Reports incorrect WebSocket methods annotated with @OnMessage.

This annotation marks methods that handle incoming WebSocket messages. Each WebSocket endpoint can have only one message-handling method for every WebSocket message format: text, binary, and pong. Methods with the @OnMessage annotation are allowed to have the following set of parameters in any order:

• Exactly one of any of the following:
  • If the method is handling text messages:
    • String to receive the whole message
    • Java primitive or class equivalent to receive the whole message converted to that type
    • String and boolean pair to receive the message in parts
    • Reader to receive the whole message as a blocking stream
    • Any object parameter for which the endpoint has a text decoder (Decoder.Text or Decoder.TextStream)
  • If the method is handling binary messages:
    • byte[] or ByteBuffer to receive the whole message
    • byte[] and boolean pair, or ByteBuffer and boolean pair to receive the message in parts
    • InputStream to receive the whole message as a blocking stream
    • Any object parameter for which the endpoint has a binary decoder (Decoder.Binary or Decoder.BinaryStream)
  • If the method is handling pong messages:
    • PongMessage for handling pong messages
• Any number of String or Java primitive parameters annotated with @PathParam for server endpoints
• An optional Session parameter

If the method returns a value, the WebSocket runtime will interpret it as a message to return to the peer. The allowed return types are String, ByteBuffer, byte[], any Java primitive or class equivalent, and anything for which there is an encoder. If the method returns a Java primitive value, the implementation must construct the text message to send using the standard Java string representation of the Java primitive unless the developer provided an encoder for the type configured for this endpoint, in which case that encoder must be used. If the method returns a class equivalent of a Java primitive, the implementation must construct the text message from the Java primitive equivalent as described before.