在Spring使用AWS SQS创建消息驱动Bean

在我之前的文章中，我展示了一个简单的示例，该示例如何将AWS SQS与Spring Framework结合使用以将消息放入队列中并从队列中读取消息。在本文中，我将更进一步，并使用Spring创建一个“消息驱动的Bean”，以便对放入队列中的每个消息都进行“自动”处理。 AWS在其文档页面上将其称为异步方式。要做到这一点，我将在Spring中定义一个MessageListener并将其配置为描述来听我的队列在这里。要查看初始项目设置，请参阅我的前一篇文章，因为在此不再赘述。

Spring应用程序上下文将定义消息侦听器（和相应的对象），如下所示：

<bean id="amazonMessageListener" class="net.pascalalma.aws.sqs.SpringMessageDrivenBean" /><bean id="messageListener" class="org.springframework.jms.listener.adapter.MessageListenerAdapter"><property name="delegate" ref="amazonMessageListener"/><property name="defaultListenerMethod" value="onMessage"/><property name="messageConverter"><null/></property></bean><bean id="jmsContainer" class="org.springframework.jms.listener.DefaultMessageListenerContainer"><property name="connectionFactory" ref="connectionFactory"/><property name="destinationName" ref="queueName" /><property name="messageListener" ref="messageListener" /></bean>

首先，我定义了我的MDB（MessageDrivenBean）bean，并将其称为“ amazonMessageListener”。接下来，我将此MDB用作“ messageListener”适配器的“代理”。这个“适配器” bean还可以负责转换消息有效负载（此处忽略）并在委托的侦听器中调用正确的方法。

在'jmsContainer'bean中，'adapter'与使用的JMS连接Factory和目标链接在一起。

剩下的就是MDB本身的源代码：

package net.pascalalma.aws.sqs;import org.apache.log4j.Logger;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.TextMessage;public class SpringMessageDrivenBean {final static Logger logger = Logger.getLogger(SpringMessageDrivenBean.class);public void onMessage(Message message) {if (message instanceof TextMessage) {try {logger.info(String.format("MDB received: %s ", ((TextMessage) message).getText()));}catch (JMSException ex) {throw new RuntimeException(ex);}}else {throw new IllegalArgumentException("Message must be of type TextMessage");}}
}

我认为这非常简单。对于放在队列中的每条消息，都会调用方法“ onMessage”，在这种情况下，它仅打印消息的文本内容。为了查看它的工作原理，我使用下面的“ main”类：

package net.pascalalma.aws.sqs;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;public class SpringMdbMain {public static void main(String[] args) {//Build application context by reading spring-config.xmlApplicationContext ctx = new ClassPathXmlApplicationContext(new String[]{"application-context.xml"});//Get an instance of ProviderService class;MyMessageProvider prdSvc = (MyMessageProvider) ctx.getBean("myMessageProviderService");//Call getProduct method of ProductServiceprdSvc.sendMessage("This is a test A");prdSvc.sendMessage("This is a test B");prdSvc.sendMessage("This is a test C");prdSvc.sendMessage("This is a test D");}
}

结果为以下输出：

2015-04-11 13:17:20 DEBUG net.pascalalma.aws.sqs.MyMessageProvider(23) - Sending message with txt: This is a test A
2015-04-11 13:17:26 DEBUG net.pascalalma.aws.sqs.MyMessageProvider(36) - Message sent 
2015-04-11 13:17:26 DEBUG net.pascalalma.aws.sqs.MyMessageProvider(23) - Sending message with txt: This is a test B
2015-04-11 13:17:26 INFO  net.pascalalma.aws.sqs.SpringMessageDrivenBean(16) - MDB received: This is a test A 
2015-04-11 13:17:26 DEBUG net.pascalalma.aws.sqs.MyMessageProvider(36) - Message sent 
2015-04-11 13:17:26 DEBUG net.pascalalma.aws.sqs.MyMessageProvider(23) - Sending message with txt: This is a test C
2015-04-11 13:17:26 INFO  net.pascalalma.aws.sqs.SpringMessageDrivenBean(16) - MDB received: This is a test B 
2015-04-11 13:17:27 DEBUG net.pascalalma.aws.sqs.MyMessageProvider(36) - Message sent 
2015-04-11 13:17:27 DEBUG net.pascalalma.aws.sqs.MyMessageProvider(23) - Sending message with txt: This is a test D
2015-04-11 13:17:27 INFO  net.pascalalma.aws.sqs.SpringMessageDrivenBean(16) - MDB received: This is a test C 
2015-04-11 13:17:27 DEBUG net.pascalalma.aws.sqs.MyMessageProvider(36) - Message sent 
2015-04-11 13:17:27 INFO  net.pascalalma.aws.sqs.SpringMessageDrivenBean(16) - MDB received: This is a test D