Overall clean-up on codec-mqtt

- Use simple string concatenation instead of String.format()
- Rewrite exception messages so that it follows our style
- Merge MqttCommonUtil and MqttValidationUtil into MqttCodecUtil
- Hide MqttCodecUtil from users
- Rename MqttConnectReturnCode.value to byteValue
- Rename MqttMessageFactory.create*() to new*()
- Rename QoS to MqttQoS
- Make MqttSubAckPayload.grantedQoSLevels immutable and add more useful
  constructor

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttCodecUtil.java

@@ -16,9 +16,45 @@
 
 package io.netty.handler.codec.mqtt;
 
-public final class MqttCommonUtil {
+import io.netty.handler.codec.DecoderException;
 
-    public static MqttFixedHeader resetUnusedFields(MqttFixedHeader mqttFixedHeader) {
+final class MqttCodecUtil {
+
+    private static final char[] TOPIC_WILDCARDS = {'#', '+'};
+    private static final int MAX_CLIENT_ID_LENGTH = 23;
+
+    static boolean isValidPublishTopicName(String topicName) {
+        // publish topic name must not contain any wildcard
+        for (char c : TOPIC_WILDCARDS) {
+            if (topicName.indexOf(c) >= 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    static boolean isValidMessageId(int messageId) {
+        return messageId != 0;
+    }
+
+    static boolean isValidClientId(String clientId) {
+        return clientId != null && clientId.length() <= MAX_CLIENT_ID_LENGTH;
+    }
+
+    static MqttFixedHeader validateFixedHeader(MqttFixedHeader mqttFixedHeader) {
+        switch (mqttFixedHeader.messageType()) {
+            case PUBREL:
+            case SUBSCRIBE:
+            case UNSUBSCRIBE:
+                if (mqttFixedHeader.qosLevel() != MqttQoS.AT_LEAST_ONCE) {
+                    throw new DecoderException(mqttFixedHeader.messageType().name() + " message must have QoS 1");
+                }
+            default:
+                return mqttFixedHeader;
+        }
+    }
+
+    static MqttFixedHeader resetUnusedFields(MqttFixedHeader mqttFixedHeader) {
         switch (mqttFixedHeader.messageType()) {
             case CONNECT:
             case CONNACK:
@@ -31,12 +67,12 @@ public final class MqttCommonUtil {
             case PINGRESP:
             case DISCONNECT:
                 if (mqttFixedHeader.isDup() ||
-                    mqttFixedHeader.qosLevel() != QoS.AT_MOST_ONCE ||
+                        mqttFixedHeader.qosLevel() != MqttQoS.AT_MOST_ONCE ||
-                    mqttFixedHeader.isRetain()) {
+                        mqttFixedHeader.isRetain()) {
                     return new MqttFixedHeader(
                             mqttFixedHeader.messageType(),
                             false,
-                            QoS.AT_MOST_ONCE,
+                            MqttQoS.AT_MOST_ONCE,
                             false,
                             mqttFixedHeader.remainingLength());
                 }
@@ -58,5 +94,5 @@ public final class MqttCommonUtil {
         }
     }
 
-    private MqttCommonUtil() { }
+    private MqttCodecUtil() { }
 }

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttConnAckMessage.java

@@ -29,5 +29,4 @@ public final class MqttConnAckMessage extends MqttMessage {
     public MqttConnAckVariableHeader variableHeader() {
         return (MqttConnAckVariableHeader) super.variableHeader();
     }
-
 }

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttConnAckVariableHeader.java

@@ -19,7 +19,7 @@ package io.netty.handler.codec.mqtt;
 import io.netty.util.internal.StringUtil;
 
 /**
- * Variable header of {@link MqttConnectMessage }
+ * Variable header of {@link MqttConnectMessage}
  */
 public class MqttConnAckVariableHeader {
 

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttConnectReturnCode.java

@@ -35,26 +35,26 @@ public enum MqttConnectReturnCode {
 
     static {
         final Map<Byte, MqttConnectReturnCode> valueMap = new HashMap<Byte, MqttConnectReturnCode>();
-        for (MqttConnectReturnCode code : values()) {
+        for (MqttConnectReturnCode code: values()) {
-            valueMap.put(code.value, code);
+            valueMap.put(code.byteValue, code);
         }
         valueToCodeMap = Collections.unmodifiableMap(valueMap);
     }
 
-    private final byte value;
+    private final byte byteValue;
 
-    MqttConnectReturnCode(byte value) {
+    MqttConnectReturnCode(byte byteValue) {
-        this.value = value;
+        this.byteValue = byteValue;
     }
 
-    public byte value() {
+    public byte byteValue() {
-        return value;
+        return byteValue;
     }
 
     public static MqttConnectReturnCode valueOf(byte b) {
         if (valueToCodeMap.containsKey(b)) {
             return valueToCodeMap.get(b);
         }
-        throw new IllegalArgumentException("connect retirn code " + b + " unsupported");
+        throw new IllegalArgumentException("unknown connect return code: " + (b & 0xFF));
     }
 }

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttDecoder.java

@@ -26,9 +26,7 @@ import io.netty.util.CharsetUtil;
 import java.util.ArrayList;
 import java.util.List;
 
-import static io.netty.handler.codec.mqtt.MqttValidationUtil.*;
+import static io.netty.handler.codec.mqtt.MqttCodecUtil.*;
-import static io.netty.handler.codec.mqtt.MqttCommonUtil.*;
-
 import static io.netty.handler.codec.mqtt.MqttVersion.*;
 
 /**
@@ -79,10 +77,7 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
 
             case READ_VARIABLE_HEADER:  try {
                 if (bytesRemainingInVariablePart > maxBytesInMessage) {
-                    throw new DecoderException(
+                    throw new DecoderException("too large message: " + bytesRemainingInVariablePart + " bytes");
-                            String.format(
-                                    "Client tried to send very large message: %d bytes",
-                                    bytesRemainingInVariablePart));
                 }
                 final Result<?> decodedVariableHeader = decodeVariableHeader(buffer, mqttFixedHeader);
                 variableHeader = decodedVariableHeader.value;
@@ -105,15 +100,11 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
                 bytesRemainingInVariablePart -= decodedPayload.numberOfBytesConsumed;
                 if (bytesRemainingInVariablePart != 0) {
                     throw new DecoderException(
-                            String.format(
+                            "non-zero remaining payload bytes: " +
-                                    "Non-zero bytes remaining (%d) should never happen. "
+                                    bytesRemainingInVariablePart + " (" + mqttFixedHeader.messageType() + ')');
-                                            + "Message type: %s. Channel: %s",
-                                    bytesRemainingInVariablePart,
-                                    mqttFixedHeader.messageType(),
-                                    ctx.channel()));
                 }
                 checkpoint(DecoderState.READ_FIXED_HEADER);
-                MqttMessage message = MqttMessageFactory.create(mqttFixedHeader, variableHeader, payload);
+                MqttMessage message = MqttMessageFactory.newMessage(mqttFixedHeader, variableHeader, payload);
                 mqttFixedHeader = null;
                 variableHeader = null;
                 payload = null;
@@ -130,13 +121,14 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
                 break;
 
             default:
-                throw new Error("Shouldn't reach here");
+                // Shouldn't reach here.
+                throw new Error();
         }
     }
 
     private MqttMessage invalidMessage(Throwable cause) {
       checkpoint(DecoderState.BAD_MESSAGE);
-      return MqttMessageFactory.createInvalidMessage(cause);
+      return MqttMessageFactory.newInvalidMessage(cause);
     }
 
     /**
@@ -166,15 +158,10 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
 
         // MQTT protocol limits Remaining Length to 4 bytes
         if (loops == 4 && (digit & 128) != 0) {
-            throw new DecoderException(
+            throw new DecoderException("remaining length exceeds 4 digits (" + messageType + ')');
-                    String.format(
-                            "Failed to read fixed header of MQTT message. " +
-                                    "It has more than 4 digits for Remaining Length. " +
-                                    "MqttMessageType: %s.",
-                            messageType));
         }
         MqttFixedHeader decodedFixedHeader =
-                new MqttFixedHeader(messageType, dupFlag, QoS.valueOf(qosLevel), retain, remainingLength);
+                new MqttFixedHeader(messageType, dupFlag, MqttQoS.valueOf(qosLevel), retain, remainingLength);
         return validateFixedHeader(resetUnusedFields(decodedFixedHeader));
     }
 
@@ -217,7 +204,7 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
     private static Result<MqttConnectVariableHeader> decodeConnectionVariableHeader(ByteBuf buffer) {
         final Result<String> protoString = decodeString(buffer);
         if (!PROTOCOL_NAME.equals(protoString.value)) {
-            throw new DecoderException(PROTOCOL_NAME + " signature is missing. Closing channel.");
+            throw new DecoderException("missing " + PROTOCOL_NAME + " signature");
         }
 
         int numberOfBytesConsumed = protoString.numberOfBytesConsumed;
@@ -270,7 +257,7 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
             MqttFixedHeader mqttFixedHeader) {
         final Result<String> decodedTopic = decodeString(buffer);
         if (!isValidPublishTopicName(decodedTopic.value)) {
-            throw new DecoderException(String.format("Publish topic name %s contains wildcards.", decodedTopic.value));
+            throw new DecoderException("invalid publish topic name: " + decodedTopic.value + " (contains wildcards)");
         }
         int numberOfBytesConsumed = decodedTopic.numberOfBytesConsumed;
 
@@ -288,7 +275,7 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
     private static Result<Integer> decodeMessageId(ByteBuf buffer) {
         final Result<Integer> messageId = decodeMsbLsb(buffer);
         if (!isValidMessageId(messageId.value)) {
-            throw new DecoderException(String.format("Invalid messageId %d", messageId.value));
+            throw new DecoderException("invalid messageId: " + messageId.value);
         }
         return messageId;
     }
@@ -335,9 +322,7 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
         final Result<String> decodedClientId = decodeString(buffer);
         final String decodedClientIdValue = decodedClientId.value;
         if (!isValidClientId(decodedClientIdValue)) {
-            throw new DecoderException(
+            throw new DecoderException("invalid clientIdentifier: " + decodedClientIdValue);
-                    String.format("Invalid clientIdentifier %s ",
-                                  decodedClientIdValue != null ? decodedClientIdValue : "null"));
         }
         int numberOfBytesConsumed = decodedClientId.numberOfBytesConsumed;
 
@@ -380,7 +365,7 @@ public class MqttDecoder extends ReplayingDecoder<DecoderState> {
             numberOfBytesConsumed += decodedTopicName.numberOfBytesConsumed;
             int qos = buffer.readUnsignedByte() & 0x03;
             numberOfBytesConsumed++;
-            subscribeTopics.add(new MqttTopicSubscription(decodedTopicName.value, QoS.valueOf(qos)));
+            subscribeTopics.add(new MqttTopicSubscription(decodedTopicName.value, MqttQoS.valueOf(qos)));
         }
         return new Result<MqttSubscribePayload>(new MqttSubscribePayload(subscribeTopics), numberOfBytesConsumed);
     }

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttEncoder.java

@@ -102,8 +102,7 @@ public class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
         String clientIdentifier = payload.clientIdentifier();
         if (!isValidClientIdentifier(clientIdentifier)) {
             throw new IllegalArgumentException(
-                    String.format("Invalid clientIdentifier %s. Must be less than 23 chars long",
+                    "invalid clientIdentifier: " + clientIdentifier + " (expected: less than 23 chars long)");
-                            clientIdentifier != null ? clientIdentifier : "null"));
         }
         byte[] clientIdentifierBytes = encodeStringUtf8(clientIdentifier);
         payloadBufferSize += 2 + clientIdentifierBytes.length;
@@ -191,7 +190,7 @@ public class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
         buf.writeByte(getFixedHeaderByte1(message.fixedHeader()));
         buf.writeByte(2);
         buf.writeByte(0);
-        buf.writeByte(message.variableHeader().connectReturnCode().value());
+        buf.writeByte(message.variableHeader().connectReturnCode().byteValue());
 
         return buf;
     }
@@ -391,5 +390,4 @@ public class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
         int length = clientIdentifier.length();
         return length >= 1 && length <= 23;
     }
-
 }

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttFixedHeader.java

@@ -26,14 +26,14 @@ public class MqttFixedHeader {
 
     private final MqttMessageType messageType;
     private final boolean isDup;
-    private final QoS qosLevel;
+    private final MqttQoS qosLevel;
     private final boolean isRetain;
     private final int remainingLength;
 
     public MqttFixedHeader(
             MqttMessageType messageType,
             boolean isDup,
-            QoS qosLevel,
+            MqttQoS qosLevel,
             boolean isRetain,
             int remainingLength) {
         this.messageType = messageType;
@@ -51,7 +51,7 @@ public class MqttFixedHeader {
         return isDup;
     }
 
-    public QoS qosLevel() {
+    public MqttQoS qosLevel() {
         return qosLevel;
     }
 
@@ -74,5 +74,4 @@ public class MqttFixedHeader {
         builder.append(']');
         return builder.toString();
     }
-
 }

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttMessageFactory.java

@@ -24,7 +24,7 @@ import io.netty.handler.codec.DecoderResult;
  */
 public final class MqttMessageFactory {
 
-    public static MqttMessage create(MqttFixedHeader mqttFixedHeader, Object variableHeader, Object payload) {
+    public static MqttMessage newMessage(MqttFixedHeader mqttFixedHeader, Object variableHeader, Object payload) {
         switch (mqttFixedHeader.messageType()) {
             case CONNECT :
                 return new MqttConnectMessage(
@@ -77,11 +77,11 @@ public final class MqttMessageFactory {
                 return new MqttMessage(mqttFixedHeader);
 
             default:
-                throw new IllegalArgumentException("Unknown message type: " + mqttFixedHeader.messageType());
+                throw new IllegalArgumentException("unknown message type: " + mqttFixedHeader.messageType());
         }
     }
 
-    public static MqttMessage createInvalidMessage(Throwable cause) {
+    public static MqttMessage newInvalidMessage(Throwable cause) {
         return new MqttMessage(null, null, null, DecoderResult.failure(cause));
     }
 

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttMessageIdVariableHeader.java

@@ -28,9 +28,7 @@ public final class MqttMessageIdVariableHeader {
 
     public static MqttMessageIdVariableHeader from(int messageId) {
       if (messageId < 1 || messageId > 0xffff) {
-        throw new IllegalArgumentException(
+        throw new IllegalArgumentException("messageId: " + messageId + " (expected: 1 ~ 65535)");
-            String.format("Message id must be in the range of 1 - 0xffff but %d given ",
-                          messageId));
       }
       return new MqttMessageIdVariableHeader(messageId);
     }

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttMessageType.java

@@ -51,7 +51,7 @@ public enum MqttMessageType {
                 return t;
             }
         }
-        throw new IllegalArgumentException("message type " + type + " unsupported");
+        throw new IllegalArgumentException("unknown message type: " + type);
     }
 }
 

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttQoS.java

@@ -15,13 +15,14 @@
 
 package io.netty.handler.codec.mqtt;
 
-public enum QoS {
+public enum MqttQoS {
     AT_MOST_ONCE(0),
     AT_LEAST_ONCE(1),
     EXACTLY_ONCE(2);
 
     private final int value;
-    QoS(int value) {
+
+    MqttQoS(int value) {
         this.value = value;
     }
 
@@ -29,12 +30,12 @@ public enum QoS {
         return value;
     }
 
-    public static QoS valueOf(int value) {
+    public static MqttQoS valueOf(int value) {
-        for (QoS q : values()) {
+        for (MqttQoS q: values()) {
             if (q.value == value) {
                 return q;
             }
         }
-        throw new IllegalArgumentException(String.format("Invalid QoS: %d", value));
+        throw new IllegalArgumentException("invalid QoS: " + value);
     }
 }

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttSubAckPayload.java

@@ -18,6 +18,8 @@ package io.netty.handler.codec.mqtt;
 
 import io.netty.util.internal.StringUtil;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -27,8 +29,30 @@ public class MqttSubAckPayload {
 
     private final List<Integer> grantedQoSLevels;
 
-    public MqttSubAckPayload(List<Integer> grantedQoSLevels) {
+    public MqttSubAckPayload(int... grantedQoSLevels) {
-        this.grantedQoSLevels = grantedQoSLevels;
+        if (grantedQoSLevels == null) {
+            throw new NullPointerException("grantedQoSLevels");
+        }
+
+        List<Integer> list = new ArrayList<Integer>(grantedQoSLevels.length);
+        for (int v: grantedQoSLevels) {
+            list.add(v);
+        }
+        this.grantedQoSLevels = Collections.unmodifiableList(list);
+    }
+
+    public MqttSubAckPayload(Iterable<Integer> grantedQoSLevels) {
+        if (grantedQoSLevels == null) {
+            throw new NullPointerException("grantedQoSLevels");
+        }
+        List<Integer> list = new ArrayList<Integer>();
+        for (Integer v: grantedQoSLevels) {
+            if (v == null) {
+                break;
+            }
+            list.add(v);
+        }
+        this.grantedQoSLevels = Collections.unmodifiableList(list);
     }
 
     public List<Integer> grantedQoSLevels() {

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttTopicSubscription.java

@@ -25,9 +25,9 @@ import io.netty.util.internal.StringUtil;
 public class MqttTopicSubscription {
 
     private final String topicFilter;
-    private final QoS qualityOfService;
+    private final MqttQoS qualityOfService;
 
-    public MqttTopicSubscription(String topicFilter, QoS qualityOfService) {
+    public MqttTopicSubscription(String topicFilter, MqttQoS qualityOfService) {
         this.topicFilter = topicFilter;
         this.qualityOfService = qualityOfService;
     }
@@ -36,7 +36,7 @@ public class MqttTopicSubscription {
         return topicFilter;
     }
 
-    public QoS qualityOfService() {
+    public MqttQoS qualityOfService() {
         return qualityOfService;
     }
 

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttValidationUtil.java

@@ -1,59 +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.mqtt;
-
-import io.netty.handler.codec.DecoderException;
-
-public final class MqttValidationUtil {
-
-    private static final char[] TOPIC_WILDCARDS = {'#', '+'};
-    private static final int MAX_CLIENT_ID_LENGTH = 23;
-
-    public static boolean isValidPublishTopicName(String topicName) {
-        // publish topic name must not contain any wildcard
-        for (char c : TOPIC_WILDCARDS) {
-            if (topicName.indexOf(c) >= 0) {
-                return false;
-            }
-        }
-        return true;
-    }
-
-    public static boolean isValidMessageId(int messageId) {
-        return messageId != 0;
-    }
-
-    public static boolean isValidClientId(String clientId) {
-        return clientId != null && clientId.length() <= MAX_CLIENT_ID_LENGTH;
-    }
-
-    public static MqttFixedHeader validateFixedHeader(MqttFixedHeader mqttFixedHeader) {
-        switch (mqttFixedHeader.messageType()) {
-            case PUBREL:
-            case SUBSCRIBE:
-            case UNSUBSCRIBE:
-                if (mqttFixedHeader.qosLevel() != QoS.AT_LEAST_ONCE) {
-                    throw new DecoderException(String.format("%s message must have QoS 1",
-                                               mqttFixedHeader.messageType().name()));
-                }
-            default:
-                return mqttFixedHeader;
-        }
-    }
-
-    private MqttValidationUtil() { }
-}

codec-mqtt/src/test/java/io/netty/handler/codec/mqtt/MqttCodecTest.java

@@ -235,7 +235,7 @@ public class MqttCodecTest {
     // Message types to help testing
 
     private static MqttMessage createMessageWithFixedHeader(MqttMessageType messageType) {
-        return new MqttMessage(new MqttFixedHeader(messageType, false, QoS.AT_MOST_ONCE, false, 0));
+        return new MqttMessage(new MqttFixedHeader(messageType, false, MqttQoS.AT_MOST_ONCE, false, 0));
     }
 
     private static MqttMessage createMessageWithFixedHeaderAndMessageIdVariableHeader(MqttMessageType messageType) {
@@ -243,7 +243,7 @@ public class MqttCodecTest {
                 new MqttFixedHeader(
                         messageType,
                         false,
-                        messageType == MqttMessageType.PUBREL ? QoS.AT_LEAST_ONCE :  QoS.AT_MOST_ONCE,
+                        messageType == MqttMessageType.PUBREL ? MqttQoS.AT_LEAST_ONCE :  MqttQoS.AT_MOST_ONCE,
                         false,
                         0);
         MqttMessageIdVariableHeader mqttMessageIdVariableHeader = MqttMessageIdVariableHeader.from(12345);
@@ -252,7 +252,7 @@ public class MqttCodecTest {
 
     private static MqttConnectMessage createConnectMessage() {
         MqttFixedHeader mqttFixedHeader =
-                new MqttFixedHeader(MqttMessageType.CONNECT, false, QoS.AT_MOST_ONCE, false, 0);
+                new MqttFixedHeader(MqttMessageType.CONNECT, false, MqttQoS.AT_MOST_ONCE, false, 0);
         MqttConnectVariableHeader mqttConnectVariableHeader =
                 new MqttConnectVariableHeader(
                         PROTOCOL_NAME,
@@ -272,7 +272,7 @@ public class MqttCodecTest {
 
     private static MqttConnAckMessage createConnAckMessage() {
         MqttFixedHeader mqttFixedHeader =
-                new MqttFixedHeader(MqttMessageType.CONNACK, false, QoS.AT_MOST_ONCE, false, 0);
+                new MqttFixedHeader(MqttMessageType.CONNACK, false, MqttQoS.AT_MOST_ONCE, false, 0);
         MqttConnAckVariableHeader mqttConnAckVariableHeader =
                 new MqttConnAckVariableHeader(MqttConnectReturnCode.CONNECTION_ACCEPTED);
         return new MqttConnAckMessage(mqttFixedHeader, mqttConnAckVariableHeader);
@@ -280,7 +280,7 @@ public class MqttCodecTest {
 
     private static MqttPublishMessage createPublishMessage() {
         MqttFixedHeader mqttFixedHeader =
-                new MqttFixedHeader(MqttMessageType.PUBLISH, false, QoS.AT_LEAST_ONCE, true, 0);
+                new MqttFixedHeader(MqttMessageType.PUBLISH, false, MqttQoS.AT_LEAST_ONCE, true, 0);
         MqttPublishVariableHeader mqttPublishVariableHeader = new MqttPublishVariableHeader("/abc", 1234);
         ByteBuf payload =  ALLOCATOR.buffer();
         payload.writeBytes("whatever".getBytes(CharsetUtil.UTF_8));
@@ -289,13 +289,13 @@ public class MqttCodecTest {
 
     private static MqttSubscribeMessage createSubscribeMessage() {
         MqttFixedHeader mqttFixedHeader =
-                new MqttFixedHeader(MqttMessageType.SUBSCRIBE, false, QoS.AT_LEAST_ONCE, true, 0);
+                new MqttFixedHeader(MqttMessageType.SUBSCRIBE, false, MqttQoS.AT_LEAST_ONCE, true, 0);
         MqttMessageIdVariableHeader mqttMessageIdVariableHeader = MqttMessageIdVariableHeader.from(12345);
 
         List<MqttTopicSubscription> topicSubscriptions = new LinkedList<MqttTopicSubscription>();
-        topicSubscriptions.add(new MqttTopicSubscription("/abc", QoS.AT_LEAST_ONCE));
+        topicSubscriptions.add(new MqttTopicSubscription("/abc", MqttQoS.AT_LEAST_ONCE));
-        topicSubscriptions.add(new MqttTopicSubscription("/def", QoS.AT_LEAST_ONCE));
+        topicSubscriptions.add(new MqttTopicSubscription("/def", MqttQoS.AT_LEAST_ONCE));
-        topicSubscriptions.add(new MqttTopicSubscription("/xyz", QoS.EXACTLY_ONCE));
+        topicSubscriptions.add(new MqttTopicSubscription("/xyz", MqttQoS.EXACTLY_ONCE));
 
         MqttSubscribePayload mqttSubscribePayload = new MqttSubscribePayload(topicSubscriptions);
         return new MqttSubscribeMessage(mqttFixedHeader, mqttMessageIdVariableHeader, mqttSubscribePayload);
@@ -303,19 +303,15 @@ public class MqttCodecTest {
 
     private static MqttSubAckMessage createSubAckMessage() {
         MqttFixedHeader mqttFixedHeader =
-                new MqttFixedHeader(MqttMessageType.SUBACK, false, QoS.AT_MOST_ONCE, false, 0);
+                new MqttFixedHeader(MqttMessageType.SUBACK, false, MqttQoS.AT_MOST_ONCE, false, 0);
         MqttMessageIdVariableHeader mqttMessageIdVariableHeader = MqttMessageIdVariableHeader.from(12345);
-        List<Integer> grantedQosLevels = new LinkedList<Integer>();
+        MqttSubAckPayload mqttSubAckPayload = new MqttSubAckPayload(1, 2, 0);
-        grantedQosLevels.add(1);
-        grantedQosLevels.add(2);
-        grantedQosLevels.add(0);
-        MqttSubAckPayload mqttSubAckPayload = new MqttSubAckPayload(grantedQosLevels);
         return new MqttSubAckMessage(mqttFixedHeader, mqttMessageIdVariableHeader, mqttSubAckPayload);
     }
 
     private static MqttUnsubscribeMessage createUnsubscribeMessage() {
         MqttFixedHeader mqttFixedHeader =
-                new MqttFixedHeader(MqttMessageType.UNSUBSCRIBE, false, QoS.AT_LEAST_ONCE, true, 0);
+                new MqttFixedHeader(MqttMessageType.UNSUBSCRIBE, false, MqttQoS.AT_LEAST_ONCE, true, 0);
         MqttMessageIdVariableHeader mqttMessageIdVariableHeader = MqttMessageIdVariableHeader.from(12345);
 
         List<String> topics = new LinkedList<String>();