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**marbot** · 29 Jun 2010, 00:58

Hi db75

I'm not sure it's what you're looking for, but consider this previous post from madamovic:

http://forums.smartclient.com/showth...3616#post43616

Besides, you do not need to change the fetch()-method signatur if you throw (unchecked) runtime-exceptions. The SmartGWT-Framework will propagate the exception to the client, and you should be able to get the exceptions in the onFailure()-method.

marbot

**db75** · 29 Jun 2010, 02:13

I agree however this kind of code generate a NPE sometimes :

Code:

public List<YourDataObject> fetch() {
		System.out.println("fetch inside YourServiceImpl");
		
		items.clear();
		
		ViewDTO vd = new ViewDTO();

		SAXReader reader = new SAXReader();
		try{
				Document document = WorkeyAPIUtils.getXMLInput(new APIClient("http://localhost:6060/api/View/1", user, "test").get(""));
				Node fromNode = document.selectSingleNode("/w:view/@xlink:href");			
				vd.setDesignerName(fromNode.getText());
				
				YourDataObject item4 = new YourDataObject();
				item4.setId(5);
				item4.setName(vd.getDesignerName());
				item4.setFuck(vd.getWkyId());
				items.add(item4);
		}
		catch (Exception e) {
			throw new RuntimeException(e);
		}
		return items;
	}

The fact is I've got the following error which should'nt be in the log as a SEVERE error as it is intended and should be catch inside the async call in the datasource

Code:

29 juin 2010 12:06:27 com.google.appengine.tools.development.ApiProxyLocalImpl log
SEVERE: [1277805987684000] javax.servlet.ServletContext log: Exception while dispatching incoming RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract java.util.List com.clog.gwt.client.GenericGwtRpcDataSourceService.fetch()' threw an unexpected exception: java.lang.RuntimeException: java.lang.NullPointerException
	at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:378)
	at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:581)
	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:188)
	at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:224)
	at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:713)

**db75** · 29 Jun 2010, 04:26

And in developpement view (eclipse) I've got :

Code:

14:16:24.366 [ERROR] [helloworld] 14:16:24.347:WARN:RPCManager:Error performing rpcRequest: error: FAILURE, response: {clientContext: Obj, status: -1, context: undef, startRow: 0, endRow: 0, totalRows: 0}
com.smartgwt.client.core.JsObject$SGWT_WARN: 14:16:24.347:WARN:RPCManager:Error performing rpcRequest: error: FAILURE, response: {clientContext: Obj, status: -1, context: undef, startRow: 0, endRow: 0, totalRows: 0}
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:105)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannel.reactToMessagesWhileWaitingForReturn(BrowserChannel.java:1713)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:165)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:120)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:507)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeVoid(ModuleSpace.java:284)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeVoid(JavaScriptHost.java:107)
    at com.smartgwt.client.data.DataSource.processResponse(DataSource.java)
    at com.clog.gwt.client.GenericGwtRpcDataSource$1.onFailure(GenericGwtRpcDataSource.java:134)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:218)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:393)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannel.reactToMessagesWhileWaitingForReturn(BrowserChannel.java:1713)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:165)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:120)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:507)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:264)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:188)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannel.reactToMessages(BrowserChannel.java:1668)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:401)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:222)
    at java.lang.Thread.run(Unknown Source)

The fact is that the datasource which make the call to async service does'nt display any alert

Code:

@Override
	public YourServiceAsync getServiceAsync() {
		System.out.println("creation of YourService.class");
		Window.alert("test");
		//return new YourService();
		
		YourServiceAsync ysa = (YourServiceAsync)GWT.create(YourService.class);	
		 AsyncCallback<String> callback = new AsyncCallback<String>() {
		      public void onFailure(Throwable caught) {
		    	  
		        Window.alert(caught.toString());
		      }

		      public void onSuccess(String result) {
		    	  
		      }
		 };
		
		ysa.setUserName("test", callback);
		//ysa.password="test";		
		return ysa;
	}

**Principal Skiner** · 29 Jun 2010, 12:53

Hi guys.
I ran into a problem with this implementation of data source when using GWT with Seam on the server side.
The problem manifests itself on the server side when RPC is made. The logic on the server side tries to find Seam component using the name of the service interface. It tries to find "GenericGwtRpcDataSource" Seam component which does not exist. And it should not.
I found a place where this can be solved but there is a problem.
In GenericGwtRpcDataSource.executeFetch, the serviceAsync could be cast to its real type and therefore avoid the problem.
I tried using Class.cast method but GWT 2.0.2 compiler cannot find it.
Any suggestions?

**marbot** · 29 Jun 2010, 13:34

Originally posted by Principal Skiner

Hi guys.
I ran into a problem with this implementation of data source when using GWT with Seam on the server side.
The problem manifests itself on the server side when RPC is made. The logic on the server side tries to find Seam component using the name of the service interface. It tries to find "GenericGwtRpcDataSource" Seam component which does not exist. And it should not.
I found a place where this can be solved but there is a problem.
In GenericGwtRpcDataSource.executeFetch, the serviceAsync could be cast to its real type and therefore avoid the problem.
I tried using Class.cast method but GWT 2.0.2 compiler cannot find it.
Any suggestions?

Hi Seymour

I suppose GWT can't translate Class.cast to Javascript... I came across com.google.gwt.lang.Cast, maybe you could use it?

see http://code.google.com/p/google-web-...c=svn7855&r=92

cheers

**marbot** · 29 Jun 2010, 13:40

Hi Denis

Madamovic mentioned the following in his post:

1. On the server, handle all exceptions and wrap them into Exception (java.lang.Exception), because only Exception can propagate properly to the client.

...so maybe you could try a "try / catch" block? ...I suppose I was wrong with the Runtime-Exceptions (it's GWT after all, not plain Java), so maybe you need to alter the method signatur to throw a (plain old) java.lang.Exception?

...sorry, I can't help you on that one at the moment, I've got too much to do and too little time lately... :-)

please post any result you might get

thanks
marbot

**Principal Skiner** · 29 Jun 2010, 13:44

Thanks for the quick reply Marbot.
Unfortunately the casting won't solve the problem. I have heartlessly removed all your generics thus made the GenericGwtRpcDataSource quite non-generic and the problem still persists. I'm 99% certain it is because of my service interface extends GenericGwtRpcService. I'll keep digging...

**marbot** · 29 Jun 2010, 14:07

Originally posted by Principal Skiner

Thanks for the quick reply Marbot.
Unfortunately the casting won't solve the problem. I have heartlessly removed all your generics thus made the GenericGwtRpcDataSource quite non-generic and the problem still persists. I'm 99% certain it is because of my service interface extends GenericGwtRpcService. I'll keep digging...

...Maybe it's too simple to work, but why don't we avoid the cast by making serviceAsync generic as well? (What I should have done from the beginning, when I think about it :-)) ...Does the following simple change work?

Code:

public abstract class GenericGwtRpcDataSource<D, R extends Record, SA extends GenericGwtRpcServiceAsync<D>>
		extends GwtRpcDataSource {
	
	//private GenericGwtRpcServiceAsync<D> serviceAsync;
	private SA serviceAsync;

Note that I do not know Seam very well, just guessing... Avoiding using GenericGwtRpcServiceAsync in the first place might solve the casting problem...

**db75** · 30 Jun 2010, 01:00

Originally posted by marbot

Hi Denis

Madamovic mentioned the following in his post:

...so maybe you could try a "try / catch" block? ...I suppose I was wrong with the Runtime-Exceptions (it's GWT after all, not plain Java), so maybe you need to alter the method signatur to throw a (plain old) java.lang.Exception?

The fact of launching a Plain old java Exception make mandatory to add throws Exception on the signature of fetch method. So it is what I have done. Then when I execute this coding I've got the following error :

Code:

10:57:06.291 [ERROR] [helloworld] 10:57:06.309:WARN:RPCManager:Error performing rpcRequest: error: FAILURE, response: {clientContext: Obj, status: -1, context: undef, startRow: 0, endRow: 0, totalRows: 0}
com.smartgwt.client.core.JsObject$SGWT_WARN: 10:57:06.309:WARN:RPCManager:Error performing rpcRequest: error: FAILURE, response: {clientContext: Obj, status: -1, context: undef, startRow: 0, endRow: 0, totalRows: 0}
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:105)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannel.reactToMessagesWhileWaitingForReturn(BrowserChannel.java:1713)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:165)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:120)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:507)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeVoid(ModuleSpace.java:284)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeVoid(JavaScriptHost.java:107)
    at com.smartgwt.client.data.DataSource.processResponse(DataSource.java)
    at com.clog.gwt.client.GenericGwtRpcDataSource$1.onFailure(GenericGwtRpcDataSource.java:134)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:218)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:393)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannel.reactToMessagesWhileWaitingForReturn(BrowserChannel.java:1713)
    at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:165)
    at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:120)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:507)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:264)
    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
    at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
    at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:188)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
    at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:157)
    at com.google.gwt.dev.shell.BrowserChannel.reactToMessages(BrowserChannel.java:1668)
    at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:401)
    at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:222)
    at java.lang.Thread.run(Unknown Source)

**Principal Skiner** · 30 Jun 2010, 08:45

Problem with Seam solved.
So I had a service interface like this :

Code:

public interface AlertWebService extends GenericGwtRpcService<AlertReport> {

  public AlertReport[] findAlerts(...)
}

Calling the findAlert() via RPC worked fine as before even after extending the GenericGwtRpcService interface. But calling the executeFetch caused problem on the server side. Seam was trying to find a component by the name "GenericGwtRpcService" but it should have been "AlertWebService".
Reason :
fetch method is located in GenericGwtRpcService interface so the name of the interface gets resolved to a Seam component's name.
Solution (not the prettiest I admit) :
copy the executeFetch method to AlertWebService. The method is duplicated in both interfaces but that's the best I could think of right now.
After the workaround :

Code:

public interface AlertWebService extends GenericGwtRpcService<AlertReport> {
  public AlertReport[] findAlerts(...)
  List<AlertReport> fetch (...)
}

P.S.
Seam users are probably familiar with the patch found here: http://virgo47.wordpress.com/2010/02...gwt-2-support/
That is where component is sought after the name of service interface

**Principal Skiner** · 30 Jun 2010, 08:54

This brings me to another problem.
I am using custom criteria on my ListGrid.
When I call :

Code:

grid.fetchData(customCriteria)

criteria contains no keys or values that I defined. There is only "__gwt_ObjectId" as key mapped to some numeric value.
Calling :

Code:

grid.getDataSource().fetchData(customCriteria)

sends the custom criteria to the server side almost properly. I say almost because that "__gwt_ObjectId" is still present in criteria map together with my mappings.
Any thoughts on this? Should that "__gwt_ObjectId" key be always present?

Edit :
Problem with fetch is solved. __gwt_ObjectId is still present in the map but causes no real problems. So I'll just leave it there :)

**aznan** · 3 Aug 2010, 15:44

Hi!
I'm a total n00b in this area. I really like how easy it is to build advanced user interfaces using SmartGWT, but getting the data up has been a real hassle. Thanks to the ListGridTest I've finally gotten single class loading to work, but I have since spent an entire day trying to get a one-to-many relationship to work with no luck.

Can anyone give me any pointers on how to accomplish this?
Thanks!

**marbot** · 11 Aug 2010, 07:44

Originally posted by aznan

Hi!
I'm a total n00b in this area. I really like how easy it is to build advanced user interfaces using SmartGWT, but getting the data up has been a real hassle. Thanks to the ListGridTest I've finally gotten single class loading to work, but I have since spent an entire day trying to get a one-to-many relationship to work with no luck.

Can anyone give me any pointers on how to accomplish this?
Thanks!

Hi aznan

Well, this is where the actual GenericGwtRpcDataSource is limited. The SmartGWT EE Package offers ways to deal with one-to-many relationships without having to write code, but the GenericGwtRpcDataSource requests you to write your own code to deal with the Database. I cannot help you here. Have a look at the SmartGwt EE Package, maybe it fits your needs.

marbot

**aznan** · 11 Aug 2010, 22:08

Too bad. And since I'm just a hobbyist, $700 is a little steep for something to put on my home server :P
Thanks for the reply, though!
/aznan

**jrich** · 15 Aug 2010, 01:13

Hi Marbot,

I have been using your code perfectly for a while now, thank you.
I was just wondering if you had ever looked at file uploads form a form using it and if so, if you had any pointers?

Kind Regards
Jen

Not to worry, I have used a servlet!

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