Explained: How to Integrate GWT with Spring 2.0

Sounds good, except for the part where I should edit the web.xml. It is generated, and thus not editable. What is best setup here?

The simplest way =)

import javax.servlet.ServletContext;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;



import org.springframework.web.context.ServletContextAware;

import org.springframework.web.servlet.ModelAndView;

import org.springframework.web.servlet.mvc.Controller;



import com.google.gwt.user.server.rpc.RemoteServiceServlet;



public class GWTController extends RemoteServiceServlet implements Controller,

		ServletContextAware {

	private ServletContext servletContext;



	public ModelAndView handleRequest(HttpServletRequest request,

			HttpServletResponse response) throws Exception {

		super.doPost(request, response);

		return null;



	}



	public ServletContext getServletContext() {

		return servletContext;

	}



	public void setServletContext(ServletContext servletContext) {

		this.servletContext = servletContext;

	}



}

I have described how I integrated Spring without loosing "out of the box GWT works in the IDE with the Shell" in my blog.

Could be a good start for beginners...

http://adminsight.de/2008/02/14/non-invasive-gwt-and-spring-integration/

The link to the author is wrong, it should be gwttips.blogspot.com (not gwttips.blogpspot.com).

Dear all how can i configure the web.xml to load the spring context (DispatcherServlet?) in the host mode note that every time the GWT Shell create a new web.xml file without taking in consideration my xml, i need to use the host mode .. please help..

IMHO a more cleaner way: http://blog.digitalascent.com/2007/11/gwt-rpc-with-spring-2x_12.html

I found no way to edit my previous content. The link to my blog posting is:

http://pgt.de/2008/02/14/non-invasive-gwt-and-spring-integration/

to send objects over rpc which implement java.io.Serializable instead of IsSerializable? replace the return statement with the code below:

return RPC.invokeAndEncodeResponse(this.remoteService, rpcRequest.getMethod(), rpcRequest.getParameters(), rpcRequest.getSerializationPolicy());

hope this helped before you started hitting your head to walls ;) r a f t

Before you start wiring up beans as Gwt-RPC endpoints or start creating lots of RPC services, have a look at the command pattern approach described Ray Ryan at his talk. At the end, all you need is one single service, without loosing type safety.

A wrap up with link to the talk (video) and to the projects that either already where there b4 Ryans talk or were created upon the talk can be found here:

http://pgt.de/2009/09/18/best-practices-for-architecting-your-gwt-app/

There you will find a very simple and concise way to use Spring in the backend with gwt-dispatch.

Have fun!

I'm getting a NullPointerException? when calling the getServletContext(). Anyone has a clue why this happens??

Fixed my NullPointerException??. The above GWTController code should maybe be changed like I described in this post

http://blog.js-development.com/2009/09/gwt-meets-spring.html

I guess more people are having this issue.

Juri

Hi!

Great fix! I was happily using it until I tried to send objects of my own type from client to server when it broke with SerializationException?.

I've got an addition to your fix at:

http://javaagile.blogspot.com/2010/02/ive-just-started-playing-with-googles.html

Thanks once again!

Phill

Why is the fanciness needed? I got it working using Spring MVC annotations and a basic base class for the GWT services. Maybe it's "tied into" Spring MVC too much for your liking?

The base class for GWT services:

public abstract class BaseRemoteService extends RemoteServiceServlet implements ServletContextAware {
	
	private ServletContext servletContext;
	
	@RequestMapping(method = { RequestMethod.GET, RequestMethod.POST })
	public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
		doPost(request, response);
		return null; // response handled by GWT RPC over XmlHttpRequest
	}

	@Override
	public void setServletContext(ServletContext servletContext) {
		this.servletContext = servletContext;
	}
	
	@Override
	public ServletContext getServletContext() {
		return this.servletContext;
	}
}

An example class autowired and mapped using annotations:

@Controller
@RequestMapping("/**/thing.service")
public class ThingService extends BaseRemoteService implements IThingService {
	@Autowired
	private ISystemService systemService;
	
	@Override
	public String getVersion() {
		return systemService.getVersion();
	}
}

And the dispatcher XML contains only the lines:

	<context:component-scan base-package="au.gov.vic.dpi.contactmanager.gwt.server">
        <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    </context:component-scan>

The ISystemService is defined in another XML autowiring by name (it's a remote service) that the ContextLoaderListener? is initialising.

The above is pretty much what dgreen.ru said, but using annotations instead of the Controller interface.

Hi,

Can any one tell me, how do I get the http session in the implementation class as we are not directly implementing RemoteServiceServlet?.

Sree-

The HttpServletRequest? object in the remote service seems to be null. Any one has clue?

Did any one get this exception ???

SEVERE: Exception while dispatching incoming RPC call java.lang.NullPointerException?

at javax.servlet.GenericServlet?.getServletName(GenericServlet?.java:322) at javax.servlet.GenericServlet?.log(GenericServlet?.java:277) at com.google.gwt.user.server.rpc.RemoteServiceServlet?.doGetSerializationPolicy(RemoteServiceServlet?.java:219) at com.google.gwt.user.server.rpc.RemoteServiceServlet?.getSerializationPolicy(RemoteServiceServlet?.java:117) at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader?.prepareToRead(ServerSerializationStreamReader?.java:429) at com.google.gwt.user.server.rpc.RPC.decodeRequest(RPC.java:234) at com.test.server.generic.controller.GWTRPCController.processCall(GWTRPCController.java:94)

Hi ! A piece of code in my server side impl class invokes getThreadLocalRequest() method, which works fine when GWTServletImpl is directly used as a servlet in web.xml.

But when I used GWTController for spring integration, work is delegated to server side impl class using statement:

RPC.invokeAndEncodeResponse(this.remoteService, rpcRequest.getMethod(), rpcRequest.getParameters(), rpcRequest.getSerializationPolicy());

And this.getThreadLocalRequest() invocation in my actual impl class returns null.

How to handle this ? Help !!

kirtigupta06 did you find any solution for the null point on this.getThreadLocalRequest() ??

Any help please????

Hi yogu13, I don't know if can be useful for you now, but I have the same problem. Is because the config object is null inside GenericServlet?. My solution is to implement the interface ServletConfigAware? in GWTController. then put this method

@Override

public void setServletConfig(ServletConfig? servletConfig) {

try {

super.init(servletConfig);

} catch (ServletException? e) {

e.printStackTrace();

}

}

I hope somebody can find this useful

@kirtigupta06, @makhloufelyes

did you find any solution for the null point on this.getThreadLocalRequest() ??

Any help please????

Hi, my GWTController invokes my RemoteService? which has been injected by Spring, But finally it throws following error..

java.lang.NullPointerException?

at javax.servlet.GenericServlet?.getServletContext(GenericServlet?.java:160) at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet?.doUnexpectedFailure(AbstractRemoteServiceServlet?.java:109) at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet?.doPost(AbstractRemoteServiceServlet?.java:67) at com.mycompany.server.GWTController.handleRequest(GWTController.java:43)

Can anyone found any solution for this............

Thanks for posting this code. I'm using GWT RequestFactory? instead of RPC. I have not yet found any good resource on integration of RF + Spring 3.0 or even 2.5+. I have tried myself but unsuccessful. Do you guys know of a resource that talks about this? Any help is much appreciated.

Cheers :)

@EasierWay if you use the code above with GWT2 you might have some issues with serialization because the RemoteServiceServlet changed. Easier way is to check if the member is not null and invoke it, otherwise delegate the call to the superclass. When I attempted using the code "as-is" from the article I was getting various issues because the signatures and method body changed in GWT2.

@SuppressWarnings("serial")
public class SpringControllerGWT extends RemoteServiceServlet
		implements Controller{
	protected RemoteService remoteService;
	protected ServletContext servletContext;


	/**
	 * Implements Spring Controller interface method.
	 * 
	 * Call GWT's RemoteService doPost() method and return null.
	 * 
	 * @param request
	 *            current HTTP request
	 * @param response
	 *            current HTTP response
	 * @return a ModelAndView to render, or null if handled directly
	 * @throws Exception
	 *             in case of errors
	 */
	public ModelAndView handleRequest(HttpServletRequest request,
			HttpServletResponse response) throws Exception {
		if(getRemoteService()!=null){
			Controller controller = (Controller)getRemoteService();
			return controller.handleRequest(request, response);
		}
		doPost(request, response);
		return null; // response handled by GWT RPC over XmlHttpRequest
	}

	/**
	 * Process the RPC request encoded into the payload string and return a
	 * string that encodes either the method return or an exception thrown by
	 * it.
	 */
	@Override
	public String processCall(String payload) throws SerializationException {
		if(getRemoteService()!=null){
			RemoteServiceServlet remoteServlet = (RemoteServiceServlet)getRemoteService();
			return remoteServlet.processCall(payload);
		}
		return super.processCall(payload);
	}

	public Class<?> getRemoteServiceClass() {
		Class<?> retval = null;
		if (getRemoteService() == null) {
			return retval;
		}
		retval = getRemoteService().getClass();
		return retval;
	}

	/**
	 * @return the remoteService
	 */
	public RemoteService getRemoteService() {
		return remoteService;
	}

	/**
	 * @param remoteService
	 *            the remoteService to set
	 */
	public void setRemoteService(RemoteService remoteService) {
		this.remoteService = remoteService;
	}
}

Hi. I'm trying to make a flexible solution to this problem. - resolve service by URL; - resolve service by Annotation;

http://code.google.com/p/gwt-delegate/

http://code.google.com/p/gwt-delegate/source/browse/gwt-delegate-parent/gwt-delegate/src/main/java/org/sgtools/gwt/delegate