java - JmsTemplate 中的空指针异常？

Question

我已经尝试运行简单的 spring jmstemplate 示例。这里是发件人的源代码，

import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.Session;
import javax.jms.TextMessage;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.jms.core.MessageCreator;

public class MessageSender {

    @Autowired
    private JmsTemplate jmsTemplate;

    public void setJmsTemplate(JmsTemplate jmsTemplate)
    {
        this.jmsTemplate = jmsTemplate;
    }
    public void sendMessage()
    {
        jmsTemplate.send(new MessageCreator() {
            public Message createMessage(Session session)
            {
                TextMessage message = null;
                try
                {
                    message = session.createTextMessage();
                    message.setStringProperty("text", "Hello World");
                }
                catch (JMSException e)
                {
                    e.printStackTrace();
                }
                return message;
        }
    });
    }
}

这里是用于集成 spring 和 jmstemplate 的配置文件。

<?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:tx="http://www.springframework.org/schema/tx"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop"  
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
                        http://www.springframework.org/schema/tx 
                        http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
                        http://www.springframework.org/schema/mvc
                        http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd                        
                        http://www.springframework.org/schema/context
                        http://www.springframework.org/schema/context/spring-context-3.0.xsd
                        http://www.springframework.org/schema/aop 
                        http://www.springframework.org/schema/aop/spring-aop-2.5.xsd">

    <!-- Spring AOP -->
    <context:component-scan base-package="com.test"/>
    <aop:aspectj-autoproxy />
    <bean id="messageListener" class="com.test.QueuereceiverDB" />   

    <bean id="jndiTemplate" class="org.springframework.jndi.JndiTemplate">
        <property name="environment">
            <props>
                <prop key="java.naming.provider.url">jnp://localhost:1099</prop>
                <prop key="java.naming.factory.url.pkgs">org.jnp.interfaces:org.jboss.naming</prop>
                <prop key="java.naming.factory.initial">org.jnp.interfaces.NamingContextFactory</prop>
            </props>
        </property>
    </bean>

    <bean id="queueConnectionFactory" class="org.springframework.jndi.JndiObjectFactoryBean">
        <property name="jndiTemplate">
            <ref bean="jndiTemplate" />
        </property>
        <property name="jndiName">
            <value>ConnectionFactory</value>
        </property>
    </bean>

    <bean id="jmsDestinationResolver" class="org.springframework.jms.support.destination.JndiDestinationResolver">
        <property name="jndiTemplate">
            <ref bean="jndiTemplate" />
        </property>
        <property name="cache">
            <value>true</value>
        </property>
    </bean>

    <bean id="QueueTemplate" class="org.springframework.jms.core.JmsTemplate">
        <property name="connectionFactory">
            <ref bean="queueConnectionFactory" />
        </property>
        <property name="destinationResolver">
            <ref bean="jmsDestinationResolver" />
        </property>
    </bean>
    <bean id="jmsSender" class="com.test.MessageSender">
        <property name="jmsTemplate"> <ref bean="QueueTemplate" />
        </property>

    </bean>

    <bean id="Queue" class="org.springframework.jndi.JndiObjectFactoryBean">
        <property name="jndiTemplate"> <ref bean="jndiTemplate" />
        </property>
        <property name="jndiName">
            <value>queue/MyQueue</value>
        </property>
    </bean>
    <!-- JmsTemplate Definition -->
    <bean id="jmsTemplate" class="org.springframework.jms.core.JmsTemplate">
        <property name="connectionFactory" ref="queueConnectionFactory" />
         <property name="defaultDestination" ref="Queue" /> 
    </bean>
    <bean id="jmscontainer" class="org.springframework.jms.listener.DefaultMessageListenerContainer">
        <property name="concurrentConsumers" value="5" />
        <property name="connectionFactory" ref="queueConnectionFactory" />
        <property name="destination" ref="Queue" />
        <property name="messageListener" ref="messageListener" />
    </bean> 

</beans>

如果我运行下面的例子是相应的stacktrace

SEVERE [com.sun.jersey.spi.container.ContainerResponse] The RuntimeException could not be mapped to a response, re-throwing to the HTTP container: java.lang.NullPointerException
    at com.test.MessageSender.sendMessage(MessageSender.java:30) [:]
    at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149) [:]
    at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:689) [:3.1.0.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150) [:3.1.0.RELEASE]
    at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:55) [:3.1.0.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161) [:3.1.0.RELEASE]
    at org.springframework.aop.framework.adapter.AfterReturningAdviceInterceptor.invoke(AfterReturningAdviceInterceptor.java:50) [:3.1.0.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161) [:3.1.0.RELEASE]
    at org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke(MethodBeforeAdviceInterceptor.java:50) [:3.1.0.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161) [:3.1.0.RELEASE]
    at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:80) [:3.1.0.RELEASE]

调试代码后，我发现问题出在哪里，jmsTemplate.send(new MessageCreator() {执行此行时将显示空指针。

我想我们需要从 xml 文件初始化 jmstemplate。但我不知道如何实现这个？请有人帮助我。

我在以下文件中配置了队列，该文件将放置在 jboss/server/default/server 文件夹中mdb-hornetq-xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="urn:hornetq"
    xsi:schemaLocation="urn:hornetq /schema/hornetq-jms.xsd" >

    <queue name="MyQueue2" >
        <entry name="/queue/MyQueue" />
    </queue>

</configuration> 

Answer 1

我发现您声明了两个 JmsTemplate bean 很奇怪。我有一个更简单的配置。涉及到两个JNDI名称，一个是目的地(队列)名称，一个是连接工厂名称。

假设您的队列是 MyQueue 并且您的连接工厂是 MyCF。要发送消息，您只需要声明两个 spring bean:

<bean id="jmsConnectionFactory" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="MyCF"/>
    <property name="lookupOnStartup" value="false"/>
    <property name="cache" value="true"/>
    <property name="proxyInterface" value="javax.jms.ConnectionFactory"/>
</bean>

<bean name="jmsTemplate" class="org.springframework.jms.core.JmsTemplate">
    <property name="connectionFactory">
        <ref bean="jmsConnectionFactory"/>
    </property>
    <property name="defaultDestinationName" value="MyQueue" /> 
</bean> 

发件人类中的源代码将包含:

@Autowired
private JmsTemplate jmsTemplate;

private void sendTextMessage(final String message)
    MessageCreator messageCreator = new MessageCreator() {
        @Override
        public Message createMessage(Session session) throws JMSException {
            return session.createTextMessage(message);
        }
    };
    jmsTemplate.send(messageCreator);
}

缺少的是que connection factory和queue的HornetQ配置。该配置定义了 JNDI 名称。在我的例子中，HornetQ 与 JBoss Application Server 一起运行。因此，我在 JBoss AS 配置中配置了连接工厂和队列(例如，在 standalone.xml 文件中)。以下是片段:

<pooled-connection-factory name="hornetq-local">
    <transaction mode="local"/>
    <connectors>
        <connector-ref connector-name="in-vm"/>
    </connectors>
    <entries>
        <entry name="java:/MyCF"/>
    </entries>
</pooled-connection-factory>

<jms-destinations>
    <jms-queue name="MyQueue">
        <entry name="java:jboss/queues/a/b/SomeQueue"/>
        <durable>true</durable>
    </jms-queue>
</jms-destinations>

我相信您在独立模式下使用 HornetQ。将这些设置映射到那里的工厂和队列配置应该很容易。