Spring XD Source Module Template

Introduction

Spring XD ships with many source modules including HTTP/REST, TCP, and various messaging systems such as JMS and RabbitMQ. However, advanced users may encounter the need to create custom source modules. This template project provides a starting point to create custom source modules.

Project Components

Source modules in Spring XD are defined as Spring Integration output adapters. Therefore, the creation of a custom module requires the wiring of a Spring Integration adapter and placing it in the $XD_HOME/xd/modules/source directory.

Gradle Build

The first place to start is the build.gradle file that ships with this project. Other than setting dependencies, this build file contains a target called xdModule. This will create a build/modules/source/sample directory which contains the module artifacts. This directory should be moved/copied/sym-linked to the $XD_HOME/xd/modules/source directory when the module is ready for use.

What To Change

The following sections of the Gradle build file should be customized for your project:

On line 1, change description to match your module's description:

description = 'Spring XD Template Module' // TODO: Change this to match your module

On line 17, modify moduleName to match the name of your module:

moduleName = 'template' // TODO: change this to match the name of your module

On line 49, add any project dependencies, if any.

Java Source

The Java class ModuleTemplate extends from a convenient super class MessageProducerSupport which provides the ability to send messages as well as lifecycle hooks. Here are the key highlights:

• doStart and doStop methods
• dedicated thread for creating source output
• sendMessage is invoked when the module has output
• the optional use of Tuple

What To Change

Rename the class to match the name of your module.

On line 46, change "source-template" to match the desired name of your module's execution thread.

Rename the Runnable class on line 62 to match the desired name of your module's Runnable class.

Modify the run method starting at line 65 to perform your module's output routine. Note that sendMessage must be invoked in order for your module's output to be sent to the channel.

Module XML file

The module XML file consists of:

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns:beans="http://www.springframework.org/schema/beans"
			 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
			 xmlns="http://www.springframework.org/schema/integration"
			 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration.xsd">

	<channel id="output"/>

	<beans:bean class="hello.Sample">
		<beans:property name="autoStartup" value="false" />
		<beans:property name="outputChannel" ref="output" />
	</beans:bean>

</beans:beans>

The <channel id="output"/> element is defining the output channel for this module. This is followed by a bean definition for the class hello.Sample which accepts the channel as property "outputChannel". The "autoStartup" property is set to "false" to ensure that the module is initialized when the channels are established.

What To Change

Rename the template directory in modules/source/template/config and the template.xml file in this directory to match the name of your module.

On line 11, change "hello.ModuleTemplate" to match the name of your module class.