Question

I have an application using gwt and hosted on gae. There is a form using xfbml and having a redirect url once data is filled and form is submit. the problem is it throws exception if this happens via xfbml form submit. if i invoke the url directly it works great.

The xfbml code is:

<fb:registration redirect-uri="http://www.sakshum.org/FbBloodDonorRegister" fields='[{"name":"name"},{"name":"first_name"},{"name":"last_name"}, {"name":"cellPhone", "description":"Cell Number", "type":"text"}, {"name":"homePhone", "description":"Home Number", "type":"text"}]'  onvalidate="validated" width="530">
</fb:registration>

The exception is below

javax.servlet.ServletContext log: Exception while dispatching incoming RPC call
javax.servlet.ServletException: Content-Type was 'application/x-www-form-urlencoded'. Expected 'text/x-gwt-rpc'.
    at com.google.gwt.user.server.rpc.RPCServletUtils.checkContentTypeIgnoreCase(RPCServletUtils.java:427)
    at com.google.gwt.user.server.rpc.RPCServletUtils.readContent(RPCServletUtils.java:160)
    at com.google.gwt.user.server.rpc.RPCServletUtils.readContentAsGwtRpc(RPCServletUtils.java:205)
    at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.readContent(AbstractRemoteServiceServlet.java:182)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:239)
    at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.apphosting.utils.servlet.ParseBlobUploadFilter.doFilter(ParseBlobUploadFilter.java:102)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.runtime.jetty.SaveSessionFilter.doFilter(SaveSessionFilter.java:35)
    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 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.runtime.jetty.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:249)
    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$RequestHandler.headerComplete(HttpConnection.java:923)
    at com.google.apphosting.runtime.jetty.RpcRequestParser.parseAvailable(RpcRequestParser.java:76)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at com.google.apphosting.runtime.jetty.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:135)
    at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:447)
    at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:452)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:458)
    at com.google.tracing.TraceContext.runInContext(TraceContext.java:698)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:336)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:328)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:456)
    at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:251)
    at java.lang.Thread.run(Thread.java:679)

Answer 1

Look at this file, which is called above:
http://code.google.com/p/google-web-toolkit/source/browse/trunk/user/src/com/google/gwt/user/server/rpc/RPCServletUtils.java

You’re not going to be able to change the expected content-type easily, since that’s specified in

public static String readContentAsGwtRpc(HttpServletRequest request)
  throws IOException, ServletException {
    return readContent(request, GWT_RPC_CONTENT_TYPE, CHARSET_UTF8_NAME);
}

The key seems to be that you’re calling a RPC-specific servlet from Facebook’s XFBML. It’s not worth it to try fiddle with the RPC-specific calls and you probably can’t change how FB calls it. The simplest solution is to add another servlet that accepts normal POSTS and GETS, and just call that from Facebook.