问题:
在SpringMVC中使用Jackson实现json输出时配置如下:
<!-- 输出对象转JSON支持 --> <bean id="stringConverter" class="org.springframework.http.converter.StringHttpMessageConverter"> <property name="supportedMediaTypes"> <list> <value>text/plain;charset=UTF-8</value> </list> </property> </bean> <bean id="jsonConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"></bean> <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"> <property name="messageConverters"> <list> <ref bean="stringConverter"/> <ref bean="jsonConverter" /> </list> </property> </bean>
Maven 坐标情况如下:
<dependency> <groupId>org.apache.geronimo.specs</groupId> <artifactId>geronimo-servlet_2.5_spec</artifactId> <version>1.2</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-web</artifactId> <version>3.2.10.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>3.2.10.RELEASE</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.jaxrs</groupId> <artifactId>jackson-jaxrs-xml-provider</artifactId> <version>2.4.1</version> </dependency>
出现异常如下:
严重: Servlet /pcrm threw load() exception java.lang.ClassNotFoundException: org.codehaus.jackson.JsonProcessingException at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1718) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1569) at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2493) at java.lang.Class.getDeclaredConstructors(Class.java:1901) at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:231) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineConstructorsFromBeanPostProcessors(AbstractAutowireCapableBeanFactory.java:1003) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:976) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:487) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:293) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:290) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:191) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:633) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479) at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:651) at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:602) at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:665) at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:521) at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:462) at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136) at javax.servlet.GenericServlet.init(GenericServlet.java:158) at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1279) at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1192) at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1087) at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5210) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5493) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549) at java.util.concurrent.FutureTask.run(FutureTask.java:262) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:744)
一开始以为没有导入Jackson的Jar包,但排查后发现Maven坐标有了,Jar包也导入项目了,但还是一直错。于是我在导入的Jackson包中查找 org.codehaus.jackson.JsonProcessingException类,发现导入的Jackson包中,并不是org.codehaus的Jackson包,而是com.fasterxml的Jackson包。所以确定是Maven坐标导错了。
解决方案:
将
<dependency> <groupId>com.fasterxml.jackson.jaxrs</groupId> <artifactId>jackson-jaxrs-xml-provider</artifactId> <version>2.4.1</version> </dependency>
改成
<dependency> <groupId>org.codehaus.jackson</groupId> <artifactId>jackson-mapper-asl</artifactId> <version>1.9.4</version> </dependency>