It is also possible to expose services transparently using JMS as
the underlying communication protocol. The JMS remoting support in the
Spring Framework is pretty basic - it sends and receives on the
same thread and in the same
non-transactional Session, and
as such throughput will be very implementation dependent.
The following interface is used on both the server and the client side.
package com.foo; public interface CheckingAccountService { public void cancelAccount(Long accountId); }
The following simple implementation of the above interface is used on the server-side.
package com.foo; public class SimpleCheckingAccountService implements CheckingAccountService { public void cancelAccount(Long accountId) { System.out.println("Cancelling account [" + accountId + "]"); } }
This configuration file contains the JMS-infrastructure beans that are shared on both the client and server.
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="connectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory"> <property name="brokerURL" value="tcp://ep-t43:61616"/> </bean> <bean id="queue" class="org.apache.activemq.command.ActiveMQQueue"> <constructor-arg value="mmm"/> </bean> </beans>
On the server, you just need to expose the service object using
the JmsInvokerServiceExporter.
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="checkingAccountService" class="org.springframework.jms.remoting.JmsInvokerServiceExporter"> <property name="serviceInterface" value="com.foo.CheckingAccountService"/> <property name="service"> <bean class="com.foo.SimpleCheckingAccountService"/> </property> </bean> <bean class="org.springframework.jms.listener.SimpleMessageListenerContainer"> <property name="connectionFactory" ref="connectionFactory"/> <property name="destination" ref="queue"/> <property name="concurrentConsumers" value="3"/> <property name="messageListener" ref="checkingAccountService"/> </bean> </beans>
package com.foo; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Server { public static void main(String[] args) throws Exception { new ClassPathXmlApplicationContext(new String[]{"com/foo/server.xml", "com/foo/jms.xml"}); } }
The client merely needs to create a client-side proxy that will
implement the agreed upon interface
(CheckingAccountService). The resulting
object created off the back of the following bean definition can be
injected into other client side objects, and the proxy will take care of
forwarding the call to the server-side object via JMS.
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="checkingAccountService" class="org.springframework.jms.remoting.JmsInvokerProxyFactoryBean"> <property name="serviceInterface" value="com.foo.CheckingAccountService"/> <property name="connectionFactory" ref="connectionFactory"/> <property name="queue" ref="queue"/> </bean> </beans>
package com.foo; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Client { public static void main(String[] args) throws Exception { ApplicationContext ctx = new ClassPathXmlApplicationContext( new String[] {"com/foo/client.xml", "com/foo/jms.xml"}); CheckingAccountService service = (CheckingAccountService) ctx.getBean("checkingAccountService"); service.cancelAccount(new Long(10)); } }
You may also wish to investigate the support provided by the Lingo project, which (to quote the homepage blurb) “ ... is a lightweight POJO based remoting and messaging library based on the Spring Framework's remoting libraries which extends it to support JMS. ”