Second compilation of same sources produces different set of gwt.rpc files

Question

I would like to follow up on this question gwt-serialization-policy-hosted-mode-out-of-sync. In short - when I do a RPC from hosted browser then this call fails on server with the exception.

    INFO: GwtRpcEventSrvc: ERROR: The serialization policy file '/84EC7BA65AF8175BAA99B47877FDE163.gwt.rpc' was not found; did you forget to include it in this deployment?
    SEVERE: GwtRpcEventSrvc: WARNING: Failed to get the SerializationPolicy '84EC7BA65AF8175BAA99B47877FDE163' for module 'http://host:19980/MYAPP/'; a legacy, 1.3.3 compatible, serialization policy will be used.  Youmay experience SerializationExceptions as a result.
    SEVERE: Exception while dispatching incoming RPC call

While when I do the same RPC from browser then the request is performed successfully on server.

In addition I observed a strange behavior of GWT compiler that could result in a problem with hosted browser mode.

I assume when I do two subsequent compilations of an exact same code then the result of the individual compilations is supposed to be same. I mean at least the xxxxx.html and yyyyy.gwt.rpc files have to be same. (Where xxxxx and yyyyy are the long numbers such as 84EC7BA65AF8175BAA99B47877FDE163.)

Currently I have two versions of my project.

An old project compiled by GWT 1.7 that does not suffer from problem with the hosted browser described in gwt-serialization-policy-hosted-mode-out-of-sync
A new project that is compiled by GWT 2.0.4. This new project is based on the old project. This project suffer from the hosted browser problem.

Case 1: Old project with GWT 1.7

I took my old project that was compiled by GWT 1.7. I did two compilations and I compared compilation artifacts. gwt.rpc files were same while html files had different content and name. Since the gwt.rpc files were alwas same I did not have a problem with hosted browser.

Case 2: New project with GWT 2.0.4

I compiled it twice and both gwt.rpc and html files were different. Therefore RPC call in hosted browser failed on server because of missing gwt.rpc file.

Case 3: Old project with GWT 2.0.4

I compiled it twice and both gwt.rpc and html files were different. Therefore RPC call in hosted browser failed on server because of missing gwt.rpc file.

I did some investigation and identified that when I comment out a data member in a class Data that is transmitted from server to client, then compiled files start being same.

    class Data implements IsSerializable {
           List<IsSerializable> data;
           ...
    }

I wanted to do same thing in the new project but it seems that there are many classes to be modified. So the problem is growing as the project is growing.
I don't know what to use instead of
```
List<IsSerializable> data;
```
to transfer data.

score 0 · Answer 1 · answered Nov 25 '11 at 23:15

You need to read some more on GWT serialization policies:

Serializable Types

Usually you don't mingle with .rpc files unless your are doing advanced RPC calls directly to your server.

Your serializable object :

class Data implements IsSerializable {
      List<IsSerializable> data;
       ...
}

A user-defined class is serializable if all of the following apply: It is assignable to IsSerializable or Serializable, either because it directly implements one of these interfaces or because it derives from a superclass that does All non-final, non-transient instance fields are themselves serializable, and As of GWT 1.5, it must have a default (zero argument) constructor (with any access modifier) or no constructor at all.

So you should probably have something like:

class Data implements IsSerializable {
      List<YOUR_TYPE> data;
       ...
}

Your list's template is a type, you don't set 'IsSerializable'... it should be something like :

List<int> data;

Second compilation of same sources produces different set of gwt.rpc files

1 Answers1