Getting "StatusCodeException" when trying to execute action - gwt-rpc

Question

i am using GWT/GWTP (2.6.0/1.2.1). I am trying to execute an Action. The action itself is just a signal (no logic or data elements). The result is supposed to carry an ArrayList of DTOs.
When i use the exact same setup with another action (containing a string) it works fine.
I get this error:
[ERROR] com.google.gwt.user.client.rpc.StatusCodeException: 500 Server
Error The call failed on the server; see server log for details
[ERROR] at
com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:209)
[ERROR] at
com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:259)
[ERROR] at
com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:412)
[ERROR] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native
Method) [ERROR] at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
[ERROR] at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[ERROR] at java.lang.reflect.Method.invoke(Method.java:606) [ERROR]
at
com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
[ERROR] at
com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
[ERROR] at
com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
[ERROR] at
com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:338)
[ERROR] at
com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
[ERROR] at
com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
[ERROR] at
com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:576)
[ERROR] at
com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:284)
[ERROR] at
com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
[ERROR] at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
[ERROR] at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:347)
[ERROR] at sun.reflect.GeneratedMethodAccessor51.invoke(Unknown
Source) [ERROR] at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[ERROR] at java.lang.reflect.Method.invoke(Method.java:606) [ERROR]
at
com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
[ERROR] at
com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
[ERROR] at
com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
[ERROR] at
com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:293)
[ERROR] at
com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
[ERROR] at
com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
[ERROR] at java.lang.Thread.run(Thread.java:744)
What do i miss?
My Action looks like this:
package testproject.shared.dispatch;
import com.gwtplatform.dispatch.rpc.shared.UnsecuredActionImpl;
public class FetchDevicesAction extends UnsecuredActionImpl<FetchDevicesResult> {
public FetchDevicesAction() {
}
}
My Result like this (is this where the problem lies?):
package testproject.shared.dispatch;
import java.util.List;
//import org.apache.log4j.xml.DOMConfigurator;
import testproject.shared.dto.DeviceDto;
import com.allen_sauer.gwt.log.client.Log;
import com.gwtplatform.dispatch.rpc.shared.Result;
public class FetchDevicesResult implements Result {
/**
*
*/
private static final long serialVersionUID = -6478205044537244983L;
private List<DeviceDto> deviceDtos;
public FetchDevicesResult(List<DeviceDto> deviceDtos) {
this.deviceDtos = deviceDtos;
}
public List<DeviceDto> getDeviceDtos() {
return deviceDtos;
}
}
Here is part of my presenter:
public class DevicesPresenter extends
Presenter<DevicesPresenter.MyView, DevicesPresenter.MyProxy> implements
DevicesUiHandlers {
Logger logger = Logger.getLogger("RootLogger");
List<Device> devices = null;
List<DeviceDto> deviceDtos = null;
/**
* {#link DevicesPresenter}'s proxy.
*/
#ProxyCodeSplit
#NameToken(NameTokens.devicesPage)
#TabInfo(container = ApplicationPresenter.class, label = "Devices", priority = 1)
// The third tab in the main page
public interface MyProxy extends TabContentProxyPlace<DevicesPresenter> {
}
/**
* {#link DevicesPresenter}'s view.
*/
public interface MyView extends View, HasUiHandlers<DevicesUiHandlers> {
CellTable<Device> getCellTable();
}
private DispatchAsync dispatcher;
#Inject
DevicesPresenter(EventBus eventBus, MyView view, MyProxy proxy,
final DispatchAsync dispatcher) {
super(eventBus, view, proxy, ApplicationPresenter.SLOT_SetTabContent);
this.dispatcher = dispatcher;
view.setUiHandlers(this);
}
public void fetchDevicesTask() {
FetchDevicesAction action = new FetchDevicesAction();
Log.debug("Executing FetchDevices");
dispatcher.execute(action, new AsyncCallbackImpl<FetchDevicesResult>() {
#Override
public void onSuccess(FetchDevicesResult result) {
Log.debug("onSuccess");
deviceDtos = result.getDeviceDtos();
}
});
}
The shared libraries are part of my gwt.xml.
My DeviceDto:
package testproject.shared.dto;
import java.io.Serializable;
public class DeviceDto implements Serializable {
private static final long serialVersionUID = 3434148714982575460L;
protected Long DeviceId;
protected String Image;
protected String FirmwareVersion;
public DeviceDto() {
this.DeviceId = -1L;
}
public DeviceDto(Long DeviceId) {
this.DeviceId = DeviceId;
}
public DeviceDto(Long DeviceId, String Image, String FirmwareVersion) {
this.DeviceId = DeviceId;
this.Image = Image;
this.FirmwareVersion = FirmwareVersion;
}
public Long getDeviceId() {
return DeviceId;
}
public void setDeviceId(Long DeviceId) {
this.DeviceId = DeviceId;
}
public String getImage() {
return Image;
}
public void setImage(String Image) {
this.Image = Image;
}
public String getFirmwareVersion() {
return FirmwareVersion;
}
public void setFirmwareVersion(String FirmwareVersion) {
this.FirmwareVersion = FirmwareVersion;
}
My Handler (even though i think it does not get this far):
package testproject.server.dispatch;
import java.util.ArrayList;
import java.util.List;
import org.apache.log4j.xml.DOMConfigurator;
import testproject.server.dao.DeviceDao;
import testproject.shared.dispatch.FetchDevicesAction;
import testproject.shared.dispatch.FetchDevicesResult;
import testproject.shared.domain.Device;
import testproject.shared.dto.DeviceDto;
import com.allen_sauer.gwt.log.client.Log;
import com.google.inject.Inject;
import com.gwtplatform.dispatch.rpc.server.ExecutionContext;
import com.gwtplatform.dispatch.shared.ActionException;
public class FetchDevicesHandler extends AbstractAction<FetchDevicesAction, FetchDevicesResult> {
#Inject
FetchDevicesHandler() {
super(FetchDevicesAction.class);
DOMConfigurator.configure("log4j.xml");
}
#Override
public FetchDevicesResult execute(FetchDevicesAction action, ExecutionContext context) throws ActionException {
FetchDevicesResult result = null;
DeviceDao deviceDao = new DeviceDao();
Log.debug("Retrieve Devices");
try {
List<Device> devices = deviceDao.retrieveDevices();
if (devices != null) {
List<DeviceDto> deviceDtos = new ArrayList<DeviceDto>(devices.size());
for (Device device : devices) {
Log.debug("Adding Device to dto list: " + device.getDeviceId().toString());
deviceDtos.add(createDeviceDto(device));
}
result = new FetchDevicesResult(deviceDtos);
}
}
catch (Exception e) {
Log.warn("Unable to retrieve Accounts - ", e);
throw new ActionException(e);
}
return result;
}
private DeviceDto createDeviceDto(Device device) {
return new DeviceDto(device.getDeviceId(), device.getImage(), device.getFirmwareVersion());
}
}
I googled and searched stackoverflow, but this error message seems not to happen anywhere else.
Thank you for your help :)
}