i am building a GWT project, with GWT-2.0.3 and eclipse plugin. well, first i tried, JSTL1.2 and servlet 2.5,
I get this error too.
I've found I can fix it by moving the GWT SDK to the bottom of the classpath in the Eclipse Java Build Path -> Order and Export dialog.
However, that breaks GWT serialization with this message:
Mar 3, 2011 3:31:23 PM sun.reflect.NativeMethodAccessorImpl invoke0
WARNING: Exception while dispatching incoming RPC call
com.google.gwt.user.client.rpc.SerializationException: java.lang.reflect.InvocationTargetException
at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeWithCustomSerializer(ServerSerializationStreamWriter.java:764)
at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serializeImpl(ServerSerializationStreamWriter.java:727)
You can fix that by moving the GWT library back up the classpath, which makes it appear like you can either have JSTL or GWT Serialization working in Jetty, but not both.
(GWT 2.1, JSTL1.2 and servlet 2.5.)