Introduction

GWT uses asynchronous RPC between client (e.g Browser) and RemoteService servlet.

GWT SyncProxy provides synchronous RPC between Java client and RemoteService servlet. By using SyncProxy, we can invoke the GWT RemoteService methods from pure Java (no JSNI) code.

Usage

The service interface

For example, we have an helloApp application and our GreetingService:

@RemoteServiceRelativePath("greet")
public interface GreetingService extends RemoteService {
  String greetServer(String name);
}

And the service implementation:

public class GreetingServiceImpl extends RemoteServiceServlet
      implements GreetingService {
  public String greetServer(String name) {
    return "Hello, " + name;
  }
}

Compile the helloApp and deploy it to a web server. For example, the application is deployed and servlet URL is configured at http://example.com/helloApp/greet

Java client code

Create new proxy instance for the service interface:

private static GreetingService rpcService =
  SyncProxy.newProxyInstance(GreetingService.class,
        "http://example.com/helloApp", "greet");

SyncProxy.newProxyInstance() method requires a service interface class, a base URL and a relative servlet path.

Then invoke the RPC method:

String result = rpcService.greetServer("SyncProxy");

Simulating Async

Create new proxy instance for the Async service interface:

private static GreetingServiceAsync rpcServiceAsync =
  SyncProxy.newProxyInstance(GreetingServiceAsync.class,
        "http://example.com/helloApp", "greet");

Then invoke the RPC method asynchronously:

rpcServiceAsync.greetServer("SyncProxy", new AsyncCallback(){
  public void onFailure(Throwable caught) {
    ...
  }
  public void onSuccess(String result) {
    ...
  }
});

Multiple sessions

Form version 0.3, SyncPoryy use standard Java java.net.CookieManager to manage client session.

CookieManager empSession = new CookieManager(null, CookiePolicy.ACCEPT_ALL);
CookieManager mgrSession = new CookieManager(null, CookiePolicy.ACCEPT_ALL);
GreetingService empRpcService =
  SyncProxy.newProxyInstance(GreetingService.class,
        "http://example.com/helloApp", "greet", empSession);
GreetingService mgrRpcService =
  SyncProxy.newProxyInstance(GreetingService.class,
        "http://example.com/helloApp", "greet", mgrSession);

Invoke GWT RPC services deployed on AppEngine

For security-enabled RPC services deployed on AppEngine, we have to login before calling RPC methods.

CookieManager userSession = LoginUtils.loginAppEngine("https://example.appspot.com",
    "http://example.appspot.com/helloApp/greet",
    "emailaddress@gmail.com", "password");

Then invoke the RPC method:

private static GreetingService rpcService =
  SyncProxy.newProxyInstance(GreetingService.class,
        "http://example.appspot.com/helloApp", "greet", userSession);

String result = rpcService.greetServer("SyncProxy");

Release notes

• 20/08/2011 - Version 0.3:
• Use standard Java CookieManager
• Fixed  issue 17 
• Auto fetch Serialization Policy Files from server base on the patch described in  issue 13 .

• 13/11/2010 - Version 0.2:
• Fixed  issue 2 ,  issue 4  and  issue 9 
• Multiple sessions as described in  issue 6 .