Ensure CombinedChannelDuplexHandler can not be shared.

Motivation:

CombinedChannelDuplexHandler must not be shared as it contains state.

Modifications:

Enforce that it is not shared.

Result:

Fixes [#6333]

codec/src/main/java/io/netty/handler/codec/ByteToMessageCodec.java

@@ -70,7 +70,7 @@ public abstract class ByteToMessageCodec<I> extends ChannelDuplexHandler {
      *                              {@link ByteBuf}, which is backed by an byte array.
      */
     protected ByteToMessageCodec(boolean preferDirect) {
-        CodecUtil.ensureNotSharable(this);
+        ensureNotSharable();
         outboundMsgMatcher = TypeParameterMatcher.find(this, ByteToMessageCodec.class, "I");
         encoder = new Encoder(preferDirect);
     }
@@ -84,7 +84,7 @@ public abstract class ByteToMessageCodec<I> extends ChannelDuplexHandler {
      *                              {@link ByteBuf}, which is backed by an byte array.
      */
     protected ByteToMessageCodec(Class<? extends I> outboundMessageType, boolean preferDirect) {
-        CodecUtil.ensureNotSharable(this);
+        ensureNotSharable();
         outboundMsgMatcher = TypeParameterMatcher.get(outboundMessageType);
         encoder = new Encoder(preferDirect);
     }

codec/src/main/java/io/netty/handler/codec/ByteToMessageDecoder.java

@@ -138,7 +138,7 @@ public abstract class ByteToMessageDecoder extends ChannelInboundHandlerAdapter
     private int numReads;
 
     protected ByteToMessageDecoder() {
-        CodecUtil.ensureNotSharable(this);
+        ensureNotSharable();
     }
 
     /**

codec/src/main/java/io/netty/handler/codec/CodecUtil.java

@@ -1,32 +0,0 @@
-/*
- * Copyright 2014 The Netty Project
- *
- * The Netty Project licenses this file to you under the Apache License,
- * version 2.0 (the "License"); you may not use this file except in compliance
- * with the License. You may obtain a copy of the License at:
- *
- *   http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
- * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
- * License for the specific language governing permissions and limitations
- * under the License.
- */
-package io.netty.handler.codec;
-
-import io.netty.channel.ChannelHandlerAdapter;
-
-final class CodecUtil {
-
-    /**
-     * Throws {@link IllegalStateException} if {@link ChannelHandlerAdapter#isSharable()} returns {@code true}
-     */
-    static void ensureNotSharable(ChannelHandlerAdapter handler) {
-        if (handler.isSharable()) {
-            throw new IllegalStateException("@Sharable annotation is not allowed");
-        }
-    }
-
-    private CodecUtil() { }
-}

transport/src/main/java/io/netty/channel/ChannelHandlerAdapter.java

@@ -28,6 +28,15 @@ public abstract class ChannelHandlerAdapter implements ChannelHandler {
     // Not using volatile because it's used only for a sanity check.
     boolean added;
 
+    /**
+     * Throws {@link IllegalStateException} if {@link ChannelHandlerAdapter#isSharable()} returns {@code true}
+     */
+    protected void ensureNotSharable() {
+        if (isSharable()) {
+            throw new IllegalStateException("ChannelHandler " + getClass().getName() + " is not allowed to be shared");
+        }
+    }
+
     /**
      * Return {@code true} if the implementation is {@link Sharable} and so can be added
      * to different {@link ChannelPipeline}s.

transport/src/main/java/io/netty/channel/CombinedChannelDuplexHandler.java

@@ -45,12 +45,15 @@ public class CombinedChannelDuplexHandler<I extends ChannelInboundHandler, O ext
      * {@link #init(ChannelInboundHandler, ChannelOutboundHandler)} before adding this handler into a
      * {@link ChannelPipeline}.
      */
-    protected CombinedChannelDuplexHandler() { }
+    protected CombinedChannelDuplexHandler() {
+        ensureNotSharable();
+    }
 
     /**
      * Creates a new instance that combines the specified two handlers into one.
      */
     public CombinedChannelDuplexHandler(I inboundHandler, O outboundHandler) {
+        ensureNotSharable();
         init(inboundHandler, outboundHandler);
     }
 

transport/src/test/java/io/netty/channel/CombinedChannelDuplexHandlerTest.java

@@ -387,4 +387,14 @@ public class CombinedChannelDuplexHandlerTest {
         promise.syncUninterruptibly();
         ch.finish();
     }
+
+    @Test(expected = IllegalStateException.class)
+    public void testNotSharable() {
+        new CombinedChannelDuplexHandler<ChannelInboundHandler, ChannelOutboundHandler>() {
+            @Override
+            public boolean isSharable() {
+                return true;
+            }
+        };
+    }
 }