Example of doGetSerializationPolicy implementation

servlet.java

  @Override
  protected com.google.gwt.user.server.rpc.SerializationPolicy doGetSerializationPolicy( @javax.annotation.Nonnull final javax.servlet.http.HttpServletRequest request,
                                                                                         @javax.annotation.Nonnull final String moduleBase,
                                                                                         @javax.annotation.Nonnull final String strongName )
  {
    java.net.URL moduleBaseURL = null;
    if ( null != moduleBase )
    {
      try
      {
        moduleBaseURL = new java.net.URL( moduleBase );
      }
      catch ( final java.net.MalformedURLException e )
      {
        // log the information, we will default
        log( "Malformed moduleBaseURL: " + moduleBase, e );
        return null;
      }
    }

    final String contextPath = request.getContextPath();
    java.io.InputStream stream = null;
    String path = strongName;
    if ( null != moduleBaseURL && moduleBaseURL.getPath().startsWith( contextPath ) )
    {
      final String contextRelativePath = moduleBaseURL.getPath().substring( contextPath.length() );
      path = contextRelativePath + strongName + ".gwt.rpc";
      stream = getServletContext().getResourceAsStream( path );
    }
    else if ( null != moduleBaseURL )
    {
      path = moduleBaseURL.toExternalForm() + strongName + ".gwt.rpc";
      try
      {
        stream = new java.net.URL( path ).openStream();
      }
      catch ( final java.io.IOException e )
      {
        log( "ERROR: Failed to read the remote policy file '" + path + "'", e );
        return null;
      }
    }
    if ( null != stream )
    {
      try ( java.io.InputStream input = stream )
      {
        return com.google.gwt.user.server.rpc.SerializationPolicyLoader.loadFromStream( input, null );
      }
      catch ( final java.text.ParseException e )
      {
        log( "ERROR: Failed to parse the policy file '" + path + "'", e );
      }
      catch ( final java.io.IOException e )
      {
        log( "ERROR: Could not read the policy file '" + path + "'", e );
      }
    }
    // If CodeServerPolicyUrl is available then we are probably in development and thus
    // the policies are not expected to be part of the deployment
    else if ( null == getCodeServerPolicyUrl( strongName ) )
    {
      final String message =
        "ERROR: The serialization policy file '" + path + "' was not found; " +
        "did you forget to include it in this deployment?";
      log( message );
    }

    return null;
  }