JavaEE6 Weblogic exercice 2

Introduction

This time we will look at new features of Java EE6/JPA:
 

1. Build an Enterprise project, not a "web profile project",
2. Write an remote EJB and test a standalone remote client (not a Servlet),
3. Write a bank account management web application that will generate and update the database schema as we update the code of the entity classes,
4. Use JPA relationships

Create an EAR project, an EJB project and a Dynamic Web/JPA project

An Enterprise Application project (EAR) is a "composite" project, a container that will hold several other projects and deploy all of them at once in a .ear archive.

Typically, an EAR project will be attached with several other subprojects such as:

• EJB projects,
• Dynamic web projects (maybe with JPA facets),

1. So, let's do it. Create a new project of type "enterprise application project" called DemoEAR. For the moment, do not set anything, just click finish. We create this project first as when we will create the subprojects, we will speficy that they belong to this EAR project.
2. Create an EJB project, call it "DemoEJB", indicate under "EAR Membership" that you want to attach it to the EAR project from step 1, notice that a DemoEJBClient project is automatically added too. More on that later.
3.  Add a JPA facet to the EJB project you just created, 
4. Create a Dynamic Web project,  name it "DemoWeb", indicate  under "EAR Membership"  that you want to attach it to the EAR project from step 1, click next until the last screen and check "generate web.xml",

So, you should get 4 projects: DemoEAR, demoEJB, demoEJBClient and demoWeb. You can check that everything is ok by looking at the properties of the DemoEAR projec, then look at "Deployment Assembly", you should see that the 3 other projects are in the assembly.

Add a remote EJB to the dynamic web project

Add a session bean stateless but this tome check the "remote interface" option, and indicate for the name of the bean " DemoSessionEJB" and for the remote interface you should see that the dialog proposes automatically DemoSessionEJBRemote. Add an hello world method to the bean, like we did at the beginning of exercice one, yesterday.

The code should look like that: 

package sessions;

import javax.ejb.LocalBean;
import javax.ejb.Stateless;

/**
 * Session Bean implementation class DemoSessionEJB
 */
@Stateless
@LocalBean
public class DemoSessionEJB implements DemoSessionEJBRemote {

    public String helloWorld() {
    	return "hello world !";
    }
}

Notice that the bean implements DemoSessionEJBRemote , and that this interface has been automatically added to the DemoEJBClient project. This "generated project" is useful for standalone clients, as we will see now...

Add the helloWord() method to the remote interface, in the file DemoSessionEJBRemote.java, from the DemoEJBClient project. The code should look like that:

package sessions;

import javax.ejb.Remote;

@Remote
public interface DemoSessionEJBRemote {
	 public String helloWorld();
}

At this stage, save all and deploy the EAR project to weblogic using right click on the server in the server tab of the Java EE perspective, and use the add/remote menu.

It is important to deploy this project as we will need the JNDI name of the EJB we created, and this JNDI name is available from the weblogic admin console.

Look for the JNDI name of the EJB in Weblogic console

 You can do that by looking at the weblogic admin console, on the left, click on "base_domain", then "servers", then in the main page click on the name of your server, then in the main window you should have something like "JNDI tree"... Click on that, a new tab opens in which you can explore the names objects on your server. In the small tree, click on "weblogic" then you will find your application and the EJBs deployed. The "liaison name" of the EJB is the JNDI name. It should look like this: " java:global.DemoEAR.DemoEJB.DemoSessionEJB!sessions.DemoSessionEJBRemote "

We will use this JNDI identifier in the standalone client... 

Write a standalone client for this EJB

A standalone client is just a Java project with a java class (with a main) that uses the remote EJB we created. 

The client project is just a Java project. Create a new project of type "Java project", name it "DemoEJBClientStandalone".   

You must add two things in the build path so that the client code can compile and run:

1. Add the DemoEJBClient project in the build path (the project that contains the EJB remote interface you are going to call),
2. Add wlfullclient.jar, a jar with all the client libs you need. This jar needs to be built once, using a command line interface. This is the procedure to build this jar: cd in the WEBLOGIC_INSTALL_LIB/server/lib, then run the command "java -jar wljarbuilder.jar". This will take 30s to build the client lib for your installation. At the end, you should find a wlfullclient.jar file. Add it to your build path.
3. Add a new java class with a main(), name it  StandAloneClient, 
4. Copy this source code provided below, check that the  JNDI_NAME is the same as the one you saw in the weblogic admin console/jndi tree. 

Then you should have such a source code for the standalone client:
 

package client;

import java.util.Hashtable;import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import sessions.TestRemote;

public class StandAloneClient {
    private static String INITIAL_CONTEXT_NAME = "weblogic.jndi.WLInitialContextFactory";
    private static String PROVIDER_URL = "t3://localhost:7001";
    private static String JNDI_NAME = "java:global.DemoEAR.DemoEJB.DemoSessionEJB!sessions.DemoSessionEJBRemote";

    public static void main(String[] args) throws Exception {
        Context ctx = getInitialContext();
        TestRemote helloEJB = (TestRemote) ctx.lookup(JNDI_NAME);
        System.out.println(helloEJB.helloWorld());
        }

    private static Context getInitialContext() throws NamingException {
        Hashtable env = new Hashtable();
        env.put(Context.INITIAL_CONTEXT_FACTORY, INITIAL_CONTEXT_NAME);
        env.put(Context.PROVIDER_URL, PROVIDER_URL);
        return new InitialContext(env);
    }
}

These info come from the Weblogic documentation (name of INITIAL_CONTEXT_FACTORY, etc.)

Redeploy the EAR project, just to be sure (right click on server, then "add and remove").

Run the standalone client project (as a "Java application").

Normally you should see in the console the "Hello World" message. As you saw, we could call the EJB from any external host, as long as we indicate the right URL for the weblogic server.

Write a bank account management application

This time, we will write a real application. A small bank account manager.

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
int id;

package entities;

import java.io.Serializable;
import javax.persistence.*;

/**
 * Entity implementation class for Entity: Account
 *
 */
@Entity
public class Account implements Serializable {
	private static final long serialVersionUID = 1L;
	
	@Id
	@GeneratedValue(strategy=GenerationType.AUTO)
	int id;
	String name;
	int balance;

	public Account() {
	}
	
	public Account(String name, int balance) {
		this.name = name;
		this.balance = balance;
	}
	
	public void add(int ammount) {
		balance += ammount;
	}
	
	public void remove(int ammount) {
		balance -= ammount;
	}
	
	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 int getBalance() {
		return balance;
	}

	public void setBalance(int balance) {
		this.balance = balance;
	}	
}

 public Account create(String name, int balance) {
    Account a = new Account(name, balance);
    // insert in database
    em.persist(a);
    return a;
}

public void createTestData() {
    create("John Lennon", 150000);  
    create("Paul Mac Cartney", 950000);  
    create("Ringo Starr", 20000);  
    create("Georges Harrisson", 100000); 
}

package entities;

import javax.annotation.PostConstruct;
import javax.ejb.EJB;
import javax.ejb.LocalBean;
import javax.ejb.Singleton;
import javax.ejb.Startup;

import sessions.AccountFacade;

/**
 * Session Bean implementation class InitEJB
 */
@Startup
@Singleton
@LocalBean
public class InitEJB {
	@EJB
	AccountFacade facade;

	@PostConstruct
    public void init() {
        System.out.println("### Initialization of the database, adding some test accounts ###");
    }
}