Example Code: EJB

Bean Inheritance Example

README

Overview
========

This example show two beans: Foo and Bar. In the example, the Bar bean
inherits from the Foo bean. The required coding and the effects of
this bean inheritance are demonstrated in this example.


Source Files
============


Client.java
-----------

You invoke the client program from a command prompt, and pass it four
arguments, the

   - service URL (service ID, hostname, port, and SID if port is a listener)
   - name of the published bean to lookup and instantiate
   - username
   - password that authenticates the client to the Oracle8i database server

For example:
% java -classpath LIBs Client sess_iiop://localhost:2222 /test/myHello scott 
tiger

where LIBs is the classpath that must include

$ORACLE_HOME/lib/aurora_client.jar
#If using Java 2, use classes12.zip instead of classes111.zip
$ORACLE_HOME/jdbc/lib/classes111.zip
$ORACLE_HOME/lib/vbjorb.jar
$ORACLE_HOME/lib/vbjapp.jar
$JAVA_HOME/lib/classes.zip

(Note: for NT users, the environment variables would be %ORACLE_HOME% and
%JAVA_HOME%.)

The client code performs the following steps:

   - gets the arguments passed on the command line
   - creates a new JNDI Context (InitialContext())
   - looks up the published bean to find and activate its home interface
   - using the home interface, instantiates through its create()
     method a new bean object, hello
   - invokes the helloWorld() method on the hello object and prints the results

The printed output is:

Hello World
Hello World from bar
Hello World 2 from bar
Hello World from bar


foo.ejb
-------

The Foo bean deployment descriptor. See ../helloworld/readme.txt for a
more complete description of a typical example deployment descriptor.


bar.ejb
-------

The bar bean deployment descriptor.


inheritance/FooHome.java
------------------------

The Foo bean home interface. Specifies a single no-parameter create() method.


inheritance/Foo.java
--------------------

The Foo remote interface. Note that only a single method, hello(), is
specified.


inheritance/BarHome.java
------------------------

The Bar bean home interface. Specifies a single no-parameter create() method.


inheritance/Bar.java
--------------------

The Bar remote interface. Note that only a single method, hello2(), is
specified.


inheritanceServer/FooBean.java
------------------------------

The Foo bean implementation. Implements the hello() method of
inheritance/Foo.java, returning a String greeting.


inheritanceServer/BarBean.java
------------------------------

The Bar bean implementation. Implements both the hello() method inherited from
FooBean, as well as the hello2() method specified in inheritance/Bar.java.

Note that this bean extends FooBean, so it does not implement SessionBean or
any of its methods, such as ejbRemove(0, ejbActivate(), and so on, which is
normally a requirement of a session bean. This is because BarBeam inherits the
implementation of these from FooBean.


Compiling and Running the Example
=================================


UNIX
----

Enter the command 'make all' or simply 'make' in the shell to compile,
load, and deploy the objects, and run the client program.  Other
targets are 'run' and 'clean'.

Make sure that a shell environment variable ORACLE_HOME is set to
point to the home location of the Oracle installation. This is
operating system dependent, so see the Installation documentation that
came with your system for the location. Also, review the README file
for the Oracle database, and the README file for the CORBA/EJB server
(the Oracle8i ORB), for additional up-to-date information.


Windows NT
----------

On Windows NT, run the batch file makeit.bat from a DOS command prompt
to compile, load, and deploy the objects. Run the batch file runit.bat
to run the client program, and see the results.


Make sure that the environment variables %ORACLE_HOME%, %CLASSPATH%,
and %SERVICE% are set appropriately for the DOS command window. You
can set these as either user or system environment variables from the
Control Panel. Double click on System in the Control Panel then on
the Environment tab to set these variables. Start a new DOS window
after setting environment variable values.


See the Installation documentation that came with your Oracle8i system
for the values of these variables. Also, review the README file for
the Oracle database, and the README file for the CORBA/EJB server (the
Oracle8i ORB), for additional up-to-date information.

You can also set an environment variable %JAVA_HOME% to point to the
root of your Java JDK. For example, SET JAVA_HOME=C:\JDK1.1.6.

Client

import inheritanceServer.*;
import inheritance.*;

import oracle.aurora.jndi.sess_iiop.ServiceCtx;

import javax.naming.Context;
import javax.naming.InitialContext;
import java.util.Hashtable;

public class Client
{
  public static void main(String[] args) throws Exception {
    if (args.length != 5) {
      System.out.println("usage: Client serviceURL fooBeanName "
			  + "barBeanName username password");
      System.exit(1);
    }

    String serviceURL = args [0];
    String fooBeanName = args [1];
    String barBeanName = args[2];
    String username = args[3];
    String password = args[4];

    Hashtable env = new Hashtable();
    env.put(Context.URL_PKG_PREFIXES, "oracle.aurora.jndi");
    env.put(Context.SECURITY_PRINCIPAL, username);
    env.put(Context.SECURITY_CREDENTIALS, password);
    env.put(Context.SECURITY_AUTHENTICATION, ServiceCtx.NON_SSL_LOGIN);
    Context ic = new InitialContext(env);


    // Get a foo object from a foo published bean
    FooHome home = (FooHome) ic.lookup(serviceURL + fooBeanName);
    Foo foo = home.create();
    System.out.println(foo.hello());

    // Get a bar object from a bar published bean
    BarHome barHome = (BarHome) ic.lookup(serviceURL + barBeanName);
    Bar bar = barHome.create();
    System.out.println(bar.hello());
    System.out.println(bar.hello2());


    // Get a foo object from a bar published bean
    BarHome fooBarHome = (BarHome)ic.lookup(serviceURL + barBeanName);
    Foo fooBar = (Foo) fooBarHome.create();
    System.out.println(fooBar.hello());
  }
}

Home Interface

BarHome.java

package inheritance;

import javax.ejb.EJBHome;
import javax.ejb.CreateException;
import java.rmi.RemoteException;

public interface FooHome extends EJBHome
{
  public Foo create () throws RemoteException, CreateException;
}

FooHome.java

package inheritance;

import javax.ejb.EJBHome;
import javax.ejb.CreateException;
import java.rmi.RemoteException;

public interface FooHome extends EJBHome
{
  public Foo create () throws RemoteException, CreateException;
}

Remote Interface

Bar.java

package inheritance;

import javax.ejb.EJBObject;
import java.rmi.RemoteException;

public interface Foo extends EJBObject  
{
  public String hello () throws RemoteException;
}

Foo.java

package inheritance;

import javax.ejb.EJBObject;
import java.rmi.RemoteException;

public interface Foo extends EJBObject  
{
  public String hello () throws RemoteException;
}

Bean Implementation

BarBean.java

package inheritanceServer;

import java.rmi.RemoteException;
import javax.ejb.*;
import oracle.aurora.jndi.sess_iiop.*;

public class FooBean implements SessionBean
{
  // Methods of the interface
  public String hello () throws RemoteException {
    return "Hello World";
  }

  // Methods of the SessionBean
  public void ejbCreate () throws RemoteException, CreateException {
  }

  public void ejbRemove() {
  }

  public void setSessionContext (SessionContext ctx) {
  }

  public void ejbActivate () {
  }

  public void ejbPassivate () {
  }
}

FooBean.java

package inheritanceServer;

import java.rmi.RemoteException;
import javax.ejb.*;
import oracle.aurora.jndi.sess_iiop.*;

public class FooBean implements SessionBean
{
  // Methods of the interface
  public String hello () throws RemoteException {
    return "Hello World";
  }

  // Methods of the SessionBean
  public void ejbCreate () throws RemoteException, CreateException {
  }

  public void ejbRemove() {
  }

  public void setSessionContext (SessionContext ctx) {
  }

  public void ejbActivate () {
  }

  public void ejbPassivate () {
  }
}