EJB Application Client Clarification

[Jack Bush]

Hi EJB Guru,

I would like some clarification on accessing Remote/Local Session Bean using an Application Client. In other word, there appears to be more than one approach to the same Session bean. Let's start by declaring the Converter EJB:

package converter.ejb;
 
import java.math.BigDecimal;
import javax.ejb.Remote;
 
@Remote
public interface Converter {
    public BigDecimal dollarToYen(BigDecimal dollars);
 
    public BigDecimal yenToEuro(BigDecimal yen);
}

package converter.ejb;
 
import java.math.BigDecimal;
import javax.ejb.Stateless;
 
@Stateless
public class ConverterBean implements converter.ejb.Converter {
    private BigDecimal euroRate = new BigDecimal("0.0070");
    private BigDecimal yenRate = new BigDecimal("112.58");
 
    public BigDecimal dollarToYen(BigDecimal dollars) {
        BigDecimal result = dollars.multiply(yenRate);
 
        return result.setScale(2, BigDecimal.ROUND_UP);
    }
 
    public BigDecimal yenToEuro(BigDecimal yen) {
        BigDecimal result = yen.multiply(euroRate);
 
        return result.setScale(2, BigDecimal.ROUND_UP);
    }
}

I have two method to accessing this bean.

( i ) Lookup JNDI using the following set of code:

package converter.client;
 
import converter.ejb.Converter;
import java.math.BigDecimal;
import javax.ejb.EJB;
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.naming.NamingException;
 
public class ConverterClient {
    
    public static void main(String[] args) {
 
        try {
            InitialContext ctx = new InitialContext();
            ConverterRemote jndiconverter = (ConverterRemote) ctx.lookup("converter.ejb.ConverterRemote");
 
            BigDecimal param = new BigDecimal("100.00");
            BigDecimal yenAmount = jndiconverter.dollarToYen(param);
 
            System.out.println("$" + param + " is " + yenAmount + " Yen.");
 
            BigDecimal euroAmount = jndiconverter.yenToEuro(yenAmount);
            System.out.println(yenAmount + " Yen is " + euroAmount + " Euro.");
 
            System.exit(0);
        } catch (javax.naming.NamingException ne) {
            System.err.println("Caught an unexpected exception!");
            ex.printStackTrace();
        }
    }
}

( ii ) Application Client lookup?

package converter.client;
 
import converter.ejb.Converter;
import java.math.BigDecimal;
import javax.ejb.EJB;
 
public class ConverterClient {
    @EJB
    private static Converter converter;
 
    /** Creates a new instance of Client */
    public ConverterClient(String[] args) {
    }
 
    public static void main(String[] args) {
        ConverterClient client = new ConverterClient(args);
        client.doConversion();
    }
 
    public void doConversion() {
        try {
            BigDecimal param = new BigDecimal("100.00");
            BigDecimal yenAmount = converter.dollarToYen(param);
 
            System.out.println("$" + param + " is " + yenAmount + " Yen.");
 
            BigDecimal euroAmount = converter.yenToEuro(yenAmount);
            System.out.println(yenAmount + " Yen is " + euroAmount + " Euro.");
 
            System.exit(0);
        } catch (Exception ex) {
            System.err.println("Caught an unexpected exception!");
            ex.printStackTrace();
        }
    }
}

It is the first time I come a cross method ( ii ) and could not get it to work properly. The error message

received were:

SJSAS server side

**RemoteBusinessJndiName: converter.ejb.Converter; remoteBusIntf: converter.ejb.Converter
LDR5010: All ejb(s) of [converter] loaded successfully!
Registering ad hoc servlet: WebPathPath: context root = "/converter", path = "/converter-app-client'
Java Web Start services started for application com.sun.enterprise.appclient.jws.ApplicationContentOrigin@c91c07

registration name=converter
com.sun.enterprise.appclient.jws.NestedAppclientContentOrigin@14f3900 registration name=converter, context

root=/converter/converter-app-client, module name=
, parent=converter
WEB0100: Loading web module [converter:converter-war.war] in virtual server [server] at [/converter]Class [ Lconverter/ejb/Converter; ] not found. Error while loading [ class converter.client.ConverterClient ]
Error in annotation processing: java.lang.NoClassDefFoundError: Lconverter/ejb/Converter;
deployed with moduleid = converter-app-client

Converter-app-client side

Caught an unexpected exception! java.lang.NullPointerException
at converter.client.ConverterClient.doConversion(ConverterClient.java:59)
at converter.client.ConverterClient.main(ConverterClient.java:53)
Here is the JNDI listing in ASADMIN:

C:\>asadmin
Use "exit" to exit and "help" for online help.
asadmin> list-jndi-entries
Jndi Entries for server within root context:
converter.ejb.Converter: javax.naming.Reference
converter.ejb.Converter#converter.ejb.Converter: javax.naming.Reference
jbi: com.sun.enterprise.naming.TransientContext
jdbc: com.sun.enterprise.naming.TransientContext
UserTransaction: com.sun.enterprise.distributedtx.UserTransactionImpl
ejb: com.sun.enterprise.naming.TransientContext
converter.ejb.Converter__3_x_Internal_RemoteBusinessHome__: javax.naming.Reference
Command list-jndi-entries executed successfully.
asadmin>

My questions are:

( a ) Why does the error occur?
( b ) what is the architecture difference in accessing the same bean? Does JNDI lookup allows one to access EJB from remote host as opposed the method ( ii ) which is only restricted to local access on the same JVM/Container?
( c ) What are the pros & cons between the two?

I am using Application Client to lookup these Session Beans on Netbeans 5.5, SJSAS 9.0, SDK 1.5.0_11 on Windows XP platform.

Any guideance/advice would be very much appreciated.

Thanks alot,

Henry

[tsvet gergi]

change bean class declaration to: public class ConverterBean implements Converter
it works like this