org.eclipse.paho.client.mqttv3

Class MqttMessage

java.lang.Object

org.eclipse.paho.client.mqttv3.MqttMessage

public class MqttMessage
extends Object

An MQTT message holds the application payload and options specifying how the message is to be delivered The message includes a "payload" (the body of the message) represented as a byte[].

Constructor Summary

Constructors

Constructor and Description
MqttMessage() Constructs a message with an empty payload, and all other values set to defaults.
MqttMessage(byte[] payload) Constructs a message with the specified byte array as a payload, and all other values set to defaults.

Method Summary

Modifier and Type	Method and Description
byte[]	getPayload() Returns the payload as a byte array.
int	getQos() Returns the quality of service for this message.
boolean	isRetained() Returns whether or not this message should be/was retained by the server.
void	setPayload(byte[] payload) Sets the payload of this message to be the specified byte array.
void	setQos(int qos) Sets the quality of service for this message.
void	setRetained(boolean retained) Whether or not the publish message should be retained by the messaging engine.
String	toString() Returns a string representation of this message's payload.
static void	validateQos(int qos) Utility method to validate the supplied QoS value.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

MqttMessage

public MqttMessage()

Constructs a message with an empty payload, and all other values set to defaults. The defaults are:

• Message QoS set to 1
• Message will not be "retained" by the server

MqttMessage

public MqttMessage(byte[] payload)

Constructs a message with the specified byte array as a payload, and all other values set to defaults.

Parameters:

payload - The Bytearray of the payload. Important Note : The array is not cloned for memory efficiency reasons. Be careful with it.

Method Detail

getPayload

public byte[] getPayload()

Returns the payload as a byte array.

Returns:

the payload as a byte array. Important Note : The array is not cloned for memory efficiency reasons. Be careful with it.

getQos

public int getQos()

Returns the quality of service for this message.

Returns:

the quality of service to use, either 0, 1.

See Also:

setQos(int)

isRetained

public boolean isRetained()

Returns whether or not this message should be/was retained by the server. For messages received from the server, this method returns whether or not the message was from a current publisher, or was "retained" by the server as the last message published on the topic.

Returns:

true if the message should be, or was, retained by the server.

See Also:

setRetained(boolean)

setPayload

public void setPayload(byte[] payload)

Sets the payload of this message to be the specified byte array.

Parameters:

payload - the payload for this message. Important Note : The array is not cloned for memory efficiency reasons. Be careful with it.

setQos

public void setQos(int qos)

Sets the quality of service for this message.

• Quality of Service 0 - indicates that a message should be delivered at most once (zero or one times). The message will not be persisted to disk, and will not be acknowledged across the network. This QoS is the fastest, but should only be used for messages which are not valuable. Also known as "fire and forget".
• Quality of Service 1 - indicates that a message should be delivered at least once (one or more times). The message will be acknowledged across the network. This is the default QoS.

Parameters:

qos - the "quality of service" to use. Set to 0 or 1.

Throws:

IllegalArgumentException - if value of QoS is not 0 or 1.

IllegalStateException - if this message cannot be edited

setRetained

public void setRetained(boolean retained)

Whether or not the publish message should be retained by the messaging engine. Sending a message with retained set to true and with an empty byte array as the payload e.g. new byte[0] will clear the retained message from the server. The default value is false

Parameters:

retained - whether or not the messaging engine should retain the message.

toString

public String toString()

Returns a string representation of this message's payload. Makes an attempt to return the payload as a string. As the MQTT client has no control over the content of the payload it may fail.

Overrides:

toString in class Object

Returns:

a string representation of this message.

validateQos

public static void validateQos(int qos)

Utility method to validate the supplied QoS value.

Parameters:

qos - The QoS Level

Throws:

IllegalArgumentException - if value of QoS is not 0, 1 or 2.