Getting a target resource based on the client request!

By RESTful way, we have to deliver correct resources to a client request, cccording to the context. For example, if the request is “/users/{uid}”, we will list information about the user that has ID=uid and if the request = “/users/{uid}/items/”, the list of items bought by the {uid} has to be listed. This tutorial try to make the resource routing clear.

1. Create the “forthREST” package and a class named “RESTDistributor” inside the package.
2. Add the following codes:
   
   

   package forthREST;
    
   import org.restlet.Component;
   import org.restlet.data.Protocol;
    
   public class RESTDistributor {
    
   	/**
   	 * @param args
   	 * @throws Exception 
   	 */
   	public static void main(String[] args) throws Exception {
   		// TODO Auto-generated method stub
   		// Create a new Restlet component and add a HTTP server connector to it  
   		Component component = new Component();  
   		component.getServers().add(Protocol.HTTP, 8182); 
    
   		// Attach the application to the component and start it  
   		component.getDefaultHost().attach(new RouterApplication());  
   		component.start();  
   	}	 
    
   }

3. Next, create the “RouterApplication” class to receive client request and deliver them to correct resources. Then add the following codes:
   
   

   package forthREST;
    
   import org.restlet.Application;
   import org.restlet.Restlet;
   import org.restlet.routing.Router;
    
   public class RouterApplication extends Application{
   	/**
   	 * Creates a root Restlet that will receive all incoming calls.
   	 */
   	@Override
   	public synchronized Restlet createInboundRoot() {
   		// Create a router Restlet that routes each call to a new respective instance of resource.
   		Router router = new Router(getContext());
   		// Defines only two routes
   		router.attach("/users/{uid}", UserResource.class);
   		router.attach("/users/{uid}/items", UserItemResource.class);
   		return router;
   	}
   }

4. Create two Java classes named “UserResource” and “UserItemResource” for the respective client request executions.
5. Add the following codes into the “UserResource” class:
   
   

   package forthREST;
    
   import org.restlet.resource.Get;
   import org.restlet.resource.ServerResource;
    
   public class UserResource extends ServerResource {  	
   	@Get  
   	public String toString() {
   		String uid = (String) getRequestAttributes().get("uid");
   		return "Information about user \"" + uid + "\" is: <nothing>";  
   	}  
   }  

6. And the following for the “UserItemResource”:
   
   

   package forthREST;
    
   import org.restlet.resource.Get;
   import org.restlet.resource.ServerResource;
    
   public class UserItemResource extends ServerResource {  
   	@Get  
   	public String toString() {  
   		String uid = (String) getRequestAttributes().get("uid");
   		return "The items that user \"" + uid + "\" bought are: <nothing>";  
   	}  
   }  

7. Finish coding. Now, run the server (RESTDistributor class) for listening request.
8. Navigate http://localhost:8182/users/123, then http://localhost:8182/users/123/items, then others to see the results.
9. Done.