How to leverage Spring Integration in a real-world JMS distributed architecture?

Question

For the following scenario I am looking for your advices and tips on best practices:

In a distributed (mainly Java-based) system with:

• many (different) client applications (web-app, command-line tools, REST API)
• a central JMS message broker (currently in favor of using ActiveMQ)
• multiple stand-alone processing nodes (running on multiple remote machines, computing expensive operations of different types as specified by the JMS message payload)

How would one best apply the JMS support provided by the Spring Integration framework to decouple the clients from the worker nodes? When reading through the reference documentation and some very first experiments it looks like the configuration of an JMS inbound adapter inherently require to use a subscriber, which in a decoupled scenario does not exist.

Small side note: communication should happen via JMS text messages (using a JSON data structure for future extensibility).

Answer 1

This doesn't really answer your question, but make sure you look into Apache Camel for connecting your different components. I found it extremely useful for connecting a JMS queue up to an existing web service and plan to use it for other components also.

An example that monitors an ActiveMQ queue for messages, transforms them, and posts them to a web service:

<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:camel="http://camel.apache.org/schema/spring"
   xsi:schemaLocation="
      http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
      http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring-2.3.0.xsd"&gt;

<bean id="callbackProcessor" class="com.package.CallbackProcessor"/>

<bean id="activemq" class="org.apache.camel.component.jms.JmsComponent">
    <property name="connectionFactory" ref="jmsFactory" />
</bean>

<camel:camelContext id="camel">
    <!-- Must put this in camel:endpoint because camel:from doesn't support property substitution -->
    <camel:endpoint id="callbackQueue" uri="activemq:queue:${jms.callback-queue-name}"/>
    <camel:route>
        <camel:from ref="callbackQueue"/>
        <camel:process ref="callbackProcessor"/>
        <camel:to uri="http://dummy"/&gt;&lt;!-- This will be replaced by the callbackProcessor with the callback URL in the message -->
    </camel:route>
</camel:camelContext>
</beans>

That's all that's necessary in our Spring application to fire up Camel and start processing messages.

Answer 2

Are you asking if Spring Integration can be used to implement a protocol bridge? Then the answer is yes, and does so quite simply.

Answer 3

Here is the Spring Integration I was coming up with today, if you find things which could be improved please follow up.

On the client side the messages can be send out and received through a SimpleMessagingGateway:

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

    <import resource="integration-common.xml"/>

    <!-- Communication Gateway for the Client (send/receive) -->
    <bean id="gateway" class="org.springframework.integration.gateway.SimpleMessagingGateway">
        <property name="requestChannel" ref="SenderChannel"/>
        <property name="replyChannel" ref="InboundChannel"/>
        <property name="replyTimeout" value="1000"/>
    </bean><!-- TODO: could use integration:gateway -->

    <!-- Sending out message to JMS request queue -->
    <integration:channel id="SenderChannel"/>
    <jms:outbound-channel-adapter
                        channel="SenderChannel" 
                        destination="requestQueue" />

    <!-- Listen to incoming messages on JMS reply queue -->
    <integration:channel id="InboundChannel">
        <integration:queue/>
    </integration:channel>
    <jms:message-driven-channel-adapter
            destination="replyQueue"
            channel="InboundChannel" />

</beans>

And the configuration on the processing node side looks like (please see the comments inline for more explanation of the Spring Integration elements):

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

    <import resource="integration-common.xml"/>

    <!-- Read in Message Endpoint Service Activator classes --> 
    <context:component-scan base-package="sample.integration.jmsbasic"/>

    <!-- Listen to incoming messages on the JMS request queue -->
    <integration:channel id="jmsinToProcChannel"/>
    <jms:message-driven-channel-adapter
            destination="requestQueue"
            channel="jmsinToProcChannel"/>

    <!-- Delegate message to service implementation and take care of answer -->
    <integration:service-activator 
            input-channel="jmsinToProcChannel" 
            ref="procService"
            output-channel="jmsBackChannel" />

    <!-- Send answer back to JMS reply queue -->
    <integration:channel id="jmsBackChannel"/>
    <jms:outbound-channel-adapter
                        channel="jmsBackChannel" 
                        destination="replyQueue" />

</beans>