前言

? ? ?目前前后端分離后，接口大多數返回給前端的都是json數據，那么我嘗試用SpringMVC4的Controller返回json。demo過程中遇到了幾個問題寫出來和java初學者分享一下。

開發環境

? ? idea2016、jdk1.8、tomcat7

? ? SpringMVC4、jackson2.5

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開發問題

? ? 1、SpringMVC4如果想返回json的話可以使用ResponseBody、ResponseEntity注解，如果你打算返回注解而沒有引用json處理jar包，訪問http://localhost:8080/rest/users時會提示http 406。

? ? 2、SpringMVC4版本后json序列化必須使用jackson相關，jackson-annotations-2.5.0.jar，jackson-core-2.5.0.jar，jackson-databind-2.5.0.jar。我開始用的fastjson但會報錯：

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

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項目配置文件

? ? 初學Spring，配置文件是最煩神的，概括看來首先下載jar包，你需要關注pom.xml、其次是web.xml、spring-mvc.xml。

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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>

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2、web.xml

<web-app><display-name>Archetype Created Web Application</display-name><!-- Spring監聽 --><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"><!-- 注解驅動 --><mvc:annotation-driven /><!-- 掃描包 --><context:component-scan base-package="com.autohome.controller" /><!-- 視圖解析 --><bean class="org.springframework.web.servlet.view.UrlBasedViewResolver"><!-- 返回的視圖模型數據需要經過jstl來處理 --><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， 可以編寫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);}}

　　

? ?輸入http://localhost:8080/rest/users、http://localhost:8080/rest/user/1/ ?，第一個SpringMVC demo搞定。

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轉載于:https://www.cnblogs.com/sword-successful/p/6402562.html

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