在mvc spring中向activemq发送消息给出空指针异常

时间：2017-12-12 18:56:00

标签： spring-mvc activemq

我尝试通过mvc spring执行示例发送和从activemq重新发送消息但是当我运行项目时出现此错误：

java.lang.NullPointerException
    com.sarf.jms.MessageProducerBean.sendMessage(MessageProducerBean.java:24)
    com.sarf.testactimq.HomeController.home(HomeController.java:42)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:497)
    org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

我的源代码：

MessageObject.java：

package com.sarf.data; 

public class MessageObject {
  private String mailId;
  private String message;

 public MessageObject(){}; 
 public MessageObject(String mailId, String message) {
  super();
  this.mailId = mailId;
  this.message = message;
 }
 public String getMailId() {
  return mailId;
 }
 public void setMailId(String mailId) {
  this.mailId = mailId;
 }
 public String getMessage() {
  return message;
 }
 public void setMessage(String message) {
  this.message = message;
 }
}

MessageConsumerBean.java：

package com.sarf.jms;

import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.MapMessage;

import org.springframework.jms.core.JmsTemplate;
import org.springframework.jms.support.JmsUtils;
import com.sarf.data.MessageObject;

public class MessageConsumerBean{

     private JmsTemplate jmsTemplate;
     private Destination destination;

     public void setJmsTemplate(JmsTemplate jmsTemplate) {
         this.jmsTemplate = jmsTemplate;
     }
     public void setDestination(Destination destination) {
         this.destination = destination;
     }

     public MessageObject receiveMessage() {
      MapMessage message = (MapMessage) jmsTemplate.receive(destination);
      try {
           MessageObject messageObj = new MessageObject();
           messageObj.setMailId(message.getString("mailId"));
           messageObj.setMessage(message.getString("message"));
           return messageObj;
           } catch (JMSException e) {
             throw JmsUtils.convertJmsAccessException(e);
           }
       }
    }

MessageProducerBean.java：

package com.sarf.jms;
import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.MapMessage;
import javax.jms.Message;
import javax.jms.Session;

import org.springframework.jms.core.JmsTemplate;
import org.springframework.jms.core.MessageCreator;
import com.sarf.data.MessageObject;

public class MessageProducerBean {

     //JMS Template object
     private JmsTemplate jmsTemplate;
     private Destination destination;
     public void setJmsTemplate(JmsTemplate jmsTemplate) {
         this.jmsTemplate = jmsTemplate;
     }
     public void setDestination(Destination destination) {
         this.destination = destination;
     }
     public void sendMessage(final MessageObject messageObj) {
      jmsTemplate.send(destination, new MessageCreator() {
      public Message createMessage(Session session) throws JMSException {
            MapMessage message = session.createMapMessage();
            message.setString("mailId", messageObj.getMailId());
            message.setString("message", messageObj.getMessage());
            return message;
           }
      }); //send method close here
     }//method ends here 
    }

家庭控制器：

package com.sarf.testactimq;

import java.text.DateFormat;

import java.util.Date;
import java.util.Locale;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import com.sarf.data.MessageObject;
import com.sarf.jms.MessageProducerBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.sarf.jms.*;

/**
 * Handles requests for the application home page.
 */
@Controller
public class HomeController {

    private static final Logger logger = LoggerFactory.getLogger(HomeController.class);

    /**
     * Simply selects the home view to render by returning its name.
     */
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String home(Locale locale, Model model) {
        logger.info("Welcome home! The client locale is {}.", locale);

        Date date = new Date();
        DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, locale);

        String formattedDate = dateFormat.format(date);

        model.addAttribute("serverTime", formattedDate );
         MessageProducerBean mp = new MessageProducerBean();
         mp.sendMessage(new MessageObject("1234", "Test Message"));
            /*
         MessageConsumerBean mc = new MessageConsumerBean();
                MessageObject messageObj = mc.receiveMessage();
                System.out.println("Message from " + 
                 messageObj.getMailId() + " received");
        */
        return "home";
    }

}

servlete_context.xml：

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure -->

    <!-- Enables the Spring MVC @Controller programming model -->
    <annotation-driven />

    <!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory -->
    <resources mapping="/resources/**" location="/resources/" />

    <!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory -->
    <beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <beans:property name="prefix" value="/WEB-INF/views/" />
        <beans:property name="suffix" value=".jsp" />
    </beans:bean>

             <beans:bean id="connectionFactory"
        class="org.apache.activemq.ActiveMQConnectionFactory">
        <beans:property name="brokerURL" value="tcp://localhost:61616" />
    </beans:bean>

    <beans:bean id="mailDestination"
        class="org.apache.activemq.command.ActiveMQQueue">
        <beans:constructor-arg value="mail.queue" />
    </beans:bean>

    <beans:bean id="jmsTemplate"
        class="org.springframework.jms.core.JmsTemplate">
        <beans:property name="connectionFactory" ref="connectionFactory" />
    </beans:bean>

    <beans:bean id="producer"
        class="com.sarf.jms.MessageProducerBean">
        <beans:property name="destination" ref="mailDestination" />
        <beans:property name="jmsTemplate" ref="jmsTemplate" />
    </beans:bean>
     <beans:bean id="consumer"
        class="com.sarf.jms.MessageConsumerBean">
        <beans:property name="destination" ref="mailDestination" />
        <beans:property name="jmsTemplate" ref="jmsTemplate" />
    </beans:bean>

    <context:component-scan base-package="com.sarf.testactimq" />



</beans:beans>

root_context.xml：

<?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.xsd">

    <!-- Root Context: defines shared resources visible to all other web components -->
             <bean id="connectionFactory"
        class="org.apache.activemq.ActiveMQConnectionFactory">
        <property name="brokerURL" value="tcp://localhost:61616" />
    </bean>

    <bean id="mailDestination"
        class="org.apache.activemq.command.ActiveMQQueue">
        <constructor-arg value="mail.queue" />
    </bean>

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

    <bean id="producer"
        class="com.sarf.jms.MessageProducerBean">
        <property name="destination" ref="mailDestination" />
        <property name="jmsTemplate" ref="jmsTemplate" />
    </bean>
     <bean id="consumer"
        class="com.sarf.jms.MessageConsumerBean">
        <property name="destination" ref="mailDestination" />
        <property name="jmsTemplate" ref="jmsTemplate" />
    </bean>
</beans>

pom.xml：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.sarf</groupId>
    <artifactId>testactimq</artifactId>
    <name>testmessage</name>
    <packaging>war</packaging>
    <version>1.0.0-BUILD-SNAPSHOT</version>
    <properties>
        <java-version>1.6</java-version>
        <org.springframework-version>3.1.1.RELEASE</org.springframework-version>
        <org.aspectj-version>1.6.10</org.aspectj-version>
        <org.slf4j-version>1.6.6</org.slf4j-version>
    </properties>
    <dependencies>

    <dependency>
      <groupId>org.apache.activemq</groupId>
      <artifactId>activemq-all</artifactId>
      <version>5.13.3</version>
   </dependency>
        <!-- Spring -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${org.springframework-version}</version>
            <exclusions>
                <!-- Exclude Commons Logging in favor of SLF4j -->
                <exclusion>
                    <groupId>commons-logging</groupId>
                    <artifactId>commons-logging</artifactId>
                 </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <!-- AspectJ -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${org.aspectj-version}</version>
        </dependency>   

        <!-- Logging -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${org.slf4j-version}</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>jcl-over-slf4j</artifactId>
            <version>${org.slf4j-version}</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>${org.slf4j-version}</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.15</version>
            <exclusions>
                <exclusion>
                    <groupId>javax.mail</groupId>
                    <artifactId>mail</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>javax.jms</groupId>
                    <artifactId>jms</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>com.sun.jdmk</groupId>
                    <artifactId>jmxtools</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>com.sun.jmx</groupId>
                    <artifactId>jmxri</artifactId>
                </exclusion>
            </exclusions>
            <scope>runtime</scope>
        </dependency>

        <!-- @Inject -->
        <dependency>
            <groupId>javax.inject</groupId>
            <artifactId>javax.inject</artifactId>
            <version>1</version>
        </dependency>

        <!-- Servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

        <!-- Test -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.7</version>
            <scope>test</scope>
        </dependency>        
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <artifactId>maven-eclipse-plugin</artifactId>
                <version>2.9</version>
                <configuration>
                    <additionalProjectnatures>
                        <projectnature>org.springframework.ide.eclipse.core.springnature</projectnature>
                    </additionalProjectnatures>
                    <additionalBuildcommands>
                        <buildcommand>org.springframework.ide.eclipse.core.springbuilder</buildcommand>
                    </additionalBuildcommands>
                    <downloadSources>true</downloadSources>
                    <downloadJavadocs>true</downloadJavadocs>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.5.1</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                    <compilerArgument>-Xlint:all</compilerArgument>
                    <showWarnings>true</showWarnings>
                    <showDeprecation>true</showDeprecation>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.2.1</version>
                <configuration>
                    <mainClass>org.test.int1.Main</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

由于调用在我的控制器中调用的MessageProducerBean中定义的methode sendMessage导致的运行时错误，我运行我的activemq，如下图所示： enter image description here 注意：我使用的是带有tc服务器和activemq版本5.13.3的spring suite工具  那我有什么不对的帮助呢？

1 个答案:

答案 0 :(得分：0)

在HomeController中您正在创建MessageProducerBean，如此：

MessageProducerBean mp = new MessageProducerBean();

然后立即使用MessageProducerBean发送消息：

mp.sendMessage(new MessageObject("1234", "Test Message"));

但是，此时MessageProducerBean正在尝试使用您尚未初始化的jmsTemplate变量，因此它null。因此，您会收到java.lang.NullPointerException。

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