From a156f67804f5a55cc1673ed298cec4f8defd534c Mon Sep 17 00:00:00 2001
From: Trustin Lee <trustin@gmail.com>
Date: Sun, 23 Sep 2012 17:01:31 +0900
Subject: [PATCH] [#624] Add varargs constructor to MessageToByteEncoder,
 MessageToMessage(Encoder|Decoder|Codec) to implement default
 isEncodable/isDecodable()

.. and modify all their subtypes to take advantage of this improvement.
---
 .../codec/http/HttpChunkAggregator.java       |  7 +---
 .../codec/http/HttpContentDecoder.java        |  6 +--
 .../codec/http/HttpContentEncoder.java        | 13 ++-----
 .../codec/http/HttpMessageEncoder.java        |  6 +--
 .../websocketx/WebSocket00FrameEncoder.java   |  5 +--
 .../websocketx/WebSocket08FrameEncoder.java   |  9 ++---
 .../handler/codec/spdy/SpdyFrameEncoder.java  |  7 +---
 .../handler/codec/spdy/SpdyHttpDecoder.java   |  2 +
 .../handler/codec/spdy/SpdyHttpEncoder.java   |  9 +----
 .../codec/spdy/SpdySessionHandler.java        | 14 +------
 .../io/netty/handler/codec/CodecUtil.java     | 37 +++++++++++++++++++
 .../handler/codec/LengthFieldPrepender.java   |  7 +---
 .../handler/codec/MessageToByteEncoder.java   |  8 +++-
 .../handler/codec/MessageToMessageCodec.java  | 17 ++++++++-
 .../codec/MessageToMessageDecoder.java        |  8 +++-
 .../codec/MessageToMessageEncoder.java        |  8 +++-
 .../handler/codec/base64/Base64Decoder.java   |  7 +---
 .../handler/codec/base64/Base64Encoder.java   |  7 +---
 .../handler/codec/bytes/ByteArrayDecoder.java |  5 +--
 .../handler/codec/bytes/ByteArrayEncoder.java |  9 ++---
 .../codec/protobuf/ProtobufDecoder.java       |  7 +---
 .../codec/protobuf/ProtobufEncoder.java       |  5 +--
 .../ProtobufVarint32LengthFieldPrepender.java |  6 +--
 .../CompatibleObjectEncoder.java              |  7 +---
 .../codec/serialization/ObjectEncoder.java    |  5 +--
 .../handler/codec/string/StringDecoder.java   |  7 +---
 .../handler/codec/string/StringEncoder.java   | 11 ++----
 .../example/factorial/NumberEncoder.java      |  4 ++
 28 files changed, 123 insertions(+), 120 deletions(-)

diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/HttpChunkAggregator.java b/codec-http/src/main/java/io/netty/handler/codec/http/HttpChunkAggregator.java
index e175ffcdb9..c61bcd2ebb 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/HttpChunkAggregator.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/HttpChunkAggregator.java
@@ -66,6 +66,8 @@ public class HttpChunkAggregator extends MessageToMessageDecoder<Object, HttpMes
      *        a {@link TooLongFrameException} will be raised.
      */
     public HttpChunkAggregator(int maxContentLength) {
+        super(HttpMessage.class, HttpChunk.class);
+
         if (maxContentLength <= 0) {
             throw new IllegalArgumentException(
                     "maxContentLength must be a positive integer: " +
@@ -106,11 +108,6 @@ public class HttpChunkAggregator extends MessageToMessageDecoder<Object, HttpMes
         }
     }
 
-    @Override
-    public boolean isDecodable(Object msg) throws Exception {
-        return msg instanceof HttpMessage || msg instanceof HttpChunk;
-    }
-
     @Override
     public HttpMessage decode(ChannelHandlerContext ctx, Object msg) throws Exception {
         HttpMessage currentMessage = this.currentMessage;
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/HttpContentDecoder.java b/codec-http/src/main/java/io/netty/handler/codec/http/HttpContentDecoder.java
index 8fd72e51b5..1076540175 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/HttpContentDecoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/HttpContentDecoder.java
@@ -48,11 +48,7 @@ public abstract class HttpContentDecoder extends MessageToMessageDecoder<Object,
      * Creates a new instance.
      */
     protected HttpContentDecoder() {
-    }
-
-    @Override
-    public boolean isDecodable(Object msg) throws Exception {
-        return msg instanceof HttpMessage || msg instanceof HttpChunk;
+        super(HttpMessage.class, HttpChunk.class);
     }
 
     @Override
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/HttpContentEncoder.java b/codec-http/src/main/java/io/netty/handler/codec/http/HttpContentEncoder.java
index 7b78b18e6f..b0c86e5937 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/HttpContentEncoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/HttpContentEncoder.java
@@ -55,11 +55,9 @@ public abstract class HttpContentEncoder extends MessageToMessageCodec<HttpMessa
      * Creates a new instance.
      */
     protected HttpContentEncoder() {
-    }
-
-    @Override
-    public boolean isDecodable(Object msg) throws Exception {
-        return msg instanceof HttpMessage;
+        super(
+                new Class<?>[] { HttpMessage.class },
+                new Class<?>[] { HttpMessage.class, HttpChunk.class });
     }
 
     @Override
@@ -74,11 +72,6 @@ public abstract class HttpContentEncoder extends MessageToMessageCodec<HttpMessa
         return msg;
     }
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof HttpMessage || msg instanceof HttpChunk;
-    }
-
     @Override
     public Object encode(ChannelHandlerContext ctx, Object msg)
             throws Exception {
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/HttpMessageEncoder.java b/codec-http/src/main/java/io/netty/handler/codec/http/HttpMessageEncoder.java
index 8772baf1a3..b984120fbe 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/HttpMessageEncoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/HttpMessageEncoder.java
@@ -50,11 +50,7 @@ public abstract class HttpMessageEncoder extends MessageToByteEncoder<Object> {
      * Creates a new instance.
      */
     protected HttpMessageEncoder() {
-    }
-
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof HttpMessage || msg instanceof HttpChunk;
+        super(HttpMessage.class, HttpChunk.class);
     }
 
     @Override
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket00FrameEncoder.java b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket00FrameEncoder.java
index 81d5cd1686..431d40c372 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket00FrameEncoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket00FrameEncoder.java
@@ -32,9 +32,8 @@ import io.netty.handler.codec.MessageToByteEncoder;
 @Sharable
 public class WebSocket00FrameEncoder extends MessageToByteEncoder<WebSocketFrame> {
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof WebSocketFrame;
+    public WebSocket00FrameEncoder() {
+        super(WebSocketFrame.class);
     }
 
     @Override
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameEncoder.java b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameEncoder.java
index 1d77385229..937035b447 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameEncoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameEncoder.java
@@ -90,17 +90,14 @@ public class WebSocket08FrameEncoder extends MessageToByteEncoder<WebSocketFrame
      *            false.
      */
     public WebSocket08FrameEncoder(boolean maskPayload) {
+        super(WebSocketFrame.class);
         this.maskPayload = maskPayload;
     }
 
     @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof WebSocketFrame;
-    }
+    public void encode(
+            ChannelHandlerContext ctx, WebSocketFrame msg, ByteBuf out) throws Exception {
 
-    @Override
-    public void encode(ChannelHandlerContext ctx,
-            WebSocketFrame msg, ByteBuf out) throws Exception {
         byte[] mask;
 
         ByteBuf data = msg.getBinaryData();
diff --git a/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyFrameEncoder.java b/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyFrameEncoder.java
index f05b4c469a..0bc9c54bb0 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyFrameEncoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyFrameEncoder.java
@@ -49,6 +49,8 @@ public class SpdyFrameEncoder extends MessageToByteEncoder<Object> {
      * Creates a new instance with the specified parameters.
      */
     public SpdyFrameEncoder(int version, int compressionLevel, int windowBits, int memLevel) {
+        super(SpdyDataFrame.class, SpdyControlFrame.class);
+
         if (version < SpdyConstants.SPDY_MIN_VERSION || version > SpdyConstants.SPDY_MAX_VERSION) {
             throw new IllegalArgumentException(
                     "unknown version: " + version);
@@ -74,11 +76,6 @@ public class SpdyFrameEncoder extends MessageToByteEncoder<Object> {
         });
     }
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof SpdyDataFrame || msg instanceof SpdyControlFrame;
-    }
-
     @Override
     public void encode(ChannelHandlerContext ctx, Object msg, ByteBuf out) throws Exception {
         if (msg instanceof SpdyDataFrame) {
diff --git a/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHttpDecoder.java b/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHttpDecoder.java
index be61fc7ee1..d72aaf6cce 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHttpDecoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHttpDecoder.java
@@ -52,6 +52,8 @@ public class SpdyHttpDecoder extends MessageToMessageDecoder<Object, HttpMessage
      *        a {@link TooLongFrameException} will be raised.
      */
     public SpdyHttpDecoder(int version, int maxContentLength) {
+        super(SpdyDataFrame.class, SpdyControlFrame.class);
+
         if (version < SpdyConstants.SPDY_MIN_VERSION || version > SpdyConstants.SPDY_MAX_VERSION) {
             throw new IllegalArgumentException(
                     "unsupported version: " + version);
diff --git a/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHttpEncoder.java b/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHttpEncoder.java
index c413c09cbf..5ea2067883 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHttpEncoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHttpEncoder.java
@@ -129,6 +129,8 @@ public class SpdyHttpEncoder extends MessageToMessageEncoder<Object, Object> {
      * @param version the protocol version
      */
     public SpdyHttpEncoder(int version) {
+        super(HttpMessage.class, HttpChunk.class);
+
         if (version < SpdyConstants.SPDY_MIN_VERSION || version > SpdyConstants.SPDY_MAX_VERSION) {
             throw new IllegalArgumentException(
                     "unsupported version: " + version);
@@ -136,13 +138,6 @@ public class SpdyHttpEncoder extends MessageToMessageEncoder<Object, Object> {
         spdyVersion = version;
     }
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof HttpRequest ||
-                msg instanceof HttpResponse ||
-                msg instanceof HttpChunk;
-    }
-
     @Override
     public Object encode(ChannelHandlerContext ctx, Object msg) throws Exception {
 
diff --git a/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdySessionHandler.java b/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdySessionHandler.java
index 145c987601..57d8d969f2 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdySessionHandler.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/spdy/SpdySessionHandler.java
@@ -103,19 +103,7 @@ public class SpdySessionHandler
                 break;
             }
 
-            if (msg instanceof SpdyDataFrame ||
-                    msg instanceof SpdySynStreamFrame ||
-                    msg instanceof SpdySynReplyFrame ||
-                    msg instanceof SpdyRstStreamFrame ||
-                    msg instanceof SpdySettingsFrame ||
-                    msg instanceof SpdyPingFrame ||
-                    msg instanceof SpdyGoAwayFrame ||
-                    msg instanceof SpdyHeadersFrame ||
-                    msg instanceof SpdyWindowUpdateFrame) {
-                handleInboundMessage(ctx, msg);
-            } else {
-                ctx.nextInboundMessageBuffer().add(msg);
-            }
+            handleInboundMessage(ctx, msg);
         }
         ctx.fireInboundBufferUpdated();
     }
diff --git a/codec/src/main/java/io/netty/handler/codec/CodecUtil.java b/codec/src/main/java/io/netty/handler/codec/CodecUtil.java
index 43d8c76723..de26a0e266 100644
--- a/codec/src/main/java/io/netty/handler/codec/CodecUtil.java
+++ b/codec/src/main/java/io/netty/handler/codec/CodecUtil.java
@@ -82,6 +82,43 @@ final class CodecUtil {
                 msg.getClass().getSimpleName()));
     }
 
+    private static final Class<?>[] EMPTY_TYPES = new Class<?>[0];
+
+    static Class<?>[] acceptedMessageTypes(Class<?>[] acceptedMsgTypes) {
+        if (acceptedMsgTypes == null) {
+            return EMPTY_TYPES;
+        }
+
+        int numElem = 0;
+        for (Class<?> c: acceptedMsgTypes) {
+            if (c == null) {
+                break;
+            }
+            numElem ++;
+        }
+
+        Class<?>[] newAllowedMsgTypes = new Class[numElem];
+        for (int i = 0; i < numElem; i ++) {
+            newAllowedMsgTypes[i] = acceptedMsgTypes[i];
+        }
+
+        return newAllowedMsgTypes;
+    }
+
+    static boolean acceptMessage(Class<?>[] acceptedMsgTypes, Object msg) {
+        if (acceptedMsgTypes.length == 0) {
+            return true;
+        }
+
+        for (Class<?> c: acceptedMsgTypes) {
+            if (c.isInstance(msg)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     private CodecUtil() {
         // Unused
     }
diff --git a/codec/src/main/java/io/netty/handler/codec/LengthFieldPrepender.java b/codec/src/main/java/io/netty/handler/codec/LengthFieldPrepender.java
index 46763ea5f4..83cceab485 100644
--- a/codec/src/main/java/io/netty/handler/codec/LengthFieldPrepender.java
+++ b/codec/src/main/java/io/netty/handler/codec/LengthFieldPrepender.java
@@ -83,6 +83,8 @@ public class LengthFieldPrepender extends MessageToByteEncoder<ByteBuf> {
      */
     public LengthFieldPrepender(
             int lengthFieldLength, boolean lengthIncludesLengthFieldLength) {
+        super(ByteBuf.class);
+
         if (lengthFieldLength != 1 && lengthFieldLength != 2 &&
             lengthFieldLength != 3 && lengthFieldLength != 4 &&
             lengthFieldLength != 8) {
@@ -95,11 +97,6 @@ public class LengthFieldPrepender extends MessageToByteEncoder<ByteBuf> {
         this.lengthIncludesLengthFieldLength = lengthIncludesLengthFieldLength;
     }
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof ByteBuf;
-    }
-
     @Override
     public void encode(
             ChannelHandlerContext ctx,
diff --git a/codec/src/main/java/io/netty/handler/codec/MessageToByteEncoder.java b/codec/src/main/java/io/netty/handler/codec/MessageToByteEncoder.java
index 567ac9f0b7..92b0536485 100644
--- a/codec/src/main/java/io/netty/handler/codec/MessageToByteEncoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/MessageToByteEncoder.java
@@ -23,6 +23,12 @@ import io.netty.channel.ChannelOutboundMessageHandlerAdapter;
 
 public abstract class MessageToByteEncoder<I> extends ChannelOutboundMessageHandlerAdapter<I> {
 
+    private final Class<?>[] acceptedMsgTypes;
+
+    protected MessageToByteEncoder(Class<?>... acceptedMsgTypes) {
+        this.acceptedMsgTypes = CodecUtil.acceptedMessageTypes(acceptedMsgTypes);
+    }
+
     @Override
     public void flush(ChannelHandlerContext ctx, ChannelFuture future) throws Exception {
         MessageBuf<I> in = ctx.outboundMessageBuffer();
@@ -61,7 +67,7 @@ public abstract class MessageToByteEncoder<I> extends ChannelOutboundMessageHand
      * @param msg the message
      */
     public boolean isEncodable(Object msg) throws Exception {
-        return true;
+        return CodecUtil.acceptMessage(acceptedMsgTypes, msg);
     }
 
     public abstract void encode(ChannelHandlerContext ctx, I msg, ByteBuf out) throws Exception;
diff --git a/codec/src/main/java/io/netty/handler/codec/MessageToMessageCodec.java b/codec/src/main/java/io/netty/handler/codec/MessageToMessageCodec.java
index 8ff57491bb..d86e6c5cfe 100644
--- a/codec/src/main/java/io/netty/handler/codec/MessageToMessageCodec.java
+++ b/codec/src/main/java/io/netty/handler/codec/MessageToMessageCodec.java
@@ -53,6 +53,19 @@ public abstract class MessageToMessageCodec<INBOUND_IN, INBOUND_OUT, OUTBOUND_IN
         }
     };
 
+    private final Class<?>[] acceptedInboundMsgTypes;
+    private final Class<?>[] acceptedOutboundMsgTypes;
+
+    protected MessageToMessageCodec() {
+        this(null, null);
+    }
+
+    protected MessageToMessageCodec(
+            Class<?>[] acceptedInboundMsgTypes, Class<?>[] acceptedOutboundMsgTypes) {
+        this.acceptedInboundMsgTypes = CodecUtil.acceptedMessageTypes(acceptedInboundMsgTypes);
+        this.acceptedOutboundMsgTypes = CodecUtil.acceptedMessageTypes(acceptedOutboundMsgTypes);
+    }
+
     @Override
     public MessageBuf<INBOUND_IN> newInboundBuffer(ChannelHandlerContext ctx) throws Exception {
         return decoder.newInboundBuffer(ctx);
@@ -80,7 +93,7 @@ public abstract class MessageToMessageCodec<INBOUND_IN, INBOUND_OUT, OUTBOUND_IN
      * @param msg the message
      */
     public boolean isDecodable(Object msg) throws Exception {
-        return true;
+        return CodecUtil.acceptMessage(acceptedInboundMsgTypes, msg);
     }
 
     /**
@@ -89,7 +102,7 @@ public abstract class MessageToMessageCodec<INBOUND_IN, INBOUND_OUT, OUTBOUND_IN
      * @param msg the message
      */
     public boolean isEncodable(Object msg) throws Exception {
-        return true;
+        return CodecUtil.acceptMessage(acceptedOutboundMsgTypes, msg);
     }
 
     public abstract OUTBOUND_OUT encode(ChannelHandlerContext ctx, OUTBOUND_IN msg) throws Exception;
diff --git a/codec/src/main/java/io/netty/handler/codec/MessageToMessageDecoder.java b/codec/src/main/java/io/netty/handler/codec/MessageToMessageDecoder.java
index a2caf625ba..650939d237 100644
--- a/codec/src/main/java/io/netty/handler/codec/MessageToMessageDecoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/MessageToMessageDecoder.java
@@ -24,6 +24,12 @@ import io.netty.channel.ChannelInboundMessageHandler;
 public abstract class MessageToMessageDecoder<I, O>
         extends ChannelInboundHandlerAdapter implements ChannelInboundMessageHandler<I> {
 
+    private final Class<?>[] acceptedMsgTypes;
+
+    protected MessageToMessageDecoder(Class<?>... acceptedMsgTypes) {
+        this.acceptedMsgTypes = CodecUtil.acceptedMessageTypes(acceptedMsgTypes);
+    }
+
     @Override
     public MessageBuf<I> newInboundBuffer(ChannelHandlerContext ctx) throws Exception {
         return Unpooled.messageBuffer();
@@ -77,7 +83,7 @@ public abstract class MessageToMessageDecoder<I, O>
      * @param msg the message
      */
     public boolean isDecodable(Object msg) throws Exception {
-        return true;
+        return CodecUtil.acceptMessage(acceptedMsgTypes, msg);
     }
 
     public abstract O decode(ChannelHandlerContext ctx, I msg) throws Exception;
diff --git a/codec/src/main/java/io/netty/handler/codec/MessageToMessageEncoder.java b/codec/src/main/java/io/netty/handler/codec/MessageToMessageEncoder.java
index 3b22fc6c3d..cbc0be41ee 100644
--- a/codec/src/main/java/io/netty/handler/codec/MessageToMessageEncoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/MessageToMessageEncoder.java
@@ -22,6 +22,12 @@ import io.netty.channel.ChannelOutboundMessageHandlerAdapter;
 
 public abstract class MessageToMessageEncoder<I, O> extends ChannelOutboundMessageHandlerAdapter<I> {
 
+    private final Class<?>[] acceptedMsgTypes;
+
+    protected MessageToMessageEncoder(Class<?>... acceptedMsgTypes) {
+        this.acceptedMsgTypes = CodecUtil.acceptedMessageTypes(acceptedMsgTypes);
+    }
+
     @Override
     public void flush(ChannelHandlerContext ctx, ChannelFuture future) throws Exception {
         MessageBuf<I> in = ctx.outboundMessageBuffer();
@@ -65,7 +71,7 @@ public abstract class MessageToMessageEncoder<I, O> extends ChannelOutboundMessa
      * @param msg the message
      */
     public boolean isEncodable(Object msg) throws Exception {
-        return true;
+        return CodecUtil.acceptMessage(acceptedMsgTypes, msg);
     }
 
     public abstract O encode(ChannelHandlerContext ctx, I msg) throws Exception;
diff --git a/codec/src/main/java/io/netty/handler/codec/base64/Base64Decoder.java b/codec/src/main/java/io/netty/handler/codec/base64/Base64Decoder.java
index 985bcfdc12..e820483a4d 100644
--- a/codec/src/main/java/io/netty/handler/codec/base64/Base64Decoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/base64/Base64Decoder.java
@@ -53,17 +53,14 @@ public class Base64Decoder extends MessageToMessageDecoder<ByteBuf, ByteBuf> {
     }
 
     public Base64Decoder(Base64Dialect dialect) {
+        super(ByteBuf.class);
+
         if (dialect == null) {
             throw new NullPointerException("dialect");
         }
         this.dialect = dialect;
     }
 
-    @Override
-    public boolean isDecodable(Object msg) throws Exception {
-        return msg instanceof ByteBuf;
-    }
-
     @Override
     public ByteBuf decode(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
         return Base64.decode(msg, msg.readerIndex(), msg.readableBytes(), dialect);
diff --git a/codec/src/main/java/io/netty/handler/codec/base64/Base64Encoder.java b/codec/src/main/java/io/netty/handler/codec/base64/Base64Encoder.java
index c90790f745..8d95fc9fba 100644
--- a/codec/src/main/java/io/netty/handler/codec/base64/Base64Encoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/base64/Base64Encoder.java
@@ -54,6 +54,8 @@ public class Base64Encoder extends MessageToMessageEncoder<ByteBuf, ByteBuf> {
     }
 
     public Base64Encoder(boolean breakLines, Base64Dialect dialect) {
+        super(ByteBuf.class);
+
         if (dialect == null) {
             throw new NullPointerException("dialect");
         }
@@ -62,11 +64,6 @@ public class Base64Encoder extends MessageToMessageEncoder<ByteBuf, ByteBuf> {
         this.dialect = dialect;
     }
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof ByteBuf;
-    }
-
     @Override
     public ByteBuf encode(ChannelHandlerContext ctx,
             ByteBuf msg) throws Exception {
diff --git a/codec/src/main/java/io/netty/handler/codec/bytes/ByteArrayDecoder.java b/codec/src/main/java/io/netty/handler/codec/bytes/ByteArrayDecoder.java
index 50f00a99b2..300dabe263 100644
--- a/codec/src/main/java/io/netty/handler/codec/bytes/ByteArrayDecoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/bytes/ByteArrayDecoder.java
@@ -49,9 +49,8 @@ import io.netty.handler.codec.MessageToMessageDecoder;
  */
 public class ByteArrayDecoder extends MessageToMessageDecoder<ByteBuf, byte[]> {
 
-    @Override
-    public boolean isDecodable(Object msg) throws Exception {
-        return msg instanceof ByteBuf;
+    public ByteArrayDecoder() {
+        super(ByteBuf.class);
     }
 
     @Override
diff --git a/codec/src/main/java/io/netty/handler/codec/bytes/ByteArrayEncoder.java b/codec/src/main/java/io/netty/handler/codec/bytes/ByteArrayEncoder.java
index 93e91567ec..87eb79112a 100644
--- a/codec/src/main/java/io/netty/handler/codec/bytes/ByteArrayEncoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/bytes/ByteArrayEncoder.java
@@ -51,14 +51,13 @@ import io.netty.handler.codec.MessageToMessageEncoder;
  */
 public class ByteArrayEncoder extends MessageToMessageEncoder<byte[], ByteBuf> {
 
-    @Override
-    public MessageBuf<byte[]> newOutboundBuffer(ChannelHandlerContext ctx) throws Exception {
-        return Unpooled.messageBuffer();
+    public ByteArrayEncoder() {
+        super(byte[].class);
     }
 
     @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof byte[];
+    public MessageBuf<byte[]> newOutboundBuffer(ChannelHandlerContext ctx) throws Exception {
+        return Unpooled.messageBuffer();
     }
 
     @Override
diff --git a/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufDecoder.java b/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufDecoder.java
index 77b940e992..3320fc432e 100644
--- a/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufDecoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufDecoder.java
@@ -74,6 +74,8 @@ public class ProtobufDecoder extends MessageToMessageDecoder<ByteBuf, MessageLit
     }
 
     public ProtobufDecoder(MessageLite prototype, ExtensionRegistry extensionRegistry) {
+        super(ByteBuf.class);
+
         if (prototype == null) {
             throw new NullPointerException("prototype");
         }
@@ -81,11 +83,6 @@ public class ProtobufDecoder extends MessageToMessageDecoder<ByteBuf, MessageLit
         this.extensionRegistry = extensionRegistry;
     }
 
-    @Override
-    public boolean isDecodable(Object msg) throws Exception {
-        return msg instanceof ByteBuf;
-    }
-
     @Override
     public MessageLite decode(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
         if (msg.hasArray()) {
diff --git a/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufEncoder.java b/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufEncoder.java
index 75b97d59cf..a5cdfece63 100644
--- a/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufEncoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufEncoder.java
@@ -59,9 +59,8 @@ import com.google.protobuf.MessageLite;
 @Sharable
 public class ProtobufEncoder extends MessageToMessageEncoder<Object, ByteBuf> {
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof MessageLite || msg instanceof MessageLite.Builder;
+    public ProtobufEncoder() {
+        super(MessageLite.class, MessageLite.Builder.class);
     }
 
     @Override
diff --git a/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufVarint32LengthFieldPrepender.java b/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufVarint32LengthFieldPrepender.java
index 98ecb47113..0a5c89f120 100644
--- a/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufVarint32LengthFieldPrepender.java
+++ b/codec/src/main/java/io/netty/handler/codec/protobuf/ProtobufVarint32LengthFieldPrepender.java
@@ -44,11 +44,7 @@ public class ProtobufVarint32LengthFieldPrepender extends MessageToByteEncoder<B
      * Creates a new instance.
      */
     public ProtobufVarint32LengthFieldPrepender() {
-    }
-
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof ByteBuf;
+        super(ByteBuf.class);
     }
 
     @Override
diff --git a/codec/src/main/java/io/netty/handler/codec/serialization/CompatibleObjectEncoder.java b/codec/src/main/java/io/netty/handler/codec/serialization/CompatibleObjectEncoder.java
index 519a135d59..f44dc046bc 100644
--- a/codec/src/main/java/io/netty/handler/codec/serialization/CompatibleObjectEncoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/serialization/CompatibleObjectEncoder.java
@@ -59,6 +59,8 @@ public class CompatibleObjectEncoder extends MessageToByteEncoder<Object> {
      *        the long term.
      */
     public CompatibleObjectEncoder(int resetInterval) {
+        super(Serializable.class);
+
         if (resetInterval < 0) {
             throw new IllegalArgumentException(
                     "resetInterval: " + resetInterval);
@@ -75,11 +77,6 @@ public class CompatibleObjectEncoder extends MessageToByteEncoder<Object> {
         return new ObjectOutputStream(out);
     }
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof Serializable;
-    }
-
     @Override
     public void encode(ChannelHandlerContext ctx, Object msg, ByteBuf out) throws Exception {
         Attribute<ObjectOutputStream> oosAttr = ctx.attr(OOS);
diff --git a/codec/src/main/java/io/netty/handler/codec/serialization/ObjectEncoder.java b/codec/src/main/java/io/netty/handler/codec/serialization/ObjectEncoder.java
index 9205635990..96e620d622 100644
--- a/codec/src/main/java/io/netty/handler/codec/serialization/ObjectEncoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/serialization/ObjectEncoder.java
@@ -39,9 +39,8 @@ import java.io.Serializable;
 public class ObjectEncoder extends MessageToByteEncoder<Object> {
     private static final byte[] LENGTH_PLACEHOLDER = new byte[4];
 
-    @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof Serializable;
+    public ObjectEncoder() {
+        super(Serializable.class);
     }
 
     @Override
diff --git a/codec/src/main/java/io/netty/handler/codec/string/StringDecoder.java b/codec/src/main/java/io/netty/handler/codec/string/StringDecoder.java
index f8528cdac5..6e955f3e12 100644
--- a/codec/src/main/java/io/netty/handler/codec/string/StringDecoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/string/StringDecoder.java
@@ -68,17 +68,14 @@ public class StringDecoder extends MessageToMessageDecoder<ByteBuf, String> {
      * Creates a new instance with the specified character set.
      */
     public StringDecoder(Charset charset) {
+        super(ByteBuf.class);
+
         if (charset == null) {
             throw new NullPointerException("charset");
         }
         this.charset = charset;
     }
 
-    @Override
-    public boolean isDecodable(Object msg) throws Exception {
-        return msg instanceof ByteBuf;
-    }
-
     @Override
     public String decode(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
         return msg.toString(charset);
diff --git a/codec/src/main/java/io/netty/handler/codec/string/StringEncoder.java b/codec/src/main/java/io/netty/handler/codec/string/StringEncoder.java
index 795c6b46b4..91faa5c029 100644
--- a/codec/src/main/java/io/netty/handler/codec/string/StringEncoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/string/StringEncoder.java
@@ -50,7 +50,7 @@ import java.nio.charset.Charset;
  * @apiviz.landmark
  */
 @Sharable
-public class StringEncoder extends MessageToMessageEncoder<String, ByteBuf> {
+public class StringEncoder extends MessageToMessageEncoder<CharSequence, ByteBuf> {
 
     // TODO Use CharsetEncoder instead.
     private final Charset charset;
@@ -66,6 +66,8 @@ public class StringEncoder extends MessageToMessageEncoder<String, ByteBuf> {
      * Creates a new instance with the specified character set.
      */
     public StringEncoder(Charset charset) {
+        super(CharSequence.class);
+
         if (charset == null) {
             throw new NullPointerException("charset");
         }
@@ -73,12 +75,7 @@ public class StringEncoder extends MessageToMessageEncoder<String, ByteBuf> {
     }
 
     @Override
-    public boolean isEncodable(Object msg) throws Exception {
-        return msg instanceof String;
-    }
-
-    @Override
-    public ByteBuf encode(ChannelHandlerContext ctx, String msg) throws Exception {
+    public ByteBuf encode(ChannelHandlerContext ctx, CharSequence msg) throws Exception {
         return Unpooled.copiedBuffer(msg, charset);
     }
 }
diff --git a/example/src/main/java/io/netty/example/factorial/NumberEncoder.java b/example/src/main/java/io/netty/example/factorial/NumberEncoder.java
index 4fcd80adbc..ebe79f3e9e 100644
--- a/example/src/main/java/io/netty/example/factorial/NumberEncoder.java
+++ b/example/src/main/java/io/netty/example/factorial/NumberEncoder.java
@@ -28,6 +28,10 @@ import java.math.BigInteger;
  */
 public class NumberEncoder extends MessageToByteEncoder<Number> {
 
+    public NumberEncoder() {
+        super(Number.class);
+    }
+
     @Override
     public void encode(
             ChannelHandlerContext ctx, Number msg, ByteBuf out) throws Exception {