InitialContext lookup

[L Goundalkar]

Hi,
I have some basic clarifications.
1. What exactly happens when I say new InitialContext.lookup("mybean");
2. How can i look up a EJB residing in different machine from a web component.
3. What do you mean by java:comp\env ??
4. How does my JVM know about the JNDI server? Do we need to specify the IP address and other details of JNDI server while looking up for home object?

Thanks for the time.

[Edward Kenworthy]

Basically it's performing a name lookup. It matches the name you give in the lookup method call to a list held by a nameserver and returns a reference to the "thing" it found- in your case I guess an EJB of some kind's home interface.
What's significant about the java/compblahblahblah bit?- not much. It's simply a naming convention to separate java names from any other kind of 'thing' that the name server knows about.

[Vishwa Kumba]

1. What exactly happens when I say new InitialContext.lookup("mybean");
- An Object that is bound to the name "mybean" is returned from the JNDI Server.Usually we use calls like this, to get a reference to the home reference of an EJB, from an EJBClient.
2. How can i look up a EJB residing in different machine from a web component.
- By creating a different InitialContext Object. The InitialContext Object takes Hashtable or Properties Object in the constructor. You will fill in the details like IP Address, Port number etc of the other EJB Server in the Hashtable.
3. What do you mean by java:comp\env ??
- As Edward said, it is bean's own private name space, in which you store constants used by the bean.
4. How does my JVM know about the JNDI server? Do we need to specify the IP address and other details of JNDI server while looking up for home object?
- Yes. While creating the InitialContext, you specify these details including the JNDI Driver.
For example, to retrieve an EJB home reference in an EJBClient program:

  
    Hashtable env = new Hashtable();
    env.put(Context.INITIAL_CONTEXT_FACTORY, 
                  "org.jnp.interfaces.NamingContextFactory");
    env.put(Context.PROVIDER_URL, "172.13.45.67:1099");
    Context ctx = new InitialContext(env);
    Object ref = ctx.lookup("MyFirstBean");
    HelloHome home = (HelloHome) PortableRemoteObject.
                                 narrow(ref, HelloHome.class);
    HelloRemote remote = home.create();

[ March 03, 2004: Message edited by: Vish Kumar ]

[L Goundalkar]

Thanks edward and vish.

[Manoj Raghuwanshi]

I am having a EJB server and client running on different jvm.

Lookup code is-

Hashtable env = new Hashtable();
env.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory");
env.put(Context.PROVIDER_URL, jndiUrl);
env.put("java.naming.factory.url.pkgs", "org.jboss.naming rg.jnp.interfaces");

try
{
InitialContext jndiContext=new InitialContext(env);
Object ref=jndiContext.lookup("PDFHandler");

some code


JndiUrl is->jnp://192.168.0.5:1099

what i am getting is-
javax.naming.CommunicationException [Root exception is java.rmi.NoSuchObjectException: no such object in table]



where I am going wrong?

Thanks
[ March 11, 2005: Message edited by: Manoj Raghuwanshi ]

[arunij katiliyar]

Please check whether the JNDI url string is vaild and points to the jndi server or appserver hosting the JNDI service .

If its valid then check the JNDI name that you used for lookup . Check in the appserver whether the ejb is pinned to this name . I believe its the JNDI url string problem .


Murugan

[Manoj Raghuwanshi]

my problem is not solved please help me

I made some changes in jboss.xml

Earlier version was this:-

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE jboss PUBLIC "-//JBoss//DTD JBOSS 3.0//EN" "http://www.jboss.org/j2ee/dtd/jboss_3_0.dtd">

<jboss>

<unauthenticated-principal>nobody</unauthenticated-principal>

<enterprise-beans>

<session>
<ejb-name>StringProcessorBean</ejb-name>
<jndi-name>StringProcessor</jndi-name>
</session>

</enterprise-beans>

<resource-managers>
</resource-managers>

</jboss>



changes made:-

<ejb-name>StringProcessorBean</ejb-name>
<jndi-name>StringProcessorBean</jndi-name>


setup is same ejb deployed on 192,168.0.5(linux box) and client on
192.168.0.245(linux box)

now I am getting following exception

java.rmi.ConnectException: Connection refused to host: 127.0.0.1

[ March 15, 2005: Message edited by: Manoj Raghuwanshi ]
[ March 15, 2005: Message edited by: Manoj Raghuwanshi ]

[Manoj Raghuwanshi]

ok at last i solved the problem.

change /etc/hosts file

192.168.0.5 gladiator
127.0.0.1 localhost

now it is a distributed application
thanks any way