JOBS4TIMES

Java Naming and Directory Interface (JNDI)

1. Introduction

Introduction :

• JNDI API is used to communicate with directory server.
• Similar to the Database server, directory server is used to store the data.
• As part of the directory server the data will be store in the form of objects.
• We can choose directory server if insertion operations are very less and select operations are more number of times.
• We can store the data into database fast reader than database server.
• As part of directory server we can store very small amount of data.
• The SQL queries can not be applied of directory server.
• As a java programmer we can write a java application which can talks to directory server.
• If a java program need to talk directory server we have to use JNDI API.
• A java application which uses JNDI API can communicate with directory server.

1. LDAP LightWeight Directory Access Protocol (open source)
2. ADS Active Directory Server from Microsoft
3. NDS Novel Directory Server from Novel

• Our java application which uses JNDI Api can communicate with any directory server.
• Generally directory servers are part of J2EE servers.If we buy the J2EE servers we get the directory servers.

1. Weblogic
2. Websphere
3. JBoss
4. Resin

• LDAP directory server is applied with Weblogic server.
• If we start a Weblogic server by default the directory server will be started.

Procedure to configure Weblogic 10.3 version (pure java s/w) :

The above steps will create a folder with name myDomain in user_projects.
http://localhost:7001/console/

Once if a configure the WebLogic server to start the Weblogic server we need we need to double click on startweblogic.cmd or startweblogic.sh

To access the Weblogic server perform the following steps :

1. Open the Internet Explorer (any browser)
2. Go to the URL and type the url http://localhost:7001/console/
   provide userName, password
   
   Environment --> server --> Admin Server --> view JNDI Tree
3. All the classes and interfaces of JNDI API are available as part of javax.naming package
4. The most important interface of JNDI is Context
5. The most important class name is InitialContext
6. In case of weblogic server LDAP directory server integrated with our server.
7. If we start the weblogic server internally its going to start the directory server also.
8. We can develop java application which interacts with directory server.
9. Weblogic people as provided the implementation of JNDI API , this implementation is called as JNDI driver
10. The JNDI driver is available with weblogic server in the form of jar files
    weblogic 8.1 ---> weblogic.jar
    weblogic 8.3 ---> wlclient.jar
    (bea/wlserver 10.3/server/lib)

Develop JNDI application which can get the InitialContext object :

package com.jndi;

import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class JndiDemo {
public static void main(String args[]) throws NamingException{

Hashtable h=new Hashtable();
h.put(Context.INITIAL_CONTEXT_FACTORY,
        "weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, "t3://localhost:7001");
h.put(Context.SECURITY_CREDENTIALS, "weblogic");
h.put(Context.SECURITY_PRINCIPAL, "weblogic");
		
InitialContext ic=new InitialContext(h);
System.out.println("Object is : "+ ic);
}
}

Procedure to develop java application which interacts with the directory server :

• To establish connection with directory server, we need the JNDI driver class name , which provide the implementation of Context interface, url, user name of weblogic server and password of weblogic server.
• We need to place all these details inside a Hashtable object.
• We need to supply the Hashtable object has input to InitialContext constructor.

Admin server

1. Create object - bind() method
2. Remove object - unbind() method
3. Update object - rebind() method
4. Retrieve object - lookup() method

We have to use the following key in the Hashtable :

Develop a JNDI application which add a name object to the directory server :

package com.jndi;

import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class JndiCreateObject {
public static void main(String args[]) throws NamingException{

Hashtable h=new Hashtable();
h.put(Context.INITIAL_CONTEXT_FACTORY,
		"weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, "t3://localhost:7001");
h.put(Context.SECURITY_CREDENTIALS, "weblogic");
h.put(Context.SECURITY_PRINCIPAL, "weblogic");
		
InitialContext ic=new InitialContext(h);

String name="Ashok JavaProgrammer";
ic.bind("same", name);
System.out.println("object is added to directory server");

}
}

Develop a JNDI application which adds an ArrayList object to Directory server :

package com.jndi;

import java.util.ArrayList;
import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class JndiAddEmpObject {
public static void main(String args[]) throws NamingException{

Hashtable h=new Hashtable();
h.put(Context.INITIAL_CONTEXT_FACTORY,
		"weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, "t3://localhost:7001");
h.put(Context.SECURITY_CREDENTIALS, "weblogic");
h.put(Context.SECURITY_PRINCIPAL, "weblogic");
		
InitialContext ic=new InitialContext(h);

ArrayList  a=new ArrayList();
a.add("EmpOne");
a.add("EmpTwo");

ic.bind("emplist", a);
System.out.println("object is added to directory server");

}
}

• When we use the bind() method it adds the object to the directory server.
• The bind() method converts the object into super class reference object.

String name="Sai Java";
Object o=name;

ArrayList a = new ArrayList();
Object o=a;

Develop a JNDI application which delete an object stored in Directory server :

package com.jndi;

import java.util.ArrayList;
import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class JndiDeleteObject {
public static void main(String args[]) throws NamingException{

Hashtable h=new Hashtable();
h.put(Context.INITIAL_CONTEXT_FACTORY,
		"weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, "t3://localhost:7001");
h.put(Context.SECURITY_CREDENTIALS, "weblogic");
h.put(Context.SECURITY_PRINCIPAL, "weblogic");
		
InitialContext ic=new InitialContext(h);
ic.unbind("sname");
System.out.println("object is removed from directory server");

}
}

Develop a JNDI application, update an object stored in Directory server :

package com.jndi;

import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class JndiUpdateObject {
public static void main(String args[]) throws NamingException{

Hashtable h=new Hashtable();
h.put(Context.INITIAL_CONTEXT_FACTORY,
		"weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, "t3://localhost:7001");
h.put(Context.SECURITY_CREDENTIALS, "weblogic");
h.put(Context.SECURITY_PRINCIPAL, "weblogic");
		
Context ic=new InitialContext(h);
ic.rebind("sname", "Student name modified");
System.out.println("object is updated in directory server");

}
}

Develop a JNDI application which retrieves an object stored in Directory server :

package com.jndi;

import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class JndiRetrieveObject {
public static void main(String args[]) throws NamingException{

Hashtable h=new Hashtable();
h.put(Context.INITIAL_CONTEXT_FACTORY,
		"weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, "t3://localhost:7001");
h.put(Context.SECURITY_CREDENTIALS, "weblogic");
h.put(Context.SECURITY_PRINCIPAL, "weblogic");
		
Context ic=new InitialContext(h);
Object o=ic.lookup("sname");
String s=(String)o;
System.out.println("object is retrieved : " + s );

}
}

• When we add an object to the directory server the object will added to InitialContext directly.
• If we want to place all the related objects in one group then create a subcontext.

ic.createSubcontext("Student");
ic.createSubcontext("Student.MCA");
ic.destroySubcontext("Student");

Connection Pool Technique :

• Without this technique will not develop any projects.
• Every DB Administrator will configure , how many max number of connections can be given by DB server.
• When the Administrator configure that it store inside a file
  oracle --> config --> init.ora // open with notepad
• Every database server will having limits and issue the connections to the applications.
• Connection pool is a java program, which can maintain set of connections with him, The connection pool program aquires the connection from the DB and holds those connections.

Procedure to configure the connections through in the Weblogic server :

• In the Weblogic server perform all the above steps , it creates the connection pool in initial capacity as 1.
• To modified capacity go to services and goto DataSources option, and click on DataSourceName then goto connection pool tab and modified it.

Start --> Oracle 10g --> goto DB Home page --> Administration --> Monitor --> sessions

Weblogic --> services --> JDBC --> Data Sources --> new

Procedure to get a connection from Connection Pool :

• Write the JNDI code to get DataSource object from directory server.
• From the DataSource object get the connection.
  Note : If we try to get the connection object from DataSource , that object is type logical.

1. We can get the connection from Weblogic server.
2. create the Statement object.
3. Execute the Query.
4. Close the connection.

DataSource interface is part of javax.sql package.

package com.jndi;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;

public class DBConnect {
public static void main(String args[]) 
             throws NamingException, SQLException{

Hashtable h=new Hashtable();
h.put(Context.INITIAL_CONTEXT_FACTORY,
		"weblogic.jndi.WLInitialContextFactory");
h.put(Context.PROVIDER_URL, "t3://localhost:7001");
h.put(Context.SECURITY_CREDENTIALS, "weblogic");
h.put(Context.SECURITY_PRINCIPAL, "weblogic");
		
Context ic=new InitialContext(h);
Object o=ic.lookup("myPool");
DataSource ds=(DataSource)o;
Connection con=ds.getConnection();
Statement stmt=con.createStatement();
ResultSet rs=stmt.executeQuery("select * from product");

while(rs.next()){
System.out.println(rs.getString(1));
System.out.println(rs.getString(2));
}

}
}

• To run above connection pool object, we have create a command setDomainEnv.cmd , this file is available inside bin directory at our domain (myDomain/bin)
• In connection pool program, if we write the code to close the connections using con.close() , then connection will be return back to the Connection pool.