为什么jmsTemplate总是为null?使用spring和Apache ActiveMQ [英] Why is jmsTemplate always null? Using spring and Apache ActiveMQ

问题描述

我对Spring和JMS还是很陌生.我一直在尝试提出一个涉及activemq和Spring的实现，如下所示.

Im very new to Spring and JMS. Ive been trying to come up with an implementation that involves activemq and Spring as follows.

spring-context.xml
<bean id="sampleApacheConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory" lazy-init="true">
    <property name="brokerURL" value="tcp://localhost:61616"/>
    <property name="userName" value="kodeseeker"/>
    <property name="password" value="mypassword"/>

</bean>

 <bean id="connectionFactory" class="org.springframework.jms.connection.CachingConnectionFactory">
        <constructor-arg ref="sampleApacheConnectionFactory" />
    </bean>

    <!--  Default Destination Queue Definition-->
    <bean id="defaultDestination" class="org.apache.activemq.command.ActiveMQQueue">
        <constructor-arg index="0" value="test.Foo"/>
    </bean>

    <!-- JmsTemplate Definition -->
    <bean id="jmsTemplate" class="org.springframework.jms.core.JmsTemplate">
        <property name="connectionFactory" ref="connectionFactory" />
        <property name="defaultDestination" ref="defaultDestination" />
    </bean>

    <!-- Message Sender Definition -->
    <bean id="messageSender" class="com.mypackage.Publisher2">
    </bean>

<!-- Message Receiver Definition -->
    <bean id="messageReceiver" class="com.mypackage.Listener">

    </bean>
       <bean class="org.springframework.jms.listener.SimpleMessageListenerContainer">
        <property name="connectionFactory" ref="connectionFactory" />
        <property name="destinationName" value="test.Foo" />
        <property name="messageListener" ref="messageReceiver" />
    </bean>

</beans>

Publisher2.java

Publisher2.java

public class Publisher2 {

 @Autowired
 protected JmsTemplate jmsTemplate;
 .......
// function called to perform update.
  public void publishUpdate(final CustomMessage payload) throws JMSException {
      LOGGER.entry();
      try {
          JmsTemplate jmsTemp= this.jmsTemplate;
          if(jmsTemp ==null){
        //jmsTemplate is ALWAYS null.
           LOGGER.error("Jms Template is never initialized!!");
           return;
          }
          jmsTemp.send(new MessageCreator(){
         @Override
         public Message createMessage(Session session) throws JMSException {
             Message message = message(payload,session);    
             LOGGER.info("Sending message");
             return message;
        }
        });
      } catch (Exception jmsExcpetion) {
          LOGGER.error("Error placing message on Queue",jmsExcpetion);
     
      }
      LOGGER.exit();
  }
}

要初始化jmsTemplate，我需要专门做什么吗?如果有必要，我很乐意提供更多详细信息.

Is there anything I specifically need to do in order to initialize jmsTemplate? Id be happy to provide any more details if necessary .

修改1: 调用publishupdate

public class UpdateHandlerImpl implements UpdateHandler {
    private final Publisher2 publisher;
    ....
    public UpdateHandlerImpl() {
        this(new Publisher2());
    }
    public UpdateHandlerImpl(
            final Publisher2 publisher) {
           this. publisher = publisher;
    }
    ....
    @Override
    public void  handle(final CustomMessage entity) {
        try {
                     publisher. publishUpdate(entity);
        } catch (final JMSException e) {
            LOGGER.error("Error sending message", e);
        }

            }
   …..
    }

修改3: 根据@keith的输入更新了UpdateHandlerImpl的版本

Edit 3: Updated version of UpdateHandlerImpl based on @keith's input

public class UpdateHandlerImpl implements UpdateHandler {
    //Hoping spring wires this?
    Publisher2 publisher;
    @Override
    public void  handle(final CustomMessage entity) {
        try {
                     publisher. publishUpdate(entity);
        } catch (final JMSException e) {
            LOGGER.error("Error sending message", e);
        }

            }
   …..
    }

修改2: 使用以下注释，在启动时通过mule(这是一个mule应用程序)加载spring上下文.

Edit 2: The spring context is loaded through mule( this is a mule application) on startup using the following annotation.

<spring:beans>
        <spring:import resource="classpath:spring-context.xml" />
    </spring:beans>

推荐答案

如果使用new创建Publisher2，则将不会在创建的实例上关联依赖项.而是在上下文文件中将其定义为Spring bean，然后从那里获取它.

If you are creating Publisher2 using new, you will not have the dependencies wired on the instance you create. Instead, define it as a Spring bean in your context file and get it from there.

这是我所怀疑的，在您对问题的最新更新中，您确认您正在使用新内容创建Publisher2.

It's as I suspected, in your latest update to the question you confirmed that you are creating a Publisher2 with new.

public UpdateHandlerImpl() {
        this(new Publisher2());
    }

这不是Spring的工作方式.参见第6.3.2节有关实例化bean的Spring Framework文档. (简而言之，使用上下文创建Bean)

This is not how Spring works. See Section 6.3.2 of the Spring Framework documentation on instantiating beans. (In short, create the bean using the context)

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