MQTT Event Receiver

MQTT event receiver is an internal event receiver that comes with WSO2 products. You can configure it with XML, JSON, and text input mapping types.

Prerequisites

Follow the steps below before starting the MQTT event receiver configurations.

Download MQTT client library (mqtt-client-0.4.0.jar).
Add the JAR file to the <PRODUCT_HOME>/repository/components/lib/ directory.
Start the MQTT-supported server.

Creating a MQTT event receiver

For instructions on creating a MQTT event receiver, see Configuring Event Receivers.

Configuring adapter properties

Specify the Adapter Properties , when creating a MQTT event receiver using the management console as shown below.

After entering the above adapter properties, select the Event Stream to which you want to map the incoming events, and the Message Format that you want to apply on the receiving events. Also, click Advanced to define custom input mappings based on the Message Format you selected. For more information on custom input mapping types, see Input Mapping Types.

You can also d efine the respective adapter properties of the event receiver based on the transport type within the <from> element of the event receiver configuration in the <PRODUCT_HOME>/repository/deployment/server/eventreceivers/ directory as follows.

 <eventReceiver name="MQTTInputEventAdapter" statistics="disable" trace="disable" xmlns="http://wso2.org/carbon/eventreceiver">
    <from eventAdapterType="mqtt">
        <property name="topic">sensordata</property>
        <property name="clientId">CEP-CONSUMER</property>
        <property name="url">tcp://localhost:1883</property>
        <property name="username">mqtt-user</property>
        <property name="password">mqtt-password</property>
        <property name="cleanSession">true</property>
    </from>
   ......................
</eventReceiver>

The above adapter properties are described below.

Adapter Property	Description	Configuration file property	Example
Topic	A valid name for the MQTT broker topic which is used to receive messages on the MQTT input event adapter.	topic	MQTTInputEventAdapter
Broker Url	MQTT broker URL. You can use the same URL f or WSO2 MB (when offset is zero).	url	tcp://localhost:1883
Username	A valid username for the broker connection .	`username`	mqtt-user
Password	A valid password for the broker connection .	password	mqtt-password
Clean Session	Persist topic subscriptions and acknowledge positions across client sessions.	cleanSession	true/false
Client Id	Unique client ID used by the server to identify a client when it reconnects. Used for durable subscriptions or reliable delivery of messages.	clientId	clientid

Related samples

For more information on MQTT event receiver type, see the following sample.

Sample 0016 - Receiving JSON Events via MQTT Transport