Spring Remoting Over JMS

JMS is one of the robust and widely used application integration style.
In this era of building loosely coupled service component based enterprise application; we often need to communicate with other application..exchange data...invoke operations.

Such inter JVM communication is made simpler and more robust by Spring's remoting support over JMS.
Its as simple as invoking a local object method.

Spring does it very transparently, with the help of JmsInvokerServiceExporter ,SimpleMessageListenerContainer and JmsInvokerProxyFactoryBean.
You just need to aware of these 3 classes and off course JMS connectionFactory and queue /topic definition.
First will define JMS related beans such as connectionFactory and Queue as follows:

<bean id="connectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">

        <property name="brokerURL" value="tcp://localhost:61616"/>

bean>

<bean id="salaryQueue" class="org.apache.activemq.command.ActiveMQQueue">

     <constructor-arg value="salaryCalculatorQueue"/>

 bean>


Now how to expose a pojo Calculator.java service for remoting over JMS using JMSInvokerServiceExporter

<bean id="calculatorService"    class="com.patkard.spring.remoting.service.impl.SalaryCalculator">

bean>

     

<bean id="remoteCalculatorService" class="org.springframework.jms.remoting.JmsInvokerServiceExporter">

        <property name="service" >

              <bean   class="com.patkard.spring.remoting.service.impl.SalaryCalculator">bean>

        property>

        <property name="serviceInterface"   value="com.patkard.spring.remoting.service.Calculator" />

bean>

Above JMSInvokerServiceExporter exposes Calculator service for remoting over JMS;  here you can also specific method which you wish to expose for remoting.

Define a listener for the queue and provide service bean reference for listener as follows

<bean class="org.springframework.jms.listener.SimpleMessageListenerContainer">

       <property name="connectionFactory" ref="connectionFactory"/>

       <property name="destination" ref="salaryQueue"/>

       <property name="concurrentConsumers" value="3"/>

       <property name="messageListener" ref="remoteCalculatorService"/>

   bean> 
On the client Side; there will be a JmsInvokerProxyFactoryBean definition which will invoke remote method / basically acts as event sender
 

<bean id="remoteCalculatorService" class="org.springframework.jms.remoting.JmsInvokerProxyFactoryBean">

     <property name="serviceInterface" value="com.patkard.spring.remoting.service.Calculator" />

     <property name="connectionFactory" ref="connectionFactory">property>

     <property name="queue" ref="salaryQueue">property>

 bean>          
 The connection Factory and Queue bean definitions are shared by both the client and server configurations


Before running client / server main programs ..start up Active MQ server.

write a simple main program to start up server like below..just load server side bean definitions

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:spring/remoting/jms/remoting-context-server.xml");

System.out.println("Started Server application...");

write simple client program..look up Calculator bean and invoke a method on bean as if your invoking a local object method.

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:spring/remoting/jms/remoting-context-client.xml");

Calculator calculator = (Calculator)applicationContext.getBean("remoteCalculatorService");

Employee employee = new Employee(12,”Dhananjay”);

employee.setGrade(1);

long sal = calculator.calculateSalary(employee);

System.out.println("Salary Returned "+sal);    
Simple isn't it?


Cheers,
Dhananjay