diff --git a/src/main/java/org/jboss/netty/handler/codec/replay/ReplayingDecoder.java b/src/main/java/org/jboss/netty/handler/codec/replay/ReplayingDecoder.java index 128d27f9fd..c3dd2ab5f2 100644 --- a/src/main/java/org/jboss/netty/handler/codec/replay/ReplayingDecoder.java +++ b/src/main/java/org/jboss/netty/handler/codec/replay/ReplayingDecoder.java @@ -118,6 +118,48 @@ import org.jboss.netty.handler.codec.frame.FrameDecoder; * format is complicated unlike the example above. In this case, your * decoder might have to decode the same part of the message over and over * again. + *
  • You must keep in mind that {@code decode(..)} method can be called many + * times to decode a single message. For example, the following code will + * not work: + *
    public class MyDecoder extends ReplayingDecoder<VoidEnum> {
    + *
    + *     private final Queue<Integer> values = new LinkedList<Integer>();
    + *
    + *     public Object decode(.., ChannelBuffer buffer, ..) throws Exception {
    + *
    + *         // A message contains 2 integers.
    + *         values.offer(buffer.readInt());
    + *         values.offer(buffer.readInt());
    + *
    + *         // This assertion will fail intermittently since values.offer()
    + *         // can be called more than two times!
    + *         assert values.size() == 2;
    + *         return values.poll() + values.poll();
    + *     }
    + * }
    + * The correct implementation looks like the following, and you can utilize + * the 'checkpoint' feature which is explained in detail in the next + * section. + *
    public class MyDecoder extends ReplayingDecoder<VoidEnum> {
    + *
    + *     private final Queue<Integer> values = new LinkedList<Integer>();
    + *
    + *     public Object decode(.., ChannelBuffer buffer, ..) throws Exception {
    + *
    + *         // Revert the state of the variable that might have been changed
    + *         // since the last partial decode.
    + *         values.clear();
    + *
    + *         // A message contains 2 integers.
    + *         values.offer(buffer.readInt());
    + *         values.offer(buffer.readInt());
    + *
    + *         // Now we know this assertion will never fail.
    + *         assert values.size() == 2;
    + *         return values.poll() + values.poll();
    + *     }
    + * }
    + *
  • * * *

    Improving the performance