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Publishing XML Events via MQTT¶

Purpose:¶

This application demonstrates how to configure WSO2 Streaming Integrator Tooling to send sweet production events via MQTT transport in XML format and view the output on the mqtt-consumer.

Prerequisites:¶

Save this sample. The following message appears on the console.
```
Siddhi App PublishMqttInXmlFormat successfully deployed.
```
Setting up MQTT Mosquitto broker in Ubuntu Linux.
1. Add the mosquitto repository using the following commands.
```
sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa
sudo apt-get update
```
2. Execute the following command to install the Mosquitto broker package. ```bash sudo apt-get install mosquitto ````
3. Install Mosquitto developer libraries to develop MQTT clients.
```
sudo apt-get install libmosquitto-dev
```
4. Execute the following command to install Mosquitto client packages.
```
sudo apt-get install mosquitto-clients
```
5. Ensure that the Mosquitto broker is running.
```
sudo service mosquitto status
```

Executing the Sample:¶

Open a terminal, navigate to the {WSO2SIHome}/samples/sample-clients/mqtt-consumer directory and run the ant command.
- If you use the default topic mqtt_topic and URL tcp://localhost:1883, in your program use the ant command without any arguments.
- However, if you use a different topic, run the ant command with appropriate argument. e.g. ant -Dtopic=mqttTest
Start the Siddhi application by clicking 'Run'.
If the Siddhi application starts successfully, the following messages appear on the console
```
PublishMqttInXmlFormat.siddhi - Started Successfully!
```

Testing the Sample:¶

Open the event simulator by clicking on the second icon or press Ctrl+Shift+I.
In the Single Simulation tab of the panel, select values as follows:
- Siddhi App Name: PublishMqttInXmlFormat
- Stream Name: SweetProductionStream
In the name field and amount fields, enter 'toffee' and '45.24' respectively. Then click Send to send the event.
Send some more events.

Viewing the Results:¶

See the output in the terminal of {WSO2SIHome}/samples/sample-clients/mqtt-consumer. You will get the output as follows (example for 3 events):

[java] [org.apache.axiom.om.util.StAXUtils] : XMLStreamReader is org.apache.axiom.util.stax.dialect.SJSXPStreamReaderWrapper
[java] [io.siddhi.core.stream.output.sink.LogSink] : PublishMqttInXmlFormatTest : logStream : Event{timestamp=1512462478777, data=[chocolate, 78.34], isExpired=false}
[java] [org.apache.axiom.om.util.StAXUtils] : XMLStreamReader is org.apache.axiom.util.stax.dialect.SJSXPStreamReaderWrapper
[java] [io.siddhi.core.stream.output.sink.LogSink] : PublishMqttInXmlFormatTest : logStream : Event{timestamp=1512462520264, data=[sweets, 34.57], isExpired=false}
[java] [org.apache.axiom.om.util.StAXUtils] : XMLStreamReader is org.apache.axiom.util.stax.dialect.SJSXPStreamReaderWrapper
[java] [io.siddhi.core.stream.output.sink.LogSink] : PublishMqttInXmlFormatTest : logStream : Event{timestamp=1512462534053, data=[coffee, 12.7], isExpired=false}

Notes:¶

If you need to edit this application while it is running, stop the application -> Save -> Start. If the message "LowProductionAlertStream' stream could not connect to 'localhost:1883", it could be due to port 1883, which is defined in the Siddhi application. This port is already being used by a different program. To resolve this issue, please do the following: * Stop this Siddhi application (click 'Run' on the menu bar -> 'Stop'). * Change the port 1883 to an unused port. To do this you need to add a new listener in mosquitto.conf (e.g., listener port 1884,listener port 1885). * Start the application and check whether the expected output appears on the console.

@App:name("PublishMqttInXmlFormat")
define stream SweetProductionStream (name string, amount double);

@sink(type='mqtt', url= 'tcp://localhost:1883',topic='mqtt_topic',
    @map(type='xml'))
define stream LowProductionAlertStream (name string, amount double);

from SweetProductionStream
select *
insert into LowProductionAlertStream;

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