Wednesday, September 15, 2010

Re: Unchecked exceptions from server to client

After closer examination, this solution is not good enough. Examine the stacktrace below;

SEVERE: [1284616090213000] javax.servlet.ServletContext log: Exception while dispatching incoming RPC call

com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract void com.netgazelle.client.service.AccountService.createAccount(java.lang.String,java.lang.String,java.lang.String,java.lang.String,java.util.Date,java.lang.String,java.lang.String,java.lang.String,java.lang.String) throws com.netgazelle.shared.CreateException' threw an unexpected exception: com.netgazelle.shared.DuplicatePhoneCreationException

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)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)

at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)

at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:58)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)

at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)

at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:122)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)

at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)

at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)

at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)

at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)

at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)

at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:70)

at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)

at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:349)

at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)

at org.mortbay.jetty.Server.handle(Server.java:326)

at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)

at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)

at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)

at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)

at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)

at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)

at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

Caused by: com.netgazelle.shared.DuplicatePhoneCreationException

at com.netgazelle.server.manager.AccountManager.createAccount(AccountManager.java:285)

at com.netgazelle.server.service.AccountServiceImpl.createAccount(AccountServiceImpl.java:74)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:100)

at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:562)

... 30 more


My problem lies in RPC.java line 377; !RPCServletUtils.isExpectedException(serviceMethod, cause))

The function RPCServletUtils.isExpectedException does not take this into consideration;

--> if the cause is an unchecked exception
--> if the cuase is an subclass instance of an defined and checked exception

The workaround seems to be to define the explicit exceptions throws in the service interface.

Does anyone have a reason for why I should not report this a bug in the issue tracker ? 

Thanks,

:-) Kasper

On Tue, Sep 14, 2010 at 8:50 AM, San0 <sanopl@gmail.com> wrote:
> Your service probably extends RemoteServiceServlet, which is catching
> all non declared exceptions. Simple solution is to create your own
> RemoteServiceServlet implementation with overridden:
> String processCall(String payload) throws SerializationException
> Something like this:
>
> try {
>      RPCRequest rpcRequest = RPC.decodeRequest(payload,
> delegate.getClass(), this);
>      onAfterRequestDeserialized(rpcRequest);
>      return RPC.invokeAndEncodeResponse(delegate,
> rpcRequest.getMethod(),
>          rpcRequest.getParameters(),
> rpcRequest.getSerializationPolicy(),
>          rpcRequest.getFlags());
>    } catch (IncompatibleRemoteServiceException ex) {
>      log("An IncompatibleRemoteServiceException was thrown while
> processing this call.",ex);
>      return RPC.encodeResponseForFailure(null, ex);
>    } catch (Exception ex) {
>      // RuntimeException
>      return RPC.encodeResponseForFailure(null, new
> GwtClientException(ex.getCause().getMessage()));
>    }
>
> try-catch is from GWT sources, 2nd catch is what u need to re-throw
> exceptions to client.
>
> On Sep 13, 9:24 pm, Kasper Hansen <kbhdk1...@gmail.com> wrote:
>> Hi,
>>
>> I have this;
>>
>> public abstract class CreateException extends RuntimeException implements
>> Serializable {
>>
>> }
>>
>> Notice that I extend from RuntimeException, making it an unchecked
>> exception.
>>
>> Then I have these two;
>>
>> public class DuplicateEmailCreationException extends CreateException {
>>
>> }
>>
>> public class DuplicatePhoneCreationException extends CreateException {
>>
>> }
>>
>> My service is this one;
>>
>> @RemoteServiceRelativePath("AccountService")
>> public interface AccountService extends RemoteService {
>>
>> public void createAccount(String phone, String email);
>>
>> }
>>
>> Notice I don't declare my CreateException using the "throws" keyword.
>>
>> Now I would expect my view to work. It's this one;
>>
>> ...
>> accountServiceAsync.createAccount(tbPhone.getValue(), tbEmail.getValue(),
>> new AsyncCallback<Void>() {
>>
>> public void onSuccess(Void result) {
>>
>> }
>>
>> public void onFailure(Throwable exception) {
>>
>> if ( exception instanceof DuplicatePhoneCreationException) {
>>
>> // handle it
>>
>> }
>>
>> else {
>>
>> if (exception instanceof DuplicateEmailCreationException) {
>>
>> // handle it
>>
>> }
>> }
>> }
>>
>> ...
>>
>> However, it does not work. But if I add the "throws CreateException" in the
>> AccountService's createAccount method, it works fine.
>>
>> The whole point with unchecked exceptions, is that I don't have to define
>> them everywhere. Is this not supported ? Or what am I doing wrong here ?
>>
>> Thanks,
>>
>> :-) Kasper
>
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