Dependency INjection through Annotations

[amarshi mohanty]

Hi All,

I have an EJB Module project which has:

package com.stateless;
public interface HelloWorldInf {
	
	public String getMessage(String msgFromClient);
	
}

package com.stateless;

import javax.ejb.Local;
import javax.ejb.Stateless;

@Stateless
@Local
public class DepInjBean implements HelloWorldInf{
	
	
	@Override
	public String getMessage(String msgFromClient) {
		 return "Hi " + msgFromClient;
	}
		
}

And below is the web module:

package com.stateless;

import java.util.Hashtable;
import javax.ejb.EJB;
import javax.naming.Context;

public class DepInjHelloWorld {

	/**
	 * @param args
	 */
	@EJB public static HelloWorldInf hello;
	public static void main(String[] args) {
		Hashtable <String,String> env = new Hashtable<String, String>();
		env.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory");
		env.put(Context.PROVIDER_URL,"jnp://localhost:1099");
		try{	
				System.out.println("Starting...");
	            System.out.println(hello.getMessage("Using Annotations Instead Of JNDI LookUp"));
		}catch (Exception e) {
			e.printStackTrace();
		}

	}

}

But i am getting the bewlo exception:
Starting...
java.lang.NullPointerException
at com.stateless.DepInjHelloWorld.main(DepInjHelloWorld.java:19)


Line 19:System.out.println(hello.getMessage("Using Annotations Instead Of JNDI LookUp"));

PLease tell me if i need to configure anywhere,as i am not using any xml file.

Regards,
Amarshi

[Jeanne Boyarsky]

That's not a web module; it is a main method. Are you running it as an application client or a regular Java class? If the later, you need to do a JNDI lookup and not dependency injection.

[amarshi mohanty]

I have also tried using a servlet instead of the standalone class, but the same exception comes.


---Amarshi

[pulkit mehra]

Hi Amrish,

Hope this help
This is Stand Alone Client for EJB 3.0 in JBoss :

public static void main(String args[]){
        try {
            Context jndiContext = getInitialContext( );
            Object ref = jndiContext.lookup("MyServiceContextBean/remote");
            MyServiceContext bean = (MyServiceContext)
                    PortableRemoteObject.narrow(ref,MyServiceContext.class);

            bean.callMethod();
        } catch (javax.naming.NamingException ne)
            {
               ne.printStackTrace( );
            }

    }

    public static Context getInitialContext( )
            throws javax.naming.NamingException {

        Properties p = new Properties( );
        p.put(Context.SECURITY_PRINCIPAL, "guest");
        p.put(Context.SECURITY_CREDENTIALS, "guest");
        p.put(Context.INITIAL_CONTEXT_FACTORY,
                "org.jnp.interfaces.NamingContextFactory");
        p.put(Context.URL_PKG_PREFIXES,
                " org.jboss.naming:org.jnp.interfaces");
        p.put(Context.PROVIDER_URL, "jnp://localhost:1099");
        return new javax.naming.InitialContext(p);
    }

[amarshi mohanty]

Thanks pulkit, i have tried this way its working.
But i want to use dependency injection instead of jndi lookup.
I have googled a couple of examples (using dependency injection for jndi look up instead of using initial context for lookup), but for me the business interface instance comes as null.

[Jaikiran Pai]

You actually have 2 questions here.

1) Injection into standalone java clients - This isn't possible unless you use an application client container. See this previous discussion

2) Injection into servlets - This is allowed. If you are not able to inject into servlet, then see if the issue is related to this

[pulkit mehra]

See..according to my experience dependency injection gets failed due to following reason :

1)You are using server which does not support DI in web container.eg JBoss 4.x(DI work in EJB not in WEB)
2)You must have giving wrong JNDI name.Please refer to JNDI console of your server and see naming convention they follow.