NPE in tomcat because of WebSocket API and Lambdas

[Steffen Heil (Mailinglisten)]

Hi


I just got the following NPE in tomcat:
 
 java.lang.NullPointerException
       at org.apache.tomcat.websocket.Util.getGenericType(Util.java:217)
       at org.apache.tomcat.websocket.Util.getMessageType(Util.java:171)
       at 
org.apache.tomcat.websocket.WsSession.addMessageHandler(WsSession.java:198)
       at ...
       at 
org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.init(WsHttpUpgradeHandler.java:138)
       at 
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:701)
       at 
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1526)
       at 
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1482)
       at 
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
       at 
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
       at 
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
       at java.lang.Thread.run(Thread.java:745)


That happened because eclipse "cleaned up" my code:

                        session.addMessageHandler( new 
MessageHandler.Whole<String>() {
                                
                                @Override
                                public void onMessage( String text )
                                {
                                        processor.received( text );
                                }
                                
                        } );
                        session.addMessageHandler( new 
MessageHandler.Whole<ByteBuffer>() {
                                
                                @Override
                                public void onMessage( ByteBuffer data )
                                {
                                        processor.received( data );
                                }
                                
                        } );

Resulting in:

                        session.addMessageHandler( (Whole<String>) text -> 
processor.received( text ) );
                        session.addMessageHandler( (Whole<ByteBuffer>) data -> 
processor.received( data ) );


So I understand that tomcat tries to get the type of the message handler using 
reflection.
While I believe this is a bad API, it's not tomcats fault. However it should 
not throw a NPE...

But I think there is no other way for the to register message handlers, right?
So do I need to stick to the anonymous classes or is there a way to make it 
work with lambdas?


Regards,
  Steffen

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