[#486] Make NoSuchBufferException give more useful message.

- Remove confusing exception messages
- Do not use default exception messages wherever possible

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

@@ -17,6 +17,8 @@ package io.netty.handler.codec;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelInboundHandler;
+import io.netty.channel.ChannelOutboundHandler;
 import io.netty.channel.NoSuchBufferException;
 
 final class CodecUtil {
@@ -72,7 +74,12 @@ final class CodecUtil {
             }
         }
 
-        throw new NoSuchBufferException();
+        throw new NoSuchBufferException(String.format(
+                "the handler '%s' could not find a %s which accepts a %s.",
+                ctx.name(),
+                inbound? ChannelInboundHandler.class.getSimpleName()
+                       : ChannelOutboundHandler.class.getSimpleName(),
+                msg.getClass().getSimpleName()));
     }
 
     private CodecUtil() {

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

@@ -44,12 +44,14 @@ public abstract class AbstractServerChannel extends AbstractChannel implements S
 
     @Override
     public ByteBuf outboundByteBuffer() {
-        throw new NoSuchBufferException();
+        throw new NoSuchBufferException(String.format(
+                "%s does not have an outbound buffer.", ServerChannel.class.getSimpleName()));
     }
 
     @Override
     public MessageBuf<Object> outboundMessageBuffer() {
-        throw new NoSuchBufferException();
+        throw new NoSuchBufferException(String.format(
+                "%s does not have an outbound buffer.", ServerChannel.class.getSimpleName()));
     }
 
     @Override

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

@@ -366,7 +366,17 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
     @Override
     public ByteBuf inboundByteBuffer() {
         if (inByteBuf == null) {
-            throw new NoSuchBufferException();
+            if (handler instanceof ChannelInboundHandler) {
+                throw new NoSuchBufferException(String.format(
+                        "the handler '%s' has no inbound byte buffer; it implements %s, but " +
+                        "its newInboundBuffer() method created a %s.",
+                        name, ChannelInboundHandler.class.getSimpleName(),
+                        MessageBuf.class.getSimpleName()));
+            } else {
+                throw new NoSuchBufferException(String.format(
+                        "the handler '%s' has no inbound byte buffer; it does not implement %s.",
+                        name, ChannelInboundHandler.class.getSimpleName()));
+            }
         }
         return inByteBuf;
     }
@@ -375,7 +385,17 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
     @SuppressWarnings("unchecked")
     public <T> MessageBuf<T> inboundMessageBuffer() {
         if (inMsgBuf == null) {
-            throw new NoSuchBufferException();
+            if (handler instanceof ChannelInboundHandler) {
+                throw new NoSuchBufferException(String.format(
+                        "the handler '%s' has no inbound message buffer; it implements %s, but " +
+                        "its newInboundBuffer() method created a %s.",
+                        name, ChannelInboundHandler.class.getSimpleName(),
+                        ByteBuf.class.getSimpleName()));
+            } else {
+                throw new NoSuchBufferException(String.format(
+                        "the handler '%s' has no inbound message buffer; it does not implement %s.",
+                        name, ChannelInboundHandler.class.getSimpleName()));
+            }
         }
         return (MessageBuf<T>) inMsgBuf;
     }
@@ -393,7 +413,17 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
     @Override
     public ByteBuf outboundByteBuffer() {
         if (outByteBuf == null) {
-            throw new NoSuchBufferException();
+            if (handler instanceof ChannelOutboundHandler) {
+                throw new NoSuchBufferException(String.format(
+                        "the handler '%s' has no outbound byte buffer; it implements %s, but " +
+                        "its newOutboundBuffer() method created a %s.",
+                        name, ChannelOutboundHandler.class.getSimpleName(),
+                        MessageBuf.class.getSimpleName()));
+            } else {
+                throw new NoSuchBufferException(String.format(
+                        "the handler '%s' has no outbound byte buffer; it does not implement %s.",
+                        name, ChannelOutboundHandler.class.getSimpleName()));
+            }
         }
         return outByteBuf;
     }
@@ -402,7 +432,17 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
     @SuppressWarnings("unchecked")
     public <T> MessageBuf<T> outboundMessageBuffer() {
         if (outMsgBuf == null) {
-            throw new NoSuchBufferException();
+            if (handler instanceof ChannelOutboundHandler) {
+                throw new NoSuchBufferException(String.format(
+                        "the handler '%s' has no outbound message buffer; it implements %s, but " +
+                        "its newOutboundBuffer() method created a %s.",
+                        name, ChannelOutboundHandler.class.getSimpleName(),
+                        ByteBuf.class.getSimpleName()));
+            } else {
+                throw new NoSuchBufferException(String.format(
+                        "the handler '%s' has no outbound message buffer; it does not implement %s.",
+                        name, ChannelOutboundHandler.class.getSimpleName()));
+            }
         }
         return (MessageBuf<T>) outMsgBuf;
     }
@@ -451,7 +491,17 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         final Thread currentThread = Thread.currentThread();
         for (;;) {
             if (ctx == null) {
-                throw new NoSuchBufferException();
+                if (prev != null) {
+                    throw new NoSuchBufferException(String.format(
+                            "the handler '%s' could not find a %s whose inbound buffer is %s.",
+                            name, ChannelInboundHandler.class.getSimpleName(),
+                            ByteBuf.class.getSimpleName()));
+                } else {
+                    throw new NoSuchBufferException(String.format(
+                            "the pipeline does not contain a %s whose inbound buffer is %s.",
+                            ChannelInboundHandler.class.getSimpleName(),
+                            ByteBuf.class.getSimpleName()));
+                }
             }
             if (ctx.inByteBuf != null) {
                 if (ctx.executor().inEventLoop(currentThread)) {
@@ -477,7 +527,17 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
         final Thread currentThread = Thread.currentThread();
         for (;;) {
             if (ctx == null) {
-                throw new NoSuchBufferException();
+                if (prev != null) {
+                    throw new NoSuchBufferException(String.format(
+                            "the handler '%s' could not find a %s whose inbound buffer is %s.",
+                            name, ChannelInboundHandler.class.getSimpleName(),
+                            MessageBuf.class.getSimpleName()));
+                } else {
+                    throw new NoSuchBufferException(String.format(
+                            "the pipeline does not contain a %s whose inbound buffer is %s.",
+                            ChannelInboundHandler.class.getSimpleName(),
+                            MessageBuf.class.getSimpleName()));
+                }
             }
 
             if (ctx.inMsgBuf != null) {

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

@@ -18,7 +18,6 @@ package io.netty.channel;
 import static io.netty.channel.DefaultChannelHandlerContext.*;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ChannelBuf;
-import io.netty.buffer.ChannelBufType;
 import io.netty.buffer.MessageBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.channel.DefaultChannelHandlerContext.ByteBridge;
@@ -898,19 +897,11 @@ public class DefaultChannelPipeline implements ChannelPipeline {
 
     @Override
     public MessageBuf<Object> inboundMessageBuffer() {
-        if (channel.metadata().bufferType() != ChannelBufType.MESSAGE) {
-            throw new NoSuchBufferException(
-                    "The first inbound buffer of this channel must be a message buffer.");
-        }
         return head.nextInboundMessageBuffer();
     }
 
     @Override
     public ByteBuf inboundByteBuffer() {
-        if (channel.metadata().bufferType() != ChannelBufType.BYTE) {
-            throw new NoSuchBufferException(
-                    "The first inbound buffer of this channel must be a byte buffer.");
-        }
         return head.nextInboundByteBuffer();
     }
 
@@ -951,10 +942,21 @@ public class DefaultChannelPipeline implements ChannelPipeline {
     }
 
     ByteBuf nextOutboundByteBuffer(DefaultChannelHandlerContext ctx) {
+        final DefaultChannelHandlerContext initialCtx = ctx;
         final Thread currentThread = Thread.currentThread();
         for (;;) {
             if (ctx == null) {
-                throw new NoSuchBufferException();
+                if (initialCtx.next != null) {
+                    throw new NoSuchBufferException(String.format(
+                            "the handler '%s' could not find a %s whose outbound buffer is %s.",
+                            initialCtx.next.name(), ChannelOutboundHandler.class.getSimpleName(),
+                            ByteBuf.class.getSimpleName()));
+                } else {
+                    throw new NoSuchBufferException(String.format(
+                            "the pipeline does not contain a %s whose outbound buffer is %s.",
+                            ChannelOutboundHandler.class.getSimpleName(),
+                            ByteBuf.class.getSimpleName()));
+                }
             }
 
             if (ctx.outByteBuf != null) {
@@ -976,10 +978,21 @@ public class DefaultChannelPipeline implements ChannelPipeline {
     }
 
     MessageBuf<Object> nextOutboundMessageBuffer(DefaultChannelHandlerContext ctx) {
+        final DefaultChannelHandlerContext initialCtx = ctx;
         final Thread currentThread = Thread.currentThread();
         for (;;) {
             if (ctx == null) {
-                throw new NoSuchBufferException();
+                if (initialCtx.next != null) {
+                    throw new NoSuchBufferException(String.format(
+                            "the handler '%s' could not find a %s whose outbound buffer is %s.",
+                            initialCtx.next.name(), ChannelOutboundHandler.class.getSimpleName(),
+                            MessageBuf.class.getSimpleName()));
+                } else {
+                    throw new NoSuchBufferException(String.format(
+                            "the pipeline does not contain a %s whose outbound buffer is %s.",
+                            ChannelOutboundHandler.class.getSimpleName(),
+                            MessageBuf.class.getSimpleName()));
+                }
             }
 
             if (ctx.outMsgBuf != null) {
@@ -1288,11 +1301,25 @@ public class DefaultChannelPipeline implements ChannelPipeline {
         }
         validateFuture(future);
 
+        final DefaultChannelHandlerContext initialCtx = ctx;
         EventExecutor executor;
         boolean msgBuf = false;
         for (;;) {
             if (ctx == null) {
-                throw new NoSuchBufferException();
+                if (initialCtx.next != null) {
+                    throw new NoSuchBufferException(String.format(
+                            "the handler '%s' could not find a %s which accepts a %s, and " +
+                            "the transport does not accept it as-is.",
+                            initialCtx.next.name(),
+                            ChannelOutboundHandler.class.getSimpleName(),
+                            message.getClass().getSimpleName()));
+                } else {
+                    throw new NoSuchBufferException(String.format(
+                            "the pipeline does not contain a %s which accepts a %s, and " +
+                            "the transport does not accept it as-is.",
+                            ChannelOutboundHandler.class.getSimpleName(),
+                            message.getClass().getSimpleName()));
+                }
             }
 
             if (ctx.hasOutboundMessageBuffer()) {

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

@@ -22,14 +22,9 @@ package io.netty.channel;
  */
 public class NoSuchBufferException extends ChannelPipelineException {
 
-    private static final String DEFAULT_MESSAGE =
-            "Could not find a suitable destination buffer.  Double-check if the pipeline is " +
-            "configured correctly and its handlers works as expected.";
-
     private static final long serialVersionUID = -131650785896627090L;
 
     public NoSuchBufferException() {
-        this(DEFAULT_MESSAGE);
     }
 
     public NoSuchBufferException(String message, Throwable cause) {