Paho

Paho Component

Available as of Camel 2.16

Paho component provides connector for the MQTT messaging protocol using the Paho library.

Adding the component to the project

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-paho</artifactId>
    <version>x.y.z</version>
    <!-- use the same version as your Camel core version -->
</dependency>

Keep in mind that Paho artifacts are not hosted in the Maven Central, so you need to add Eclipse Paho repository to your POM xml file:

<repositories>
  <repository>
    <id>eclipse-paho</id>
    <url>https://repo.eclipse.org/content/repositories/paho-releases</url>
    <snapshots>
      <enabled>false</enabled>
    </snapshots>
  </repository>
</repositories>

Default payload type

By default Camel Paho component operates on the binary payloads extracted out of or put into the MQTT message:

// Receive payload
byte[] payload = (byte[]) consumerTemplate.receiveBody("paho:topic");
 
// Send payload
byte[] payload = "message".getBytes();
producerTemplate.sendBody("paho:topic", payload);

But of course Camel can perform the automatic data type conversions for you:

// Receive payload
String payload = consumerTemplate.receiveBody("paho:topic", String.class);
 
// Send payload
String payload = "message";
producerTemplate.sendBody("paho:topic", payload);

URI format

paho:queueName[?options]

You can append query options to the URI in the following format: ?option=value&option=value&... .

URI Options

Option	Default	Description
`clientId`	`camel-<timestamp>`	MQTT client identifier.
`brokerUrl`	`tcp://localhost:1883`	The URL of the MQTT broker.
`persistence`	`memory`	Client persistence to be used - `memory` or `file`.
`qos`	2	Client quality of service level (`0`-`2`).
`connectOptions`	none	The reference to the `org.eclipse.paho.client.mqttv3.MqttConnectOptions` instance located in the Camel registry. Referenced `MqttConnectOptions` instance will be used by the endpoint to initialize the connection. For example `connectOptions=#myConnectOptions` notation can be used to reference Spring bean named `myConnectOptions.`

Headers

The following headers are recognized by the Paho component:

Header	Java constant	Endpoint type	Value type	Description
`PahoOriginalMessage`	`PahoConstants.HEADER_ORIGINAL_MESSAGE`	Consumer	`org.eclipse.paho.client.mqttv3.MqttMessage`	The original Paho message instance received by the client.

Examples

Read messages from the MQTT broker installed on the same host as the Camel router:

from("paho:some/queue").
  to("mock:test");

Read messages from the remote MQTT broker:

from("paho:some/queue?brokerUrl=tcp://iot.eclipse.org:1883").
  to("mock:test");

Send message to the MQTT broker:

from("direct:test").
  to("paho:some/target/queue");

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