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:
We can just use Objects.requireNonNull(...) as a replacement for ObjectUtil.checkNotNull(....)
Modifications:
- Use Objects.requireNonNull(...)
Result:
Less code to maintain.
Motivation:
We can use the diamond operator these days.
Modification:
Use diamond operator whenever possible.
Result:
More modern code and less boiler-plate.
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.
Since 3.1.1 mqtt protocol version SUBACK message can now indicate the failure in payload.
Modification:
Do not erase failure payload in for SUBACK message.
Result:
Fixes#7665
Automatic-Module-Name entry provides a stable JDK9 module name, when Netty is used in a modular JDK9 applications. More info: http://blog.joda.org/2017/05/java-se-9-jpms-automatic-modules.html
When Netty migrates to JDK9 in the future, the entry can be replaced by actual module-info descriptor.
Modification:
The POM-s are configured to put the correct module names to the manifest.
Result:
Fixes#7218.
Motivation:
The MQTT decoder should raise an exception trying to build a CONNECT packet where password field is set but not the username one (as by MQTT 3.1/3.1.1 spec).
Modification:
Throw exception if password field is set but not the username
Result:
Fixes [#7205].
Motivation:
MQTT unknown message type isn't handled as decoding error
Modification:
Catching exception during the MQTT decoding of the fixed header
Adding a unit test for unknown MQTT message type
Result:
Fixes#6984.
