Issue #540

 - Throwing exception if duplicate invalid properties are decoded.
 - Cleanup of JavaDoc
 - Throw exception if incoming topic alias is 0.

Signed-off-by: James Sutton <james.sutton@uk.ibm.com>

Author: jpwsutton

org.eclipse.paho.mqttv5.client/src/main/java/org/eclipse/paho/mqttv5/client/internal/ClientComms.java

@@ -101,6 +101,8 @@ public class ClientComms {
 	 * @param executorService
 	 *            the {@link ExecutorService}
 	 * @param mqttSession
+	 *            the {@link MqttSessionState}
+	 * @param mqttConnection
 	 *            the {@link MqttConnectionState}
 	 * @throws MqttException
 	 *             if an exception occurs whilst communicating with the server

org.eclipse.paho.mqttv5.client/src/main/java/org/eclipse/paho/mqttv5/client/internal/ClientState.java

@@ -1188,7 +1188,7 @@ protected void notifyReceivedMsg(MqttWireMessage message) throws MqttException {
 				MqttPublish send = (MqttPublish) message;
 
 				// Do we have an incoming topic Alias?
-				if (send.getProperties().getTopicAlias() != null && send.getProperties().getTopicAlias() != 0) {
+				if (send.getProperties().getTopicAlias() != null) {
 					int incomingTopicAlias = send.getProperties().getTopicAlias();
 
 					// Are incoming Topic Aliases enabled / is it a valid Alias?

org.eclipse.paho.mqttv5.client/src/main/java/org/eclipse/paho/mqttv5/client/internal/ConnectActionListener.java

@@ -83,6 +83,8 @@ public class ConnectActionListener implements MqttActionListener {
 	 * @param userCallback
 	 *            the {@link MqttActionListener} as the callback for the user
 	 * @param mqttSession
+	 *            the {@link MqttSessionState}
+	 * @param mqttConnection
 	 *            the {@link MqttConnectionState}
 	 * @param reconnect
 	 *            If true, this is a reconnect attempt

org.eclipse.paho.mqttv5.common/src/main/java/org/eclipse/paho/mqttv5/common/MqttException.java

@@ -22,11 +22,17 @@ public class MqttException extends Exception {
 																	// the MQTTv5 specification
 	public static final int REASON_CODE_UNSUPPORTED_PROTOCOL_VERSION = 50003; // The CONNECT packet did not contain the
 																				// correct protocol name or version
+	
 
 	/**
 	 * The Server sent a publish message with an invalid topic alias.
 	 */
 	public static final int REASON_CODE_INVALID_TOPIC_ALAS = 50004;
+	
+	/**
+	 * The client attempted to decode a property that had already been decoded, and can only be included once.
+	 */
+	public static final int REASON_CODE_DUPLICATE_PROPERTY = 50005;
 
 	private int reasonCode;
 	private Throwable cause;

org.eclipse.paho.mqttv5.common/src/main/java/org/eclipse/paho/mqttv5/common/packet/MqttProperties.java

@@ -412,11 +412,22 @@ public void decodeProperties(DataInputStream dis) throws IOException, MqttExcept
 			byte[] identifierValueByteArray = new byte[length];
 			dis.read(identifierValueByteArray, 0, length);
 			ByteArrayInputStream bais = new ByteArrayInputStream(identifierValueByteArray);
+			ArrayList<Byte> decodedProperties = new ArrayList<Byte>();
 			DataInputStream inputStream = new DataInputStream(bais);
 			while (inputStream.available() > 0) {
 				// Get the first Byte
 				byte identifier = inputStream.readByte();
 				if (validProperties.contains(identifier)) {
+					
+					// Verify that certain properties are not included more than once
+					if(!decodedProperties.contains(identifier)) {
+						decodedProperties.add(identifier);
+					} else if(identifier!= SUBSCRIPTION_IDENTIFIER && identifier != USER_DEFINED_PAIR_IDENTIFIER) {
+						// This property can only be included once
+						throw new MqttException(MqttException.REASON_CODE_DUPLICATE_PROPERTY);
+					}
+					
+					
 
 					if (identifier == PAYLOAD_FORMAT_INDICATOR_IDENTIFIER) {
 						payloadFormat = (boolean) inputStream.readBoolean();