Motivation:
Currently, the only way to create fixed-header only messages PINGREQ,
PINGRESP and DISCONNECT is to explicitly instantiate a `MqttFixedHeader` like:
```
MqttFixedHeader disconnectFixedHeader = new MqttFixedHeader(MqttMessageType.DISCONNECT,
false, MqttQoS.AT_MOST_ONCE, false, 0);
MqttMessage disconnectMessage = new MqttMessage(disconnectFixedHeader);
```
According to the MQTT spec
(http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718077),
the fixed-header flags for these messages are reserved and must be set to zero, otherwise
the receiver must close the connection. It's easy to mess this up when
you're creating the header explicitly, for e.g by setting the QoS bit to
`AT_LEAST_ONCE`.
As such, provide static constants for PINGREQ, PINGRESP and
DISCONNECT messages that will set the flags correctly for the developer.
Modification:
Add static constants to MqttMessage class to construct PINGREQ, PINGRESP and
DISCONNECT messages that will set the fixed-header flags correctly to 0.
Result:
Easier usage.
Motivation:
The toString() method should use Arrays.toString() to produce a meaningful String representation for arrays.
Modification:
Use Arrays.toString()
Result:
More useful toString() implementation
Motivation:
The toString() methods of MqttSubscribePayload and MqttUnsubscribePayload are causing exceptions when no topics are set.
Modification:
The toString() methods will not throw Excpetions anymore.
Result:
Fixes#9197
Motivation:
Most of the maven modules do not explicitly declare their
dependencies and rely on transitivity, which is not always correct.
Modifications:
For all maven modules, add all of their dependencies to pom.xml
Result:
All of the (essentially non-transitive) depepdencies of the modules are explicitly declared in pom.xml
Motivation:
When the MqttDecoder decodes a message larger than the 'maxBytesInMessage' a DecoderException is thrown and a MqttMessage with just the failure cause is returned. Even if I can't handle the message, I might want to send an ACK so that I won't have to worry about it again.
Modification:
The DecoderException is thrown after the variableHeader is decoded. The fixed and variable headers are then added to the MqttMessage along with the failure cause.
Result:
The invalid MqttMessage will have headers if available.
