SpringMVC4返回json

前言

目前前后端分离后，接口大多数返回给前端的都是json数据，那么我尝试用SpringMVC4的Controller返回json。demo过程中遇到了几个问题写出来和java初学者分享一下。

开发环境

idea2016、jdk1.8、tomcat7

SpringMVC4、jackson2.5

开发问题

1、SpringMVC4如果想返回json的话可以使用ResponseBody、ResponseEntity注解，如果你打算返回注解而没有引用json处理jar包，访问http://localhost:8080/rest/users时会提示http 406。

2、SpringMVC4版本后json序列化必须使用jackson相关，jackson-annotations-2.5.0.jar，jackson-core-2.5.0.jar，jackson-databind-2.5.0.jar。我开始用的fastjson但会报错：

Java.lang.NoClassDefFoundError: com/fasterxml/jackson/core/JsonProcessingException

项目配置文件

初学Spring，配置文件是最烦神的，概括看来首先下载jar包，你需要关注pom.xml、其次是web.xml、spring-mvc.xml。

1、pom.xml

 <dependencies><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>3.8.1</version><scope>test</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-core</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-oxm</artifactId><version>${spring.version}</version></dependency><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.12</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>2.5.0</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId><version>2.5.0</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.5.0</version></dependency></dependencies>

2、web.xml

<web-app><display-name>Archetype Created Web Application</display-name><!-- Spring监听 --><listener><listener-class>org.springframework.web.context.ContextLoaderListener</listener-class></listener><context-param><param-name>contextConfigLocation</param-name><param-value>classpath:applicationContext.xml</param-value></context-param><servlet><servlet-name>MVC</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><param-name>contextConfigLocation</param-name><param-value>classpath:spring-mvc.xml</param-value></init-param><load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>MVC</servlet-name><url-pattern>/</url-pattern></servlet-mapping></web-app>

3、spring-mvc.xml

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:mvc="http://www.springframework.org/schema/mvc"xmlns:beans="http://www.springframework.org/schema/beans"xmlns:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/mvchttp://www.springframework.org/schema/mvc/spring-mvc.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd"><!-- 注解驱动 --><mvc:annotation-driven /><!-- 扫描包 --><context:component-scan base-package="com.autohome.controller" /><!-- 视图解析 --><bean class="org.springframework.web.servlet.view.UrlBasedViewResolver"><!-- 返回的视图模型数据需要经过jstl来处理 --><property name="viewClass"value="org.springframework.web.servlet.view.JstlView" /><property name="prefix" value="/WEB-INF/views/" /><property name="suffix" value=".jsp" /></bean><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.MappingJackson2HttpMessageConverter"></bean><beanclass="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"><property name="messageConverters"><list><ref bean="stringConverter" /><ref bean="jsonConverter" /></list></property></bean></beans>

OK，可以编写rest controller了。

@Controller
@RequestMapping("/rest")
public class RestController {@RequestMapping(value="/sayHello",method = RequestMethod.GET)public @ResponseBodyString sayHello(){return "{\"returncode\":0,\"message\":\"hello world\"}";}@RequestMapping(value="/users")public ResponseEntity<List<User>> listAllUser(){List<User> list =new ArrayList<User>();User user =new User();user.setId(1);user.setName("test");user.setAge(30);User user2 =new User();user2.setId(2);user2.setName("test1");user2.setAge(30);list.add(user);list.add(user2);return new ResponseEntity<List<User>>(list, HttpStatus.OK);}@RequestMapping(value="/user/{id}",method = RequestMethod.GET)public ResponseEntity<User> getUser(@PathVariable long id){System.out.println("id:"+id);User user =new User();user.setId(1);user.setName("test");user.setAge(30);return new ResponseEntity<User>(user,HttpStatus.OK);}}

输入http://localhost:8080/rest/users、http://localhost:8080/rest/user/1/ ，第一个SpringMVC demo搞定。

转载于:https://www.cnblogs.com/sword-successful/p/6402562.html