dispatcher.FilterDispatcher

struts
/*

org.apache.struts2.portlet.context.ServletContextHolderListener

preparator

org.apache.struts2.portlet.context.PreparatorServlet

/struts-tags
/WEB-INF/struts-tags.tld

helloForm.jsp

<%@ taglib uri="/struts-tags" prefix="ww" %>

Hi there! Please enter your name

helloWorld.jsp

<%@ taglib uri="/struts-tags" prefix="ww" %>

Hello

">Back to form

HelloWorldAction.java

package com.aja.mp.action;

import java.util.Collection;

import com.opensymphony.xwork2.ActionSupport;

public class HelloWorldAction extends ActionSupport {
/**
*
*/
private static final long serialVersionUID = 2452536171755317259L;
private String firstName;
private String lastName;
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
@Override
public String execute() throws Exception {
// TODO Auto-generated method stub
return super.execute();
}
@Override
public Collection getActionMessages() {
// TODO Auto-generated method stub
return super.getActionMessages();
}
}

We are done, build and deploy the application.
mvn clean install
Rename and copy war to /jbossportal/server/default/deploy/MyPortlet.war
You will most probably get two errors at start up time, you can ignore those if it one complaining about a dev property and another complaining about i18.

Struts

2011-12-14T00:58:00.001-08:00

This is a short how to get a Struts application up and running.
The following run time configuration was used
jdk1.5.0_09
Jboss4.0.5
Ubuntu Edgy Eft
The following development environment was used
Eclipse3.2.2
Web Tools plugin 1.5.1
Struts version used is 1.3.8.
If you need a more thorough explanation on the MVC2 pattern browse the net.
You need some things to get it to work. First off the struts-config.xml file.
This file should be in the WEB-INF directory. Remember, WEB-INF makes the file inaccessible to the outside world.

Well, well what does all that mean.
First off a form-bean. And now, what does a form bean do? It basically means that
if you post data Struts make sure that your parameters are sent to the server and handled there.
For instance if you post a user name that name will be sent to the server, and the instance of the form class will use getters/setters and use that.
All form beans must extend the org.apache.struts.action.ActionForm; Please override the validate method since this makes it possible for you
to handle erroneous data in a good way. I have implemented the reset method as well.
my form bean
public class StartForm extends ActionForm {

/**
*
*/
private static final long serialVersionUID = -3219629289363196387L;

private String name;

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

/**
* Reset all properties to their default values.
*
* @param mapping The mapping used to select this instance
* @param request The servlet request we are processing
*/
public void reset(ActionMapping mapping, HttpServletRequest request) {
this.name=null;
}

/**
* Reset all properties to their default values.
*
* @param mapping The mapping used to select this instance
* @param request The servlet request we are processing
* @return errors
*/
public ActionErrors validate(
ActionMapping mapping, HttpServletRequest request ) {
ActionErrors errors = new ActionErrors();

if( getName() == null || getName().length() < 1 ) {
errors.add("name",new ActionMessage("error.name.required"));
}

return errors;
}
Ok, now we are done with the Form. This is the Model aprt of the pattern. The model can be seen as a stupid data carrier.
We'll take the action now.

public class StartAction extends Action {
package com.aja.lib.action;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionErrors;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
@Override
public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception {

ActionErrors errors = form.validate(mapping, request);

if (errors.size() > 0){
return mapping.findForward("fail");
}

return mapping.findForward("success");
}

}
As you can see, extend the org.apache.struts.action.Action class and override the execute method. You have two different outcomes. In case of a success go to
"success" and in case of error go to "fail". These two paths must be mapped in the struts-config.xml file. Remember this code.

The action in our case is where you usually put your calls to the tiers behind the presentation tier, i.e business tier. This is the C in MVC, the control part, the traffic handler.
What about the View? Well, look above in the code "success.jsp" and fail.jsp that's our views. They must exist.
First off the start point that we defined in the struts-config.xml, start.jap
<%@ page language="java" pageEncoding="ISO-8859-1"%>

<%@ taglib uri="http://jakarta.apache.org/struts/tags-bean" prefix="bean"%>
<%@ taglib uri="http://jakarta.apache.org/struts/tags-html" prefix="html"%>
<%@ taglib uri="http://jakarta.apache.org/struts/tags-logic" prefix="logic" %>

Wddfsd

Please Enter the Following Details
Name
Save	Cancel

Now here we see some magic. Note the html:text property="name", this will be mapped towards our form beans setName method.
I made it simple here, success just forwards to a stupid empty page, and fail back to start.jsp. below is my success.jsp
<%@ page language="java" pageEncoding="ISO-8859-1"%>
<%@ taglib uri="http://jakarta.apache.org/struts/tags-html" prefix="html" %>

Sucess

Deploy it and write http://locahost:8080/LibWeb/start.jsp. Good luck now.
One final word, if you develop something for real, you will most likely for instance not have a .jsp instead you can add in the configuration a lot of default handling stuff.

Create a simple JavaEE application with XFire

2011-12-14T00:57:00.002-08:00

This is simple step by step tutorial on how to build an application that will display content on web pages. Everything will be done in a pedagogic simple way.The nuild is done with the Apache Maven framework instead of ant.

Below is a small list of tools used. All fancy words or strange settings will be omitted. In 90% of the applications you build you can use the default settings and they will work.

This tutorial contains these parts;
Part 1 - Create a stand alone application accessing a database with Hibernate.
Part 2 - Add web pages and access the database by calling methods on the application built in part 1. Deploy it on a server.
Part 3 - Change the application to use a datasource instead of a driver manager.
Part 4 - Add Ajax to interact with server.

Part 5 - Add ejb to use as a session facade to the methods created in part 1.

I used hiberate as the orm mapping system. Nobody uses raw sql anymore, at least not professionally. Many use the new JPA standard that was introduced together with EJB3.0 (which indirectly use TopLink or Hibernate). Most of the time I use JPA as well and use the underlying implementation on the application server. For JBoss default is Hibernate and for Sun it is Oracles Toplink. In this tutorial we use the "old fashioned" Hibernate directly.

Tools used

Eclipse 3.3.1.1 - to edit files
MySql 5.0.5 to store content
Maven 2.0.9 - to build project
Part 2 Apache 2.0 - to run web application
Part 2 Tomcat 5.5.17 - to execute java code
Part 5 JBoss 5.0.0 - to run Java EE app

Tutorial One, create a web service project with XFire

This tutorial will show how you can create an application with XFire from Codehouse. It will not access the database and it will have hardwired properties.Note that today most people use the JAX-WS API directly in the Java EE and do not use aweb service framework at all.

Step 1. Create project
People do this differently, but this is how I do it. Create three folders, call the first one book, add two folders within this one, call them bookjar and bookwar. The war project is not needed for the moment.
I always add a suffix to my projects to indicate which type of packaging to use, jar, war, ejb or ear. In each folder add a file called pom.xml.

Step 2. Create pom files in each folder

In the top folder book add this pom file whichjust define some aspects of the project. Note that there is probably as many ways as there are developers out there when it comes to writing pom files.

As you can see I have already added the MySql to the pom because I know I will need it later.

In the bookjar folder add this pom file.
In the bookwar folder add this pom file.

Step 3. Create files needed for the build

Now you are almost done. First, before you can build the application you must have directory structure.

The jar project shall have this structure;

src/main/java
src/main/resources
src/test/java
src/test/resources

The war project must have this structure;

src/main/java
src/main/resources
src/test/java
src/test/resources
src/main/webapp/WEB-INF
src/main/webapp/META-INF

It is very important to understand that Maven will not be able to build the application without a web.xml file in the WEB-INF directory. This is just a simple plain one.

If maven do not find the dependency jars you must install them into your repository. Note. Sometimes it can be a bit confusing or some overhead to get Maven to work. For instance you might need jar files which do not exist in the maven repository. These will have to be installed manually. Do not give up, it is worth the extra job. After that you will notice how much easier it is to run the build process.

What we need to do now is create the "stuff" we will work with. I will not go into the details, instead see the import statement in the file header, these will indicate where these files shall reside. I.e. in which java packages they are expected to be found.

Step 4. Create java files needed in the application

Write eclipse:eclipse and import the projects into Eclipse.

We will create 3 java files.

se.aja.xfire.Book.java (java class)
se.aja.xfire.BookService.java (java class)
se.aja.xfire.BookServiceImpl.java (java interface)

One is our domain object (book), this is what the site is about, books. Since it is so small we use the same object from the database out to our jsp pages.This is one strategy, the other is to convert the objects before displaying them.Two is the service. Put all these objects in the jar project. Thus when you are done in the jar project you shall have these files;

src/main/java/se/aja/xfire/Book.java
src/main/java/se/aja/xfire/BookService.java
src/main/java/se/aja/xfire/BookServiceImpl.java

Step 5. Create XFire service file and modify web.xml

You will need to add the XFire services.xml file to the META-INF directory. When you are done in the war project it shall look like this.

src/main/webapp/WEB-INF/web.xml (standard web app file)
src/main/webapp/META-INF/services.xml (XFire configuration file)

Services is the main xfire configuration file. In here you tell the system which service is to be published. In our case the service is called BookService. Quite fitting when it comes to my big interest, books.

Step 6. The service.xml file content

The file might look like this.

BookService
http://xfire.codehaus.org/BookService
se.aja.xfire.BookService
se.aja.xfire.BookServiceImpl

The service class indicates which service to publish and the implementation class is the concrete class implementing the interface.

One strange thing occurd to me, and is is also written about it on codehaus. I got a file not found error. I followed this instruction and got it to work.
Try "WEB-INF/classes/META-INF/xfire/services.xml" if the system cannot find the file. I.e. add a directory META-INF into the classes directory and add the services.xml there.

Step 7. The domain object (Book.java)

Let's assume the book class just contain an author and a title. It might look like this then. Pls. ignore the obious bad programming regarding null pointers and whatsoever. This is a pojo.

package se.aja.xfire.Book;

import java.io.Serializable;

public class Book implements Serializable{

private String author;
private String title;

public String getAuthor() {
return this.author;
}

public void setAuthor(String author) {
this.author = auhtor;
}

public String getTitle() {
return this.title;
}

public void setTitle(String title) {
this.title = title;
}
}

Step 8. The service definition (BookService.java)

BookService.java - Our service interface, remember S(ervice)OA.
The service just publishes some methods.

public interface BookService extends Serializable {
public List getBooks();
}

Step 9. The service implementation (BookServiceImpl.java)

BookServiceImpl.java - Our class implementing the interface.

public class BookServiceImpl implements BookService {
private List books;

public BookServiceImpl(){
books = new Arrayist();
Boook b1 = new Book();
b1.setAuthor("Jonas");
b1.setTitle("Blaha");

Boook b2 = new Book();
b2.setAuthor("Aspemo");
b2.setTitle("Blaha again");

books.add(b1);
books.add(b2);
}

public List getBooks(){
return books;
}
}

Step 10. Configure the web.xml file to handle XFire

You have to add the xfire servlet to your web.xml file. Add the following between the webapp tag in that file.

XFireServlet
XFire Servlet

org.codehaus.xfire.transport.http.XFireConfigurableServlet

XFireServlet
</servlet/XFireServlet/*

XFireServlet
/services/*

Your web.xml file should look like this now.

Step 11. Fix context root for Sun Application Server

Your application will default to the name of the war, i.e. war-1.0.0. If you want to define a context name do like this.

Add sun-web.xml file to the WEB-INF directory and add this code there

/book

if running on a Sun Application Server or add a jboss-web.xml into the

Step 12. Fix context root for JBoss Application Server

Your application will default to the name of the war, i.e. war-1.0.0. If you want to define a context name do like this.

Add jboss-web.xml file to the WEB-INF directory and add this code there;

book

Step 13. Deploy the application
Run the web application by deploying it to your favourite servlet container.

Type,
http://localhost:8080/book/services/BookService?wsdl and you see your exposed web service.

That is what the default context name should be.If you are unsure and wants to define context.

Your first xfire app is working. Test the methods with SOAP UI. Take a break. Drink a coke or a coffee.

Step 14. What's left

Well most obviously we lack the functionality to access things in the database. The Book file is hardwired with some data. That

EJBPoolSize

2011-12-14T00:57:00.001-08:00

I had a discussion on the EJB Pool size on a Sun Application Server. The documentation is a bit vague (to say at least) on how it really works.

First the definition. The EJB pool size is a way for the EJB container to create (pool) stateless session beans to serve client requests. The max pool size do sound a lot like a theoretical limit on how many request that can be served simultaneously. But that is not so actually. This is just a number on how many EJBs that are pooled over a long run. If more requests comes in, more beans are created. So, even if you have 200 as a max size, 500 clients can be served at the same time. Interesting?

The annotation @PostConstruct will show you the meaning of the pool. If you have a pool size of 5, you send in 10 simultaneous 10 calls to the @PostConstruct will be shown, BUT, the next request coming after say 1 second will not call @PostConstruct since those pools are pooled and the @PostConstruct are called before the bean is created and used by a client. This is the implications of the pool size.

Note also that the pool handling is application vendor specific. This is tried and verified on a Sun Application Server version 9.1.

I will let you create the project by yourself since that is no issue. In the ejb I added these methods.

@PostConstruct
public void createIdentity(){
System.out.println(" PostConstruct ");
}

This will print out the row PostConstruct every time an ejb is created. And yes, I would naturally never use Sys out in a real enterprise project.

public String getTimerName(){
System.out.println("Get Timer Name");
try
{
Thread.sleep(10000);
} catch (Exception e)
{
e.printStackTrace();
}
return "Jonas A";
}

This will sleep the thread for 10 seconds.

Next I changed the pool size setting in the App server to be max 5.

Then I made a servlet with this method in;

long start = System.currentTimeMillis();
InitialContext ic = new InitialContext();
BookService bk = (BookService) ic.lookup("Jonas");
bk.getTimerName();

long end = System.currentTimeMillis();

diff = end - start;

No matter how many simultaneous calls you make this method only takes 10 seconds and the trace shows that the app server creates as many PostConstruct statements as simultaneos calls, no matter how many they are.

After a time you might notice new PostConstruct statements even if you only make one call. This is because pooled instances are discarded after a while. A new flag STEADY_STATE can configure this behaviour as well.

Aspects and Maven

2011-12-14T00:56:00.003-08:00

Many times you might want to implement restrictions on what developers are allowed to do. For instance, you might want to prohibit the usage of System.out in Java EE applications.

One way is to add triggers in your version control system. Another way is to add aspects. This short how to shows what you need to do the get aspects working.

Step 1

Create a new project, and add it to the super pom. Thus if you want to build a book application your super pom might look like this;

book-jar

book-war

Now add the new project which will contain your aspects, call it for instance aspect (or whatever).

your super pom shall look like this now;

book-jar

book-war

aspect

Create the aspect project with normal directory structure.

src/main/java/org/aja/aspect/

In the aspect directory we shall add our restriction;

Let's call it DoNotPrint.aj

File DoNotPrint.aj

public aspect DoNotPrint {

private pointcut withinBook() : within(org.aja..*);

declare error:
withinBook() &&
get(* System.out):
"Accessing System.out is not allowed.";

declare error:
withinBook() &&
get(* System.err):
"Accessing System.err is not allowed.";

declare error:
withinBook() &&
call(* java.lang.Throwable.printStackTrace()):
"Calling Throwable.printStackTrace() is not allowed.";
}

The file says that it shall weave all files in the package structur org.aja and send an error when it finds a System.out. Change decalre error to declare warning if you think that is sufficient.

Now manipulate the pom.xml in the aspect project. The super pom is finished.

Step 1, add a dependency to the proper aspect jar and all projects we shall weave

aspectj
aspectjrt
1.5.2a
provided

org.aja
book-jar
1.0.0
provided

org.aja
book-war
1.0.0
provided

So, we added both a dependency to the aspect jar which is needed for all operations and the two projects we want to verify, or weave.

Add this to the build tag.

org.codehaus.mojo
aspectj-maven-plugin

compile

1.5
1.5

org.aja
book-jar

org.aja
book-jar

That's it. Everytime you stand in the top of the project and build the book-jar, book-war and aspect it will browse through all your classes and the build will fail with an error message if it finds any instances of System.out in the code.

Classpath

2011-12-14T00:56:00.001-08:00

If you don't work in an IDE, such as Eclipse or Netbeans, where do you put your java files?

The answer is in your /classes directory.

Step 1

Let's assume you create a class called DumbNumber which prints a digit.

public class DumbNumber {

public static void main(String...args) {

System.out.println("Dumb number is 7");

}

JPA

2011-12-14T00:55:00.004-08:00

This is a a step by step instruction on how to create an ejb project and call it from a stand alone java class and from a web page. Basically what the application will do is connect Authors and Books and display it in a GUI.

The work order is.

One ejb (Steteless session bean)

Two entity classes
One pom.xml file per project (all in all 2 pom files)
Everything will be built with maven

Step 1 -Create maven project structure

Top directory is called book and beneath it we create two projects, bookejb and bookwar

Step 2 - Add two pom files, first the top pom.

4.0.0

Parent
org.aja.book
parent
1.0.0

pom

ejb

org.apache.maven.plugins
maven-compiler-plugin
2.0.2

1.5
1.5

Step 3 - Add pom file in ejb project

org.aja.book
parent
1.0.0

org.aja.book
4.0.0
ejb
1.0.0
ejb
Aja EJB

java
java-ee
5.0
provided

Step 4 - Now we must create an ejb-jar.xml file in the directory structur, otherwise maven will not build.

In the ejb project create this. src/main/resources/META-INF/ejb-jar.xml

This file must contain this;

aja-book-ejb

Step 5 - build

execute mvn clean install

Create data source

First step is to add the actual database handling. Since we are using ejbs we must use an EJB container to run it, in our
case the Sun Server. Let's add a data connection.

How to do it can be found elsewhere but in short, in the App Server, go to

Resources->JDBC->Connection Pools;

Choose DataSource class name.

If you work with say mysql or toplink, you must put the jar file in the App Servers lib directory. I doesn't matter in
which lib (the AppServers top lib directory, or the domain lib directory) . As you probably understand, in the top lib all
applications can share it, in the domain only those classes find it.

Make sure the connection type is

javax.sql.ConnectionPoolDataSource.
Make sure to ping the database when you are done.

Ok, add
Resources->JDBC->JDBC Resources

Add a jndi name to your connection pool. I will call my pool

jdbc/BookPool

Now, add a persistence.xml, in the src/main/resources/ folder. My file looks like this;

jdbc/__default

Bascially the file contain the name of the Pool which
we deined in the App Server. If everything is ok, they will connect
with each other and live happily ever after. At the moment we leave all
transaction handling and stuff like that to
the wise care of the application server and all default vales. These
values are often sensible and in 99% of the cases you can let them stay
as they are.

Create java classes

The business objects contain all getter/setters we need and we will create it in org.book.business. We build a really small application so we will use the same objects within the whole application, from the database to the exposed services. We are now only working in the ejb project.

Step 6- Add Author entity

Add the Author.

package org.aja.book.business;

import java.io.Serializable;
import java.util.Collection;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;
import javax.persistence.Table;

import static javax.persistence.CascadeType.ALL;

@Entity
@NamedQueries( {
@NamedQuery(name = "getAllBooksByAuthor", query = "SELECT A FROM Author A WHERE A.firstName = :firstName AND A.lastName = :lastName")})

@Table(name = "AUTHOR")
public class Author implements Serializable {

/**
*
*/
private static final long serialVersionUID = 5172793849216643729L;

protected Collection books;

@OneToMany(cascade = ALL, mappedBy = "author")
public Collection getBooks() {
return books;
}

public void setBooks(Collection books) {
this.books = books;
}

private String firstName;

private String lastName;

private String id;

@Id
public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

public String getFirstName() {
return firstName;
}

public void setFirstName(String firstName) {
this.firstName = firstName;
}

public String getLastName() {
return lastName;
}

public void setLastName(String lastName) {
this.lastName = lastName;
}

}

Step 7 - Add the book entity.

package org.aja.book.business;
import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;

@Entity
@NamedQueries( {
@NamedQuery(name = "getAllBooks", query = "SELECT B FROM Book B")})
@Table(name = "BOOK")
public class Book implements Serializable {

/**
*
*/
private static final long serialVersionUID = -5901348294266358004L;

private Author author;

private String title;

private int pages;

private String id;

@Id
public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}

public int getPages() {
return pages;
}

public void setPages(int pages) {
this.pages = pages;
}

@ManyToOne
public Author getAuthor() {
return author;
}

public void setAuthor(Author author) {
this.author = author;
}

}

Step 8 - Add remote interface

package org.aja.book.service;

import javax.ejb.Remote;

@Remote
public interface BookServiceRemote extends BookService {

}

Step 9 - Add local interface

package org.aja.book.service;

import javax.ejb.Local;
@Local
public interface BookServiceLocal extends BookService {

}

Step 10 - Add service interface

package org.aja.book.service;

import java.util.List;

import org.aja.book.business.Author;
import org.aja.book.business.Book;

public interface BookService {

public void addBook(Book book);

public List getAllBooksByAuthor(Author author);

public List getAllBooks();
}

Step 11 - Add concrete class implementing the service interface

package org.aja.book.service.impl;

import java.util.List;

import javax.ejb.Local;
import javax.ejb.Remote;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;

import org.aja.book.business.Author;
import org.aja.book.business.Book;
import org.aja.book.service.BookService;
import org.aja.book.service.BookServiceLocal;
import org.aja.book.service.BookServiceRemote;

@Stateless(mappedName = "aja/BookService")
@Local(BookServiceLocal.class)
@Remote(BookServiceRemote.class)
public class BookServiceImpl implements BookService {

@PersistenceContext
EntityManager em;

public void addBook(Book book) {
em.persist(book);
}

@SuppressWarnings("unchecked")
public List getAllBooksByAuthor(Author author) {

Query q = em.createNamedQuery("getAllBooksByAuthor");
q.setParameter("firstName", author.getFirstName());
q.setParameter("lastName", author.getLastName());
return q.getResultList();

}

@SuppressWarnings("unchecked")
public List getAllBooks() {
Query q = em.createNamedQuery("getAllBooks");
return q.getResultList();

}

}

Constructor exception

2011-12-14T00:55:00.003-08:00

Is it possible to create a class which throws an Exception in the constructor. Yes.

The following shows one example.

public class Foo {

public Foo() {

throw new RuntimeException();

}

public void calculate() {

System.out.println("I am now calculating");

}

The class above will always throw a run time exception whenever someone tries to instantiate it. Is there a way round it and call the calculate method? Yes there is. The class below actually succeeds. The solution is that Foo is not a final class. I will sub-class it and operate on that instance.

public class Bar extends Foo {

public static Foo foo;

@Override

protected void finalize() throws Throwable {

foo = this;

}

Create a runner which will do the job.

public class Runner {

public static void main(String...args) {

try {

Foo foo = new Bar();

} catch (Exception e) {

System.out.println("Just to show exception caught " + e.getMessage());

}

System.gc();

System.runFinalization();

System.out.println("My instance " + Bar.foo);

Bar.foo.caluclate());

}

This example shows that you should always use the final word when you do not want people to be able to create incomplete instances.

LifeCycleManagement + JMX

2011-12-14T00:55:00.001-08:00

Sometimes you might want to make sure that when an enterprise application is started, something is executed. This example shows how to do it on a Sun Application Server.

In real life, this example was built with Maven which you will have to configure by yourself if you haven't done it already. But it is only snippets below in the example so no pom.xml files are included. It is not of interest how you build it.

First you must create a web application which is bundled into the ear file. This web application shall contain a web.xml file in the WEB-INF directory. Make sure to include the content below in the file;

**************************************************

org.aja.book.webapp.listener.LifeCycleManager

***************************************************************

In fact, this is the only rows needed in the file. This is our Listener servlet. This will ensure that the application handles this start up in a correct fashion.

Now, create a class, name it LifeCycleManager and make sure it implements the ServletContextListener.

*********************************************************

package org.aja.book.webapp.listener;

import javax.servlet.ServletContextListener;

public class LifeCycleManager implements ServletContextListener {

public void contextDestroyed(ServletContextEvent arg0) {

}

public void contextInitialized(ServletContextEvent arg0) {

}

********************************************************

As you can see two methods needs to be implemented. Now try it. Write a simple System.out and see that it is written out.

You are now done. This shows how you can do it if you need to implement a Listener class.

Step 2

What shall you use this for? Ok, assume you want to have a JMX bean in the application server which you shall access to do stuff. For instance, assume you want to change the log level in run time, you could do this by implementing a JMX bean. Let's do it.

***************************************

You would probably implement a helper class doing all this, but instead I just stash it into the servlet.

In the contextInitialized method do this;

*****************************

Context ic = new InitialContext();

MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
ObjectName name = new ObjectName(
"aja:ear=,jar=aja-startup-ejb-0.1.jar," +
"name=BootStrapImpl,service=EJB3");

BootStrap o = (BootStrap) ic.lookup("aja/BootStrap");
BootStrap mbean = (BootStrap) PortableRemoteObject.narrow(o,
BootStrap.class);

BootStrap mb = new BootStrapImpl();
mbs.registerMBean(mb, name);

mbean.start();

**********************

In the contextDestroyed method do this;

************************************************

Context ic = new InitialContext();

MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
ObjectName name = new ObjectName(
"aja:ear=,jar=aja-startup-ejb-0.1.jar," +
"name=BootStrapImpl,service=EJB3");

BootStrap o = (BootStrap) ic.lookup(aja/BootStrap);
BootStrap mbean = (BootStrap) PortableRemoteObject.narrow(o,
BootStrap.class);

mbs.unregisterMBean(name);
mbean.destroy();

********************************************

This will call our "BootStrap" ejb which initializes some things through the start method(). Also you can add another method called changeLogLevel(int level). Make sure that the names in bold corresponds to your beans name. You can see that in the JMX console if you are unsure.

Thus now you must create three different things;

1) One interface called BootStrap

2) One ejb class called BootStrapImpl

3) One interface extending the BootStrap interface called BootStrapImplMBean

Note here one important thing. It was a bug in the implementation which forced you to create the MBean interface with the same name as the bean with the suffix MBean. Worthless huh! And, you had to have it in the same package as the Bean class as well.

Besides that everything is pretty straighforward;

**************

package org.aja.book.boot;

public interface BootStrap{

void start();

void destroy();

void changeLogLevel(int level);

}

package org.aja.book.boot.impl;

public interface BootStrapImplMBean extends BootStrap {

}

*******************************

Add the BootImpl ejb. Note the completely erroneous use of System.out, should never be used it is just to exemplify here.

*******************************

package org.aja.book.boot.impl;

@EJB

public class BootStrapImpl implements BootStrapImplMBean {

public void start(){

System.out.println("You are now starting");

}

public void destroy(){

System.out.println("You are now destroying");

}

public void changeLogLevel(int logLevel){

System.out.println("You are now trying to change the log level");

}

*******************************

That's it. What happened now was 2 things.

Number one is that your ejb is wrapped as an JMX bean and it has been instantiated and used by the start method. Number 2 is that you through the JMX console you can call the changeLogLevel anytime and change the log level.

The JMX part and the initializtion part has nothing to do with each other, they are just commonly used together that's why I showed them both here.

Good luck.

JAAS and Sun Application Server

2011-12-14T00:54:00.003-08:00

Aha, you to Brutus.

Security, one of the most interesting topics as well as most mythological as well. People tend to get hysterical when it comes to security, especially managers. There are several different ways to do it. In the good old days I remember hwo we made our own cookies and checked for users in files and databases without no standard whatsoever. Now I tend to use JAAS. Here is a small How to implement JAAS.

Everything below is made towards a solution on a Sun Application Server , for JBoss you must pick another how to somewhere else.

Step 1 - Create a authentication realm

asadmin create-auth-realm --classname com.sun.enterprise.security.auth.realm.file.FileRealm --property jaas-context=fileRealm:file=aja_keyfile aja_realm

Step 2 - Create a user to store in the realm

asadmin create-file-user --authrealmname aja_realm --groups aja_admins jonas

You will be promted for a password twice. This will create a new user, "jonas".

Step 3 - List the users in the realm

asadmin list-file-users --authrealmname aja_realm

Step 4 - Delete a user in the realm

asadmin delete-file-user --authrealmname aja_realm

List and delete are really not needed here but can be shown out of interest.

Take a break, you now have a realm and a user.

Step 5 - Create a proper sun-web.xml file

I want include any files since they are so small, but you do like this. Add (if you do not have it already) a sun-web.xml file into the WEB-INF directory of youweb application.

This shall be included

/aja

aja_admins
aja_admins

Keep a copy of the generated servlet class' java code.

Step 6 - Create a proper web.xml file

Include this anywhere in the file;

restricted
/*

aja_admins

unrestricted stylesheets

/css/*
GET

and

FORM
aja_realm

/login/login.html

/login/loginerror.html

aja_admins

one.html

Step 7 - Create a login page

That's it. You are done now.

Step 8 - A note of caution

Please note this fundamentally important thing. If you do have a link to a style sheet in the login page, like

you MUST make sure that that directory is unprotected with an unristricted code block, like the one above. Otherwise you will be re-routed to the style sheet and not to your start page.

JBoss and Basic Authentication

2011-12-14T00:54:00.001-08:00

This is a short how to enable basic auth on a JBoss server and a small test client.

This example is run on Java5, Ubuntu Edgy Eft and JBoss 4.5. It assumes you are working with a web application.

Step 1 Add a jboss-web.xml file to your webapps WEB-INF directory.
Add the following content

< jboss>
< jboss-web>
< security-domain>java:/jaas/myapplication
< /security-domain>
< /jboss-web>
< /jboss>

Change your web.xml file and add the following rows.
< security-constraint>
< web-resource-collection>
< web-resource-name>UserResources
< description>
/services/*

< auth-constraint>
< role-name>user

< security-role>
< role-name>user

< security-role>
< role-name>operator

< security-role>
< role-name>admin

< login-config>
< auth-method>BASIC
< realm-name>MyApplicationRealm

Change some files on your JBoss application server files.
Change the file login-config.xml in the conf directory.
< application-policy name="myapplication">
< authentication>
< login-module code="org.jboss.security.auth.spi.UsersRolesLoginModule"
flag = "required">
< module-option name="usersProperties">props/rk-users.properties
< module-option name="rolesProperties">props/rk-roles.properties

Create two new files in the conf/props.

One file with the users called rk-users.properties

Add the following user

admin=adminpwd

One file with the roles called rk-roles.properties

Add the following roles

admin=sysadmin,user

I made a xfire client calling my xfire web services. see xfire codehaus for an examle on a web client.

Then add these lines of code

org.codehaus.xfire.client.Client client = org.codehaus.xfire.client.Client.getInstance(service);

client.setProperty(Channel.USERNAME, "admin");

client.setProperty(Channel.PASSWORD, "adminpwd");

Ws security and Jax WS

2011-12-14T00:53:00.000-08:00

I had some annoying problems with the WS security examples found on the net. I had an application which simply refused to pass along the header data as they should. I followed every tutorial available and did like this;

bp.getRequestContext().put(javax.xml.ws.BindingProvider.USERNAME_PROPERTY, "admin");

bp.getRequestContext().put(javax.xml.ws.BindingProvider.PASSWORD_PROPERTY,"adminpwd")

So I had to make the header of the request myself. This is how I did it. As always, even though it doesn't matter I made it in Eclipse building it in Maven.

Server files

On the server side a made on class, call it Service.

@WebService

@HandlerChain(file="MyChain.xml")

public class Service {

@WebMethod

public String getName(){

return "King Kong";

}

Note that the file path is relative so for simplicity I just put the file (MyChain.xml) in the same directory as this file, i.e. in the source package.

Thexml file just contain a pointer towards a handler.

com.aja.util.MySOAPHandler

Now we only lack the handler class.

*****************************************************

package com.aja.util;

/**

import java.io.PrintStream;
import java.util.Map;
import java.util.Set;

import javax.xml.namespace.QName;
import javax.xml.soap.SOAPMessage;
import javax.xml.ws.handler.MessageContext;
import javax.xml.ws.handler.soap.SOAPHandler;
import javax.xml.ws.handler.soap.SOAPMessageContext;

import java.io.PrintStream;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.xml.soap.SOAPEnvelope;
import javax.xml.soap.SOAPHeader;
import javax.xml.soap.SOAPMessage;
import javax.xml.soap.SOAPPart;
import javax.xml.ws.handler.Handler;
import javax.xml.ws.handler.MessageContext;
import javax.xml.ws.handler.soap.SOAPMessageContext;

import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class MySOAPHandler implements SOAPHandler
{
private static final String WS_SEC = "wsse:Security";
private static final String WSSE_USERNAME = "wsse:Username";
private static final String WSSE_PASSWORD = "wsse:Password";

protected PrintStream out = System.out;

protected String HandlerName = "Handler";

@PostConstruct
public void init()
{
}

@PreDestroy
public void destroy()
{
}

/**
* {@inheritDoc}
*/
public void close(@SuppressWarnings("unused")
MessageContext context)
{
}

/**
* {@inheritDoc}
*/
@SuppressWarnings("unchecked")
public boolean handleMessage(SOAPMessageContext messagecontext)
{

try
{
SOAPMessage message = messagecontext.getMessage();
SOAPPart part = message.getSOAPPart();
SOAPEnvelope envelope = part.getEnvelope();
SOAPHeader header = envelope.getHeader();
String username;
String password;

Element sec = null;

for (Iterator k = header.getChildElements(); k.hasNext();)
{
Element element = k.next();
if (element.getNodeName().equals(WS_SEC))
{
sec = element;

NodeList e = sec.getElementsByTagName(WSSE_USERNAME);

Node tok = e.item(0);

NodeList child = tok.getChildNodes();
if (child != null)
{
username = child.item(0).getNodeValue();
if (!(username.equals("admin")))
{
return false;
}
}

NodeList f = sec.getElementsByTagName(WSSE_PASSWORD);

Node t = f.item(0);
NodeList c = t.getChildNodes();
if (c != null)
{
password = c.item(0).getNodeValue();
if (!(password.equals("adminpwd")))
{
return false;
}
}

}
}

}
catch (Exception e)
{
return false;
}

return true;

}

/**
* Subclassing children of this method will determine if to process the
* request.
*
* @return True if we are to continue with authentication, false otherwise.
*/
protected boolean doAuthentication()
{
return true;
}

/**
* When the userid and password is extracted from the request it will call
* this method and return the value returned by this method.
*
* @param userName
* The username extracted from the request.
* @param password
* The password extracted from the request.
* @return See method description on this method.
*/
protected boolean isValidAuthentication(String userName, String password)
{
return true;
}

/**
* {@inheritDoc}
*/
public Set getHeaders()
{
// TODO Auto-generated method stub
return null;
}

/**
* {@inheritDoc}
*/
public boolean handleFault(SOAPMessageContext arg0)
{
// TODO Auto-generated method stub
return false;
}
}
***************************************************

This method can be tested by SOAP UI by sending this request, try to change the pwd and you will be rejected.

*****************************************************

admin
adminpwd

********************************************************

Client files

Make a similar handler file, I don't use the same sice the client is separate from the server. Call it ClientHandler.xml

****************

com.aja.client.Handler

******************************************

Make the handler file, Handler.java.

*******************************************

package com.aja.client;

import java.util.Set;

import javax.xml.namespace.QName;
import javax.xml.soap.Name;
import javax.xml.soap.SOAPElement;
import javax.xml.soap.SOAPEnvelope;
import javax.xml.soap.SOAPFactory;
import javax.xml.soap.SOAPHeader;
import javax.xml.soap.SOAPHeaderElement;
import javax.xml.soap.SOAPMessage;
import javax.xml.soap.SOAPPart;
import javax.xml.ws.handler.MessageContext;
import javax.xml.ws.handler.soap.SOAPHandler;
import javax.xml.ws.handler.soap.SOAPMessageContext;

public class Handler implements SOAPHandler
{

private static final String WSSE = "wsse";
private static final String WS_SEC = "Security";
private static final String USERNAME_TOKEN = "UsernameToken";
private static final String USERNAME = "Username";
private static final String PASSWORD = "Password";
private static final String NAME_SPACE_URI = "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd";

public SecurityHandler()
{
}

public Set getHeaders()
{
return null;
}

public boolean handleFault(SOAPMessageContext messageContext)
{
return true;
}

public boolean handleMessage(SOAPMessageContext messageContext)
{
secureClient(messageContext);
return true;
}

public void close(MessageContext messageContext)
{
}

private void secureClient(SOAPMessageContext messageContext)
{
try
{
SOAPMessage message = messageContext.getMessage();
SOAPPart part = message.getSOAPPart();
SOAPEnvelope envelope = part.getEnvelope();
SOAPHeader header = envelope.getHeader();

if (header == null)
{
header = envelope.addHeader();
}

SOAPFactory factory = SOAPFactory.newInstance();

Name security = factory.createName(WS_SEC, WSSE, NAME_SPACE_URI);
SOAPHeaderElement orderHeader = header.addHeaderElement(security);

Name userNameToken = factory.createName(USERNAME_TOKEN, WSSE,
NAME_SPACE_URI);
Name user = factory.createName(USERNAME, WSSE, NAME_SPACE_URI);
Name pwd = factory.createName(PASSWORD, WSSE, NAME_SPACE_URI);

SOAPElement elem = orderHeader.addChildElement(userNameToken);
SOAPElement userElement = elem.addChildElement(user);
userElement.addTextNode("admin");
SOAPElement pwdElement = elem.addChildElement(pwd);
pwdElement.addTextNode("adminpwd");
}
catch (Exception e)
{
System.out.println("Exec " + e.getMessage());

}

}
}

****************************************************************

And finally hook up to the file every time a web service request is called. I added this where I receive my web service client.

********************************************

@HandlerChain(file="ClientHandler.xml")

public class MyClient {

}

************************************************

In the example above the manager is an instance of my web service cleint part. This is autogenerated by maven with the wsgen and wsimport commands.

Double checked locking

2011-12-14T00:52:00.002-08:00

Read this small good article about double checked locking.

Java threads

2011-12-14T00:52:00.001-08:00

Threads, a topic causing people to become dazed and confused. In general, a difficult topic to grasp. Many persons implementing JavaEE applications never bother with Threads and synchronization. Below are some discussions and examples around Threads and what they are.

Multi threading refers to how to handle two or more tasks occurring "simultaneously" in an application.Thus for instance, assume that one person writes data to a object then a threaded application may prevent another user to read the data before the write has succeeded.

We will show three objects and their methods of interest

Object

notify()

notifyAll()

wait()

wait(long)

wait(long, int)

Thread

sleep()

yield()

run()

sleep(long)

Runnable

run()

I will try to avoid to dig to much into the deep of all this, instead just go give some highlights of some things.

Below is the simplest start.

public class MyRunnable implements Runnable {

 Thread runner;
 public RunnableThread() {
 }
 public RunnableThread(String threadName) {
  runner = new Thread(this, threadName); 
  System.out.println(runner.getName());
  runner.start(); 
 }
 public void run() {
   System.out.println(Thread.currentThread());
 }
}

public class RunnableExample {

 public static void main(String[] args) {
  Thread thread1 = new Thread(new MyRunnable (), “thread1″);
  Thread thread2 = new Thread(new MyRunnable (), “thread2″);
  //Start the threads
  thread1.start();
  thread2.start();
  try {
   //delay for one second
   Thread.currentThread().sleep(1000);
  } catch (InterruptedException e) {
  }
  System.out.println(Thread.currentThread());
 }
}

Implement the Runnable interface in those cases when you want your class to only use the Run method and you want it to be able to extend another class. Do not call the run() method, insted you must just the start() method. If you want the full Monty you will need to exetnd the Thread class, as below.

public class MyThread extends Thread {

 MyThread (String threadName) {
  super(threadName); 
  start();
 }
 public void run() {
  System.out.println(Thread.currentThread().getName());
 }
}

public class ThreadExample {

 public static void main(String[] args) {
  Thread thread1 = new MyThread ("A");
  Thread thread2 = new MyThread("B");
  Thread thread3 = new MyThread(”C″);
  //Start the threads
  thread1.start();
  thread2.start();
  thread3.start();
  try {
   Thread.currentThread().sleep(1000);
  } catch (InterruptedException e) {
  }
  System.out.println(Thread.currentThread());
 }
}

Sleep causes the current thread to suspend execution for a specified period. For instance assume you really want to wait a number of milliseconds before trying again. An example might be that you do not have a call back functionality, instead you poll. Say for instance, you see if a log file has changed it's time stamp, and you do it every 10 seconds.

Non synchronization

public class Counter {
   private int c = 0;

   public void increment() {
       c++;
   }

   public void decrement() {
       c--;
   }

   public int value() {
       return c;
   }

}

Interference happens when two operations, running in different threads, but acting on the same data, interleave. This means that the two operations consist of multiple steps, and the sequences of steps overlap.

Synchronized methods

public class SynchronizedCounter {
   private int c = 0;

   public synchronized void increment() {
       c++;
   }

   public synchronized void decrement() {
       c--;
   }

   public synchronized int value() {
       return c;
   }
}

Read and understand the below statement and you will understand what all is about;

First, it is not possible for two invocations of synchronized methods on the same object to interleave. When one thread is executing a synchronized method for an object, all other threads that invoke synchronized methods for the same object block (suspend execution) until the first thread is done with the object.
Second, when a synchronized method exits, it automatically establishes a happens-before relationship with any subsequent invocation of a synchronized method for the same object. This guarantees that changes to the state of the object are visible to all threads.

Synchronized statements

public class MsLunch {
   private long c1 = 0;
   private long c2 = 0;
   private Object lock1 = new Object();
   private Object lock2 = new Object();

   public void inc1() {
       synchronized(lock1) {
           c1++;
       }
   }

   public void inc2() {
       synchronized(lock2) {
           c2++;
       }
   }
}

Synchronized statements are useful for improving concurrency with fine-grained synchronization.

Re-cap

Locks are used to synchronize access to a shared resource. A lock can be associated with a shared resource.
Threads gain access to a shared resource by first acquiring the lock associated with the object/block of code.
At any given time, at most only one thread can hold the lock and thereby have access to the shared resource.

This will in the practical world means these two things;

If you put synchronized on a static method ALL requests will wait (queue) when a call is made to that method since ALL requests use the same static method.
If you put synchronized on an instance method ALL requests will wait (queue) when a call is made to the same instance method. Thus if each request call a new instance and only one method is synchronized it is useless. You do not need to synchronize in that case.

The great misunderstanding

Many people do not understand that this has the same meaning,

public synchronized String getName() {

   return "x";

same as;

public String getName() {

  synchronized(this) {

  return "x";

It is the same, all requests on the same instance of the class will wait in a queue when the method getName is called.

RMI

2011-12-14T00:51:00.002-08:00

Java R(emote) M(ethod) I(nvocation) is a feature that has had a shrinking part of distributed applications over the last years. Both EJB 3.0 with its simplicity and web services has superseded RMI. Naturally EJB uses RMI under the hood, but I am here more concerened with pure RMI. Most of the below examples are taken from the Sun page.

In brief to get RMI to work, you need to have a Registry accepting calls.In the LocalRegistryAPI this text can be found;

"LocateRegistry iis used to obtain a reference to a bootstrap remote object registry on a particular host (including the local host), or to create a remote object registry that accepts calls on a specific port."

So we need this architecture to get it to work;

The picture explains everything pretty well.

We need the following files;

An object to pass between the client and the server, this object will implement the Task interface.

package compute;

public interface Task {
   T execute();
}

A remote interface to use by our class acting as a server, the interface is Compute.

package compute;

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface Compute extends Remote {
    T executeTask(Task t) throws RemoteException;
}

Server side, create a registry and accept calls on ports 1199.

package engine;

import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
import compute.Compute;
import compute.Task;

public class ComputeEngine implements Compute {

   public ComputeEngine() {
       super();
   }

   public  T executeTask(Task t) {
       return t.execute();
   }

    public static void main(String[] args) {
       if (System.getSecurityManager() == null) {
           System.setSecurityManager(new SecurityManager());
       }
       try {
           LocateRegistry.createRegistry(1199);
           String name = "Compute";
           Compute engine = new ComputeEngine();
           Compute stub =
               (Compute) UnicastRemoteObject.exportObject(engine, 0);
            Registry registry = LocateRegistry.getRegistry(1199);
           registry.rebind(name, stub);
           System.out.println("ComputeEngine bound");
       } catch (Exception e) {
           System.err.println("ComputeEngine exception:");
           e.printStackTrace();
       }
   }
}

Client side, first class implementing Task

package client;

import compute.Task;
import java.io.Serializable;
import java.math.BigDecimal;

public class Pi implements Task, Serializable {

   private static final long serialVersionUID = 227L;

   /** constants used in pi computation */
   private static final BigDecimal FOUR =
       BigDecimal.valueOf(4);

   /** rounding mode to use during pi computation */
   private static final int roundingMode =
       BigDecimal.ROUND_HALF_EVEN;

   /** digits of precision after the decimal point */
   private final int digits;
  
   /**
    * Construct a task to calculate pi to the specified
    * precision.
    */
   public Pi(int digits) {
       this.digits = digits;
   }

   /**
    * Calculate pi.
    */
   public BigDecimal execute() {
       return computePi(digits);
   }

   /**
    * Compute the value of pi to the specified number of
    * digits after the decimal point.  The value is
    * computed using Machin's formula:
    *
    *          pi/4 = 4*arctan(1/5) - arctan(1/239)
    *
    * and a power series expansion of arctan(x) to
    * sufficient precision.
    */
   public static BigDecimal computePi(int digits) {
       int scale = digits + 5;
       BigDecimal arctan1_5 = arctan(5, scale);
       BigDecimal arctan1_239 = arctan(239, scale);
       BigDecimal pi = arctan1_5.multiply(FOUR).subtract(
                                 arctan1_239).multiply(FOUR);
       return pi.setScale(digits,
                          BigDecimal.ROUND_HALF_UP);
   }
   /**
    * Compute the value, in radians, of the arctangent of
    * the inverse of the supplied integer to the specified
    * number of digits after the decimal point.  The value
    * is computed using the power series expansion for the
    * arc tangent:
    *
    * arctan(x) = x - (x^3)/3 + (x^5)/5 - (x^7)/7 +
    *     (x^9)/9 ...
    */  
   public static BigDecimal arctan(int inverseX,
                                   int scale)
   {
       BigDecimal result, numer, term;
       BigDecimal invX = BigDecimal.valueOf(inverseX);
       BigDecimal invX2 =
           BigDecimal.valueOf(inverseX * inverseX);

       numer = BigDecimal.ONE.divide(invX,
                                     scale, roundingMode);

       result = numer;
       int i = 1;
       do {
           numer =
               numer.divide(invX2, scale, roundingMode);
           int denom = 2 * i + 1;
           term =
               numer.divide(BigDecimal.valueOf(denom),
                            scale, roundingMode);
           if ((i % 2) != 0) {
               result = result.subtract(term);
           } else {
               result = result.add(term);
           }
           i++;
       } while (term.compareTo(BigDecimal.ZERO) != 0);
       return result;
   }
}

And then client calling server and passing object.

package client;

import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.math.BigDecimal;
import compute.Compute;

public class ComputePi {
   public static void main(String args[]) {
       if (System.getSecurityManager() == null) {
           System.setSecurityManager(new SecurityManager());
       }
       try {
           String name = "Compute";
           Registry registry = LocateRegistry.getRegistry(1199);
           Compute comp = (Compute) registry.lookup(name);
           Pi task = new Pi(Integer.parseInt(45);
           BigDecimal pi = comp.executeTask(task);
           System.out.println(pi);
       } catch (Exception e) {
           System.err.println("ComputePi exception:");
           e.printStackTrace();
       }
   }   
}

You must now add two security files, server.policy to the server project and client.policy to he client project.

My files are identivcal in appearence and look like this;

grant {
permission java.security.AllPermission;
};

Add them to your runtime environment by doing this in both the server and the client project.

In the client project the VM option should be -Djava.security.policy=client.policy and in the server project -Djava.security.policy=server.policy

JAAS and Derby

2011-12-14T00:51:00.001-08:00

Did you read the previous document about JAAS and Sun Application Server? That implemented a file

based JAAS security handling. I wanted to experiment with a database solution which in my humble opinion is better,

since it more distributable (to name just one advantage)

To give credit where it is due, it took almost everything form here.

You only need to do four things, and those are quite simple.

Fix database

I use to default tablespace that comes with the Derby database. That is in the latest versions of Java a Derby database is shipped.

The standard way to work with it is to start it either from the application servers asadamin, with command, asadmin start-database or stand alone.

This is the necessary data you need by default

url: jdbc:derby://localhost:1527/sun-appserv-samples

uid: APP

pwd: APP

A connection pool is set up in the Application Server that goes towards this database. You do not need to do anything besides start the app server.

Just run these and everything will be ok. Then your database will be populated with the correct tables.

create table usertable(userid varchar(10) not null,
password varchar(32) not null, primary key(userid));
create table grouptable(userid varchar(10) not null,
groupid varchar(20) not null, primary key(userid));
alter table grouptable add constraint FK_USERID
foreign key(userid) references usertable(userid);

Note that the default handling of pwd will be hex so you cannot add a plain text password manually
into the database. This will fail. 

Thus, log into the Derby database, with squirrel or something else. Then execute the three scripts above.

Create realm in Sun Application Server
Create this realm in the admin console. You do this by doing this;

log in to admin console with http://localhost:4848, go to
Configuration->Security->Realms. Since I had created my realm previously I saw it here. If you haven't
just create a new one here.
Make sure that className is JdbcRealm. Then a lot of textboxes will appear. Fill in those so that they look like below.

`Property Name`	`Property Value`
`datasource-jndi`	`jdbc/security`
`user-table`	`usertable`
`user-name-column`	`userid`
`password-column`	`password`
`group-table`	`grouptable`
`group-name-column`	`groupid`
`jaas-context`	`jdbcRealm`

Add the html files
In the previous example we added the necessary files, but here is a replay.




Sun-web.xml file

These files indicate the userid and groupid.




 /WebApplication1
 
   jonas_admins
   jonas
   
 
 
 
   
     Keep a copy of the generated servlet class' java code.
   
 



login.html


 
   
   
 
 
                       



                           User Name: 
                           Password : 
                            
                           
                       

                   



index.jsp
<%@page contentType="text/html" pageEncoding="UTF-8"%>



   
       
       JSP Page
   
   
       Hello World!

   


web.xml


   
       
           30
       
   
   
       index.jsp
       
       
       
           restricted
           /*
       
       
           jonas_admins
          
   




       
           
               unrestricted stylesheets
           
           /css/*
           GET
       
   


       FORM
       jonas_realm
       
           /login.html
           
               /loginerror.html
           
       
   

   
       jonas_admins
   
   


That's it. Just deploy the app and it will work. You will be forced to add a uid/pwd to be accepted.
The file to add users/pwds in the database in hex format can be found below, taken from Sun.



File to populate database with pwd in hex

import java.security.MessageDigest;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

public class CreateJdbcRealmUser {
   private static final String driver = "org.apache.derby.jdbc.ClientDriver";
   private static final String jdbcUrl = "jdbc:derby://localhost:1527/sun-appserv-samples";
   private static final String userSql = "insert into usertable values(?, ?)";
   private static final String groupSql = "insert into grouptable values(?, ?)";

   private static final char[] HEXADECIMAL = { '0', '1', '2', '3',
       '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

   private static String hashPassword(String password) throws Exception {
       MessageDigest md = MessageDigest.getInstance("MD5");
       md.reset();

       byte[] bytes = md.digest(password.getBytes());
       StringBuilder sb = new StringBuilder(2 * bytes.length);
       for (int i = 0; i < bytes.length; i++) {
           int low = (int)(bytes[i] & 0x0f);
           int high = (int)((bytes[i] & 0xf0) >> 4);
           sb.append(HEXADECIMAL[high]);
           sb.append(HEXADECIMAL[low]);
       }
       return sb.toString();
   }

   public static void main(String args[]) throws Exception {
       String dbUser = null;
       String dbPassword = null;
       String user = null;
       String password = null;
       String group = null;

       if (args.length != 5){
           System.err.println("Usage java CreateJDBCRealmUser     ");
           System.exit(2);
       } else {
           dbUser = args[0];
           dbPassword = args[1];
           user = args[2];
           password = args[3];
           group = args[4];
       }

       Class.forName(driver);
       String hPassword = hashPassword(password);
       Connection conn = DriverManager.getConnection(
           jdbcUrl, dbUser, dbPassword);
       PreparedStatement userStmt = conn.prepareStatement(userSql);
       userStmt.setString(1, user);
       userStmt.setString(2, hPassword);
       userStmt.executeUpdate();
       userStmt.close();

       PreparedStatement groupStmt = conn.prepareStatement(groupSql);
       groupStmt.setString(1, user);
       groupStmt.setString(2, group);
       groupStmt.executeUpdate();
       groupStmt.close();

       conn.close();
   }
}

Java is pass by value

2011-12-14T00:49:00.004-08:00

First a definition so everything is clear.

Pass by value - The actual value of a parameter is copied into a "new" memory address and any manipulation of this value will not cause the original value to change. Every call to the method will create a new parameter with a new value which is uniquely changed in the method.

Pass by reference - The parameter is just an alias for the actual value. every time the alias is used the real value is actually used. Thus a change to the value in the method will change the value of the object if it is called from outside the method as well.

Java is pass by value. See the formal explanation here.

Why the confusion then?

Well because even though in a formal sense Java is pass by value there are some instances where the result seem to contradict this. For all you zealots out there, I know the differenceon pass by value/reference and the below example is merely to show why some people have a hard time to grasp this. In a formal sense this is pass by value even though the result is "odd".

First a small pojo.

******************************

public class A
{
private String name;
private int age;
/**
* @return the name
*/
public String getName()
{
return name;
}
/**
* @param name the name to set
*/
public void setName(String name)
{
this.name = name;
}
/**
* @return the age
*/
public int getAge()
{
return age;
}
/**
* @param age the age to set
*/
public void setAge(int age)
{
this.age = age;
}
}

*********************************

The a class using this pojo.

**********************************

public class Runner
{

/**
* @param args
*/
public static void main(String[] args)
{
Runner r = new Runner();
r.init();
}

private void init(){

A a = new A();
a.setName("King");
a.setAge(25);

System.out.println("A name before method call" + a.getName());
System.out.println("A age before method call" + a.getAge());

this.changeValue(a);

System.out.println("A name after method call" + a.getName());
System.out.println("A age after method call" + a.getAge());

}

private void changeValue(final A a){

a.setName("Kong");
a.setAge(35);

System.out.println("A name in method: " + a.getName());
System.out.println("A age in method: " + a.getAge());
}

}

*********************************************

The output on the screen is

A name before method callKing
A age before method call25
A name in method: Kong
A age in method: 35
A name after method callKong
A age after method call35

*************************************************

Now from my point of view this looks like some kind of reference. And here is the rather dubious part of this,

Object references are passed by value.

Read that again. It is fundamental. It is actually the "pointer" towards the memory address which is copied and sent to the method as a formal parameter. this means that all changes inside the object is actully propagated outside of the method.

OK but what about this?

private void changeValueComplex(final A a){

A b = a;
b.setName("Jonas");
b.setAge(35);

System.out.println("B name in method: " + b.getName());
System.out.println("A name in method: " + a.getName());
System.out.println("B age in method: " + b.getAge());
System.out.println("A age in method: " + a.getAge());
}

********************

Sorry mate, no use. Same result. Hrm what to do. Wait, I got it!

Add this to A:

implements Cloneable

and this method

public Object clone() throws CloneNotSupportedException {
return (A) super.clone();
}

private void changeValueByClone(final A a){

try {
A b = (A)a.clone();
b.setName("Jonas");
b.setAge(35);

System.out.println("B name in method: " + b.getName());
System.out.println("A name in method: " + a.getName());
System.out.println("B age in method: " + b.getAge());
System.out.println("A age in method: " + a.getAge());
}catch (Exception e){
e.printStackTrace();
}

}

Now we actually could manipulate the values in one object without affecting the other one.

Remote EJB call in Glassfish

2011-12-14T00:49:00.003-08:00

Properties props = new Properties();
props.setProperty("java.naming.factory.initial",
"com.sun.enterprise.naming.SerialInitContextFactory");
props.setProperty("java.naming.factory.url.pkgs",
"com.sun.enterprise.naming");
props.setProperty("java.naming.factory.state",
"com.sun.corba.ee.impl.presentation.rmi.JNDIStateFactoryImpl");

props.setProperty("org.omg.CORBA.ORBInitialHost", "localhost");
props.setProperty("org.omg.CORBA.ORBInitialPort","3700");

try
{
Context ic = new InitialContext(props);
ServiceRemote remote = (ServiceRemote ) ic
.lookup("aja/ServiceBean");
remote.lala();

}
catch (Exception e)
{

}

Create a stateless bean and do like this

@Stateless(mappedName="aja/ServiceBean")

public ServiceBean implements ServiceRemote

wsimport and wsgen

2011-12-14T00:49:00.001-08:00

Difference between ws-import and ws-gen.

wsimport - The wsimport command-line tool supports the top-down approach to developing JAX-WS Web services. When you start with an existing WSDL file, use the wsimport command-line tool to generate the required JAX-WS artifacts.

wsgen - When using a bottoms-up approach to develop JAX-WS Web services and you are starting from a service endpoint implementation, use the wsgen tool to generate the required JAX-WS artifacts.

A great article combining maven/NetBeans with the above tools can be found here. And mind you, it actually works right out of the box.

Jax-RS

2011-12-14T00:48:00.001-08:00

This is just a placeholder for a longer article. Use this link as of now.

Jax WS small annotated class

2011-12-14T00:47:00.001-08:00

package helloservice.basicauth.endpoint;

import javax.jws.WebMethod;
import javax.jws.WebService;
import javax.annotation.security.RolesAllowed;

@WebService
public class Hello {
private String message = new String("Hello, ");

@WebMethod
@RolesAllowed("msa_admins")
public String sayHello(String name) {
return message + name + ".";
}
}

Java runtime

2011-12-14T00:46:00.003-08:00

First, java.exe does not take a directory structure to start, rather it takes the name of the class. You can speficy the classpath if you don't want . as the classpath.

E.g.

To run your Temp_prog from Current you could use:
java -classpath Sub Temp_prog
or
java -classpath c:\Current\Sub Temp_prog

if Temp_Prog was actually defined in the package Sub then you could execute:
java Sub.Temp_prog
or
java -classpath c:\Current Sub.Temp_prog

You could also call the programs main directly if its in the classpath
e.g.
java -classpath .;Sub Cur_prog
And in your class,
Temp_Prog.main(new String[]{"Arg1,"Arg2"});

If you really do want to change the current directory, then you could just use the 3 argument version of exec
e.g.
Runtime.getRuntime().exec("

java Temp_prog",null,new File("Sub"));

Microscopic small JPA class

2011-12-14T00:46:00.001-08:00

import javax.annotation.Resource;
import javax.naming.Context;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@PersistenceContext(name = "persistence/LogicalName",
unitName = "jpawebPU")
public class CustomerDAO {
@Resource
private javax.transaction.UserTransaction utx;
protected void persist(Object object) {

try {
Context ctx =
(Context) new javax.naming.InitialContext().
lookup("java:comp/env");
utx.begin();
EntityManager em = (EntityManager)
ctx.lookup("persistence/LogicalName");

em.persist(object);
utx.commit();
} catch (Exception e) {
java.util.logging.Logger.getLogger(
getClass().getName()).log(
java.util.logging.Level.SEVERE,
"exception caught", e);
throw new RuntimeException(e);

}
}
}

See this link.

Login

2011-12-14T00:45:00.003-08:00

package guessNumber;

import java.io.IOException;
import java.net.

MalformedURLException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

/**
* A filter which is located "on-top" of the j_security_check made by Glassfish
* server when the user is trying to access a restricted webresource.
* This filter creates Login jobs. Logout jobs are created by the MsaWebSessionListener
* class.
*
* @author Ericsson MIEP Team
* @since Dec 1, 2008
*/
public class LoginFilter implements Filter
{
protected FilterConfig filterConfig = null;

/**
* {@inheritDoc}
*/
public void init(FilterConfig config) throws ServletException
{
this.filterConfig = config;
}

/**
* {@inheritDoc}
*/
public void destroy()
{
}

/**
* {@inheritDoc}
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException
{
HttpServletRequest httpRequest = null;

if (!(request instanceof HttpServletRequest))
{
chain.doFilter(request, response);
return;
}

httpRequest = (HttpServletRequest) request;
HttpSession session = httpRequest.getSession();
String remoteUser = httpRequest.getRemoteUser();

chain.doFilter(request, response);
}

}

i web.xml

LoginFilterfilter-name>

guessNumber.LoginFilter

LoginFilterfilter-name>

JAX RS

2011-12-14T00:45:00.001-08:00

This example is taken from the MyEclipse web site.

3 things needed to get it to work.

web.xml

***********************************

JAX-RS REST Servlet
JAX-RS REST Servlet

com.sun.jersey.spi.container.servlet.ServletContainer

1

JAX-RS REST Servlet
/services/*

index.jsp

*******************************************************

A service annotated properly.

package com.myeclipseide.ws;

import java.util.ArrayList;
import java.util.List;
import java.util.TreeMap;

import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;

import com.sun.jersey.spi.resource.Singleton;

@Produces("application/xml")
@Path("customers")
@Singleton
public class CustomerResource {

private TreeMap customerMap = new TreeMap();

public CustomerResource() {
Customer customer = new Customer();
customer.setName("Harold Abernathy");
customer.setAddress("Sheffield, UK");
addCustomer(customer);
}

@GET
public List getCustomers() {
List customers = new ArrayList();
customers.addAll(customerMap.values());
return customers;
}

@GET
@Path("{id}")
public Customer getCustomer(@PathParam("id") int cId) {
return customerMap.get(cId);
}

@POST
@Path("add")
@Produces("text/plain")
@Consumes("application/xml")
public String addCustomer(Customer customer) {
int id = customerMap.size();
customer.setId(id);
customerMap.put(id, customer);
return "Customer " + customer.getName() + " added with Id " + id;
}
}

*****************

An entity to work with

package com.myeclipseide.ws;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Customer {

private int id;
private String name;
private String address;

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}

}

*************************

That's it. You will need some jars implementing the rs api.

Derby with JUnit

2011-12-14T00:44:00.001-08:00

package xxx;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.List;
import java.util.Properties;

import org.jmock.Mockery;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class A {

Mockery context = new Mockery();

private String protocol = "jdbc:derby:";
private Connection conn;

String strUrl = "jdbc:derby:DefaultAddressBook;create=true";

private String strCreateAddressTable =
"CREATE table APP.BAPOR (ID INTEGER NOT NULL PRIMARY KEY GENERATED ALWAYS AS IDENTITY"
+ "(START WITH 1, INCREMENT BY 1),"
+ "LASTNAME VARCHAR(30))";

@Before
public void setUp() throws Exception {
super.setUp();

String userHomeDir = System.getProperty("user.home", ".");
String systemDir = userHomeDir + "/.addressbook";

// Set the db system directory.
System.setProperty("derby.system.home", systemDir);

Properties props = new Properties();
props.put("user", "dbuser");
props.put("password", "dbuserpwd");

String driver = "org.apache.derby.jdbc.EmbeddedDriver";
Class.forName(driver).newInstance();

conn = DriverManager.getConnection(strUrl, props);
Statement statement = conn.createStatement();
//statement.execute(strCreateAddressTable);

// DriverManager.getConnection("jdbc:derby:;shutdown=true") &&
//this.createTables(conn);
//this.insert();
this.select();
System.out.println("jjjjjj");
}

@Test
public void testDummy() throws Exception {

}

@After
public void tearDown() {
try {

//DriverManager.getConnection("jdbc:derby:DefaultAddressBook;shutdown=true");

} catch (Exception e) {
e.printStackTrace();
}
}

public void insert() {

Statement stmt = null;
try {
stmt = conn.createStatement();
stmt.executeUpdate("INSERT INTO APP.BAPOR( LASTNAME ) VALUES ( 'Kungen' ) ");
stmt.close();
} catch (Exception e) {
e.printStackTrace();
}
}

public void select() {

Statement stmt = null;
try {
stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM APP.BAPOR");

while (rs.next()) {
int numColumns = rs.getMetaData().getColumnCount();
for (int i = 1; i <= numColumns; i++) {
// Column numbers start at 1.
// Also there are many methods on the result set to return
// the column as a particular type. Refer to the Sun
// documentation
// for the list of valid conversions.
System.out.println("COLUMN " + i + " = " + rs.getObject(i));
}
}

rs.close();

stmt.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}

Glassfish remote debugging

2011-12-14T00:43:00.002-08:00

I did this to get my glassfish up and running and enabled for jmx remote connection.

Check this line in the domains/domain1/config/domain.xml

and change false to true.

Add this line.

-Djava.rmi.server.hostname=

In the log domains/domain1/logs/server.log you will see a log statement lookling like this that shows that jmx is activated, it looks like this

service:jmx:rmi:///jndi/rmi://:8686/jmxrmi

Verify that you can connect with this connection string in jconsole

service:jmx:rmi:///jndi/rmi://:8686/jmxrmi

uid and pwd is by default admin/adminadmin

Ruby On Rails (Install on Ubuntu)

2011-12-14T00:43:00.001-08:00

How to install Ruby on Rails on Ubuntu 9.04

sudo apt-get install ruby1.8-dev
sudo apt-get install rubygems
gem install rails (Didn't help me. Claims it did not find rails afterwards.)
sudo apt-get install rails
rails blog
cd blog
sudo gem install sqlite3-ruby (generates a lot of errors)
rake db:create (generate warnings)
vi app/views/home/index.html.erb (and edit the file)
script/generate controller home index (generates warnings)
script/server
Go to http://127.0.0.1:3000/ (In browser it shows start page.)
Go to http://localhost:3000/home/index and see the default index file that is created at the beginningand which you edited.

This is it.

Netbeans and Google App engine

2011-12-14T00:42:00.001-08:00

Interested in the cloud? Well, besides using gmail and google docs and stuff like that. It has been possible for a while to upload web applications onto Googles servers.

Step 1: Sign up for a Google App engine account
Navigate here http://appengine.google.com and create an account if you do not have it already.

Step 2: Create an application by browsing here, https://appengine.google.com/start/createapp.
I named my first application just aspemo. Thus, my finished application url will be http://aspemo.appspot.com/ .

Step 3: Install the Google app sdk
Go here and download the sdk, http://code.google.com/appengine/downloads.html#Download_the_Google_App_Engine_SDK.
I am more familiar with Java than with Python so I use my Java sdk to do this.

Step 4: Download the Netbeans IDE.

Step 5: Install the Google app plugin for Netbeans.
Go here and follow the instructions (only two lines).

Step 6: Install Google App engine as a service
Go to the folder services (in Netbeans) and choose Server and add a new Google App engine. Point it towards your installation of the Google sdk.

Step 7: Build the guestbook application
Go inot Netbeans and choose;
File->New Project
Samples->Google App Engine
Remember to change the application tag in the applicationContext.xml file to be the same as the application name you used in Google App Engine. In my case, I must change this to aspemo.
Now right click on the project gusetbook and do clean and build followed by deploy to Google App Engine. You will be promted for credentials. Your app should be found in your http://.appspot.com.
My app can be found at http://aspemo.appspot.com
Click the green run button when you are done.

Then I used netbeans to create my sample application. Remember to name your application (in the appengine-web.xml file) with the same name as you created the application with on Google app enging.

Subversion and svnsync and websvn

2011-12-14T00:41:00.001-08:00

This tutorial shows how to syncronzie your own local repository with a remote repository and sync with it. The result shall be displayed in the websvn GUI. How to add basic security is shown in apache2 and basic security on this web site.

------------------------------------------------

Time to setup a local repository.

Step 1 Create a local directory to store checked out files.

mkdir /development/localcopy

Step 2 Create a subversion repository.

mkdir /development/repos/

svnadmin create /development/repos/svn

Step 3 Check out (nothing) to localcopy

cd /development/localcopy

svn co file:///development/repos/svn/

Check to see that you have a .svn file in /development/localcopy (then you are home free)

Ok so far what do we got.

We have one local repository (shall be synked) and one place to put our checked out files.

------------------------------------------------------------------------------

Time to connect local repository with remote

Let us now sync our local repository with the remote repository. Let us assume our remote repository is https://svn.foo.bar.com/svn. Let us assume that there is a user svnuser and a password there svnpwd.

Do like this. Edit this file

vi /development/repos/svn/hooks/pre-revprop-change.tmpl and make it look like this;

USER="$3"

if [ "$USER" = "svnuser" ]; then exit 0; fi
echo "Only the svnsync user can change revprops" >&2
exit 1

and save it as /development/repos/svn/hooks/pre-revprop-change (that is without file ending)

Go to the repository.

cd /development/repos/svn

svnsync init --username svnuser file:///development/repos/svn/ https://svn.foo.bar.com/svn

This will set up the sync of your local repository.

And now sync;

svnsync sync file:///development/repos/svn/

This might take a while, but in the end your repository will be synchronized.

Time to connect svnweb with local repository

Edit this websvn file.

vi /usr/share/websvn/include/config.php

Add this line.

$config->addRepository('NameToDisplay', 'file:///development/repos/svn');

Crontab job

How do we make svnsync do it regulary, well a crontab job. Let's do it every 30 minutes.

Create script to call from crontab and save it as sync.sh in /development/repository

#!/bin/sh
cd /development/repository
svnsync sync file:///development/repository/svn

chmod file to 755

Do this

crontab -e

add line

*/5 * * * * /development/repository/sync.sh

Add basic auth to apache2

2011-12-14T00:39:00.000-08:00

Here is an extremely short how to allow basic auth to an apache2 web server.

The prerequisites are (in my case):

Ubuntu 9.10

Apache2

Step 1: Install appropriate packages.

apt-get install subversion

apt-get install websvn (this will be stored in /usr/share/websvn)

Step 2: Add basic auth to apache2 configuration

Edit vi /etc/apache2/sites-available/default

Options Indexes Includes FollowSymLinks MultiViews
AllowOverride AuthConfig
Order allow,deny

Allow from all

Step 3: Create a directory ouside of apache2 for password file

mkdir /dev/secure

Step 4: Add a new user (for basic auth)

htpasswd -c /dev/secure/password testuser

Step 5) Create a test directory in the webserver such as /var/www/test

Step 6) Add a .htaccess file there
Add this content to that file

AuthType Basic
AuthName "Restricted Access"
AuthUserFile /dev/secure/password
Require user testuser

Step 7) Add a simple index.html file in the directory
Add content to index.html

hola

Step 8) Restart apache2 /etc/init.d/apache2 restart

That's it

If you browse to localhost/test you shall be promted to enter user testuser and the password you used when creating the password file in step 4

RestService

2011-12-02T04:47:00.000-08:00

Add jersey libs in WEB-INF/lib directory

web.xml

org.aja

Jersey REST Service

com.sun.jersey.spi.container.servlet.ServletContainer

com.sun.jersey.config.property.packages

org.aja

Jersey REST Service

/rest/*

Java classes:

package org.aja;

import javax.ws.rs.GET;

import javax.ws.rs.Path;

import javax.ws.rs.Produces;

import javax.ws.rs.core.MediaType;

@Path("/hello")

public class Hello {

// This method is called if TEXT_PLAIN is request

@GET

@Produces(MediaType.TEXT_PLAIN)

public String sayPlainTextHello() {

return "Hello Jersey";

}

// This method is called if XML is request

@GET

@Produces(MediaType.TEXT_XML)

public String sayXMLHello() {

return "" + " Hello Jersey" + "";

}

// This method is called if HTML is request

@GET

@Produces(MediaType.TEXT_HTML)

public String sayHtmlHello() {

return " " + "" + "Hello Jersey" + ""

+ "

" + "Hello Jersey" + "

" + " ";

}

// This method is called if HTML is request

@GET

@Produces(MediaType.APPLICATION_JSON)

public String sayJsonHello() {

return " " + "" + "Hello Jersey" + ""

+ "

" + "Hello Jersey" + "

" + " ";

}

Java classes:

package org.aja;

import javax.ws.rs.GET;

import javax.ws.rs.Path;

import javax.ws.rs.Produces;

import javax.ws.rs.core.MediaType;

import org.aja.model.Todo;

@Path("/todo")

public class TodoResource {

// This method is called if XMLis request

@GET

@Produces( { MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })

public Todo getXML() {

Todo todo = new Todo();

todo.setSummary("This is my first todo");

todo.setDescription("This is my first todo");

return todo;

}

// This can be used to test the integration with the browser

@GET

@Produces( { MediaType.TEXT_XML })

public Todo getHTML() {

Todo todo = new Todo();

todo.setSummary("This is my first todo");

todo.setDescription("This is my first todo");

return todo;

}

*************

package org.aja.model;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement

// JAX-RS supports an automatic mapping from JAXB annotated class to XML and JSON

// Isn't that cool?

public class Todo {

private String summary;

private String description;

public String getSummary() {

return summary;

}

public void setSummary(String summary) {

this.summary = summary;

}

public String getDescription() {

return description;

}

public void setDescription(String description) {

this.description = description;

}

*********************

package org.aja;

import java.net.URI;

import javax.ws.rs.core.MediaType;

import javax.ws.rs.core.UriBuilder;

import com.sun.jersey.api.client.Client;

import com.sun.jersey.api.client.ClientResponse;

import com.sun.jersey.api.client.WebResource;

import com.sun.jersey.api.client.config.ClientConfig;

import com.sun.jersey.api.client.config.DefaultClientConfig;

public class TestClient {

public static void main(String[] args) {

ClientConfig config = new DefaultClientConfig();

Client client = Client.create(config);

WebResource service = client.resource(getBaseURI());

// Fluent interfaces