JNDI Naming Service Example

In the previous chapter we discussed the very basics of JNDI. In this chapter we are going to discuss a JNDI example .In this chapter we are looking into the JNDI naming service interface .

JNDI Naming Service Example

This example shows how an object can be bound to a name. And how to access the bound object using another application.

JBossNS- Overview

The example we are discussing is with JBoss server. JBoss is having its own JNDI naming implementation-JBossNS. JBossNS is the Socket/RMI implementation of javax.naming.Context interface.If we bound an object and if we try to access the same from the same machine, then socket is not creating. In such case , global singleton object reference is using.If we are accessing the object from another machine , the sockets would be created between two machines.In such situation , the the class whose object is bound , should implement the Serializable interface.In such scenario, the serialVersionUID attribute should be same at both sides.This concept is explained in a previous chapter.

Lets start our discussion from the very basics of setting up the environment.Java EE can be downloaded from here. Eclipse Indigo is using as IDE. It can be downloaded from here .Now we need to have JBoss application server. I am going to use JBoss version 4.2. We can download it from here.

Step 1. Open eclipse in any workspace . And create a dynamic web project with JBoss 4.2.0 GA as target run time.

2.Create a new JBoss instance and add our newly created project to the server.

3.Create package com.jndi.samples in src directory.

4.Now create the following classes.

In this example , first application binding a Student object. The second application retrieves the bound object.

Student.java

import java.io.Serializable;


public class Student implements Serializable {
    public Student(int id, String name) {

        this.id = id;

        this.name = name;

    }
    private static final long serialVersionUID = 1L;
    private int id;

    private String name;
    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 toString(){

        return "Id = "+getId() +"Name = "+getName();

    }

}

Now let us see how to bind a student object using naming service. The FirstApp.java is a stand alone application which binds a Student object.

FirstApp.Java

import java.util.Properties; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException;


public class FirstApp {

    public void bindObject() {

        Student student = new Student(1, "Bijoy");

        Properties initialProperties = new Properties();

        initialProperties.put(InitialContext.INITIAL_CONTEXT_FACTORY,

                "org.jnp.interfaces.NamingContextFactory");

        initialProperties.put(InitialContext.PROVIDER_URL,

                "jnp://localhost:1099");

        initialProperties.put(InitialContext.URL_PKG_PREFIXES,

                "org.jboss.naming:org.jnp.interfaces");

        try {

            Context context = new InitialContext(initialProperties);

            context.bind("student", student);

            System.out.println("Bound object = "+student);

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

        }
    }

public static void main(String[] args) { new FirstApp().bindObject(); } }

The bindObject() method creates a Context object and a Student object is binding to the specified context . The initialProperties has the details for initializing the context.It is desirable to give these properties through jndi.properties in src folder , if we need these things in a generic way.

Now lets see the SecondApp.java. It simply receovers the already bound Student object.

SecondApp.java

import java.util.Properties; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException;


public class SecondApp {

    public void readObject() {

        Properties initialProperties = new Properties();

        initialProperties.put(InitialContext.INITIAL_CONTEXT_FACTORY,

                "org.jnp.interfaces.NamingContextFactory");

        initialProperties.put(InitialContext.PROVIDER_URL,

                "jnp://localhost:1099");

        initialProperties.put(InitialContext.URL_PKG_PREFIXES,

                "org.jboss.naming:org.jnp.interfaces");

        try {

            Context context = new InitialContext(initialProperties);

            Student student = (Student) context.lookup("student");

            System.out.println("Object received from context = "+student);

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

        }
    }
    public static void main(String[] args) {

        new SecondApp().readObject();