import javax.naming.*;
import javax.naming.directory.*;

import java.util.Hashtable;

/**
 * Demonstrates how to enable connection pooling. Use debug option
 * to observe connection usage.
 *
 * usage: java -Dcom.sun.jndi.ldap.connect.pool.debug=fine UsePool
 */
class UsePool {
    public static void main(String[] args) {
	// Set up environment for creating initial context
	Hashtable env = new Hashtable(11);
	env.put(Context.INITIAL_CONTEXT_FACTORY, 
	    "com.sun.jndi.ldap.LdapCtxFactory");
	env.put(Context.PROVIDER_URL, "ldap://localhost:389/o=JNDITutorial");

	// Enable connection pooling
	env.put("com.sun.jndi.ldap.connect.pool", "true");

	try {
	    // Create one initial context (Get connection from pool)
	    DirContext ctx = new InitialDirContext(env);

	    System.out.println(ctx.getAttributes("ou=NewHires"));

	    // do something useful with ctx

	    // Close the context when we're done
	    ctx.close();   // Return connection to pool

	    // Create another initial context (Get connection from pool)
	    DirContext ctx2 = new InitialDirContext(env);

	    System.out.println(ctx2.getAttributes("ou=People"));

	    // do something useful with ctx2

	    // Close the context when we're done
	    ctx2.close();   // Return connection to pool

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

This same property is also used to specify a timeout period for establishment of the LDAP connection, as described in the Connection Creation section.

When Not to Use Pooling

Connection Pooling Configuration