With this example we are going to show you how to perform basic operations over a binding in a Naming service, that is locating adding replacing removing and renaming a binding in the Naming service.
In order to run this example you should first follow the one describing how to implement a simple “calculator” service capable of RMI invocations here.
You must implement, compile, create the CalculatorServiceImpl “stub” class and launch the rmiregistry to use its Naming service.
Let’s see the code:
package com.javacodegeeks.snippets.enterprise;
import java.rmi.RemoteException;
import java.util.Hashtable;
import javax.naming.Binding;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
public class AddLookupReplaceRemoveRenameBindings {
public static void main(String[] args) {
try {
/*
* This example uses the RMI Registry naming service provider running on
* local host and on the default port (1099)
*
* For connecting to alternate naming service providers you should construct
* a Hashtable containing appropriate environment directives and initialize the
* InitialContext Object using the InitialContext(Hashtable env) constructor
* injecting the environment table.
*
* For example; connecting to JBoss naming service running on local host the
* environment that should be created is like the one shown below :
*
* Hashtable env = new Hashtable();
* env.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory");
* env.put(Context.PROVIDER_URL, "jnp://localhost:1099");
* env.put(Context.URL_PKG_PREFIXES, "org.jboss.naming:org.jnp.interfaces");
*
*/
Hashtable env = new Hashtable();
env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.rmi.registry.RegistryContextFactory");
env.put(Context.PROVIDER_URL, "rmi://localhost:1099");
Context ctx = new InitialContext(env);
System.out.println("Initial Context created successfully");
// Add a binding. Object to bind must be Remote, Reference, or Referenceable
ctx.bind("Calculator_Service", new CalculatorServiceImpl());
// Display all bindings of the context
NamingEnumeration bindings = ctx.listBindings(ctx.getNameInNamespace());
System.out.println("After adding 'Calculator_Service' binding, Naming Context contains :");
while(bindings.hasMore()) {
Binding binding = (Binding)bindings.next();
System.out.println("Binding name : " + binding.getName() + ", Binding Object hashCode : " + binding.getObject().hashCode());
}
// Replace a binding. Object to bind must be Remote, Reference, or Referenceable
ctx.rebind("Calculator_Service", new CalculatorServiceImpl());
// Display all bindings of the context
bindings = ctx.listBindings(ctx.getNameInNamespace());
System.out.println("After rebinding 'Calculator_Service', Naming Context contains :");
while(bindings.hasMore()) {
Binding binding = (Binding)bindings.next();
System.out.println("Binding name : " + binding.getName() + ", Binding Object hashCode : " + binding.getObject().hashCode());
}
// Looking up an object by its binding name
CalculatorService calculator = (CalculatorService)ctx.lookup("Calculator_Service");
System.out.println("Calculating 2 + 2 = " + calculator.add(2, 2));
// Rename a binding
ctx.rename("Calculator_Service", "New_Calculator_Service");
// Display all bindings of the context
bindings = ctx.listBindings(ctx.getNameInNamespace());
System.out.println("After replacing 'Calculator_Service' with 'New_Calculator_Service' binding, Naming Context contains :");
while(bindings.hasMore()) {
Binding binding = (Binding)bindings.next();
System.out.println("Binding name : " + binding.getName() + ", Binding Object hashCode : " + binding.getObject().hashCode());
}
// Looking up an object by its binding name
calculator = (CalculatorService)ctx.lookup("New_Calculator_Service");
System.out.println("Calculating 10 / 2 = " + calculator.div(10, 2));
// Remove a binding
ctx.unbind("New_Calculator_Service");
// Display all bindings of the context
bindings = ctx.listBindings(ctx.getNameInNamespace());
System.out.println("After removing 'New_Calculator_Service' binding, Naming Context contains :");
while(bindings.hasMore()) {
Binding binding = (Binding)bindings.next();
System.out.println("Binding name : " + binding.getName() + ", Binding Object hashCode : " + binding.getObject().hashCode());
}
} catch (NamingException e) {
System.out.println("Exception occurred while utilizing bindings : " + e.getMessage());
} catch (RemoteException e) {
System.out.println("Could not create calculator service : " + e.getMessage());
}
}
}
Example Output:
Initial Context created successfully
After adding 'Calculator_Service' binding, Naming Context contains :
Binding name : Calculator_Service, Binding Object hashCode : 853137463
After rebinding 'Calculator_Service', Naming Context contains :
Binding name : Calculator_Service, Binding Object hashCode : 394882503
Calculating 2 + 2 = 4
After replacing 'Calculator_Service' with 'New_Calculator_Service' binding, Naming Context contains :
Binding name : New_Calculator_Service, Binding Object hashCode : 394882503
Calculating 10 / 2 = 5.0
After removing 'New_Calculator_Service' binding, Naming Context contains :
This is an example on locating, adding, replacing, removing and renaming a binding in the Naming service.
