Spring MVC如何进行JSON数据的传输与接受

本篇文章写给刚接触SpingMVC的同道中人,虽然笔者本身水平也不高,但聊胜于无吧,希望可以给某些人带来帮助

笔者同时再次说明,运行本例时,需注意一些配置文件和网页脚本的路径，因为笔者的文件路径与读者的未必相同

首先准备以下 jar包:
commons-logging-1.1.3.jar
jackson-core-asl-1.9.2.jar
jackson-mapper-asl-1.9.2.jar
spring-aop-4.0.6.RELEASE.jar
spring-beans-4.0.6.RELEASE.jar
spring-context-4.0.6.RELEASE.jar
spring-core-4.0.6.RELEASE.jar
spring-expression-4.0.6.RELEASE.jar
spring-web-4.0.6.RELEASE.jar
spring-webmvc-4.0.6.RELEASE.jar
其中commons-logging-1.1.3.jar,jackson-core-asl-1.9.2.jar,jackson-mapper-asl-1.9.2.jar均可在struts2的工具包中取得

导入以上包后,去web.xml中进行配置,配置文件如下:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                             http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         id="WebApp_ID"
         version="3.1">
    <display-name>web</display-name>

    <!-- 配置springMVC请求分配Servlet -->
    <servlet>
        <servlet-name>springMVC</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!--
        <!-- 声明配置文件存放位置和配置文件的名称,加入不配置此标签,springMVC的配置文件名称默认为<servlet-name>的值加上"-servlet.xml",例如本例便是springMVC-servlet.xml -->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/*-servlet.xml</param-value>
        </init-param>
        -->
        <!-- 值小于1时,表示容器启动时并不加载此servlet,此时只有当第一次使用servlet时才会加载,但当值大于等于1时,表示容器启动时会立即加载此servlet,此时值越大表示加载的优先级越小 -->
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>springMVC</servlet-name>
        <!-- 请求链接以do结尾,具体怎么回事请耐心继续往下看 -->
        <url-pattern>*.do</url-pattern>
    </servlet-mapping>

    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>
</web-app>

接下来我们再看springMVC-servlet.xml,如下:

<?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: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.xsd
                           http://www.springframework.org/schema/context
                           http://www.springframework.org/schema/context/spring-context.xsd
                           http://www.springframework.org/schema/mvc
                           http://www.springframework.org/schema/mvc/spring-mvc.xsd">
    <!-- 扫描指定包下的所有类,倘若发现@Component,@Controller,@Service,@Repsitory等注解,则将相应的类实例化 -->
    <context:component-scan base-package="org.xt.controller"/>
    <!-- 配置视图资源 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <!-- 此乃视图资源的前缀 -->
        <property name="prefix" value="/WEB-INF/page"/>
        <!-- 此乃视图资源的后缀 -->
        <property name="suffix" value=".jsp"/>
    </bean>
    <!-- 此处乃进行json数据传输的关键,当配置 -->
    <bean id="jsonMapping" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"/>
    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
        <property name="messageConverters">
            <list>
                <ref bean="jsonMapping"/>
            </list>
        </property>
    </bean>
</beans>

接下来我们再看vo对象即值对象User.java,如下:

package org.xt.pojo;

import java.io.Serializable;

@SuppressWarnings("serial")
public class User implements Serializable {
    private long userId;
    private String userName;
    private String userPassword;

    public long getUserId() {
        return this.userId;
    }

    public void setUserId(long userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return this.userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPassword() {
        return this.userPassword;
    }

    public void setUserPassword(String userPassword) {
        this.userPassword = userPassword;
    }
}

好接下来便轮到了Controller的类TestJSONController.java,如下:

package org.xt.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.xt.pojo.User;

@Controller
@RequestMapping("/test")
public class TestJSONController {
    /*
     *看value属性,是以do结尾的,这正是web.xml配置url-pattern的值为*.do的原因,
     *这样所有的请求链接都必须以.do结尾,这样做的好处在于可以将请求链接同其他链接区分开来.
     *笔者建议如此做(当然了,你也可以将.do换成.html,.htm或者其他)
    */
    @RequestMapping(value = "/testJSON.do",method={RequestMethod.POST})
    @ResponseBody
    public User testJSON(@RequestBody User user) {
        System.out.println(user.getUserName() + " " + user.getUserPassword());
        return user;
    }
}

在以上类中出现的@ResponseBody和@RequestBody是关键,前者用于将JSON数据返回客户端,后者用于接受客户端的JSON数据

接下来我们来看看客户端的代码,客户端的代码由jquery完成

<%@ page language="java" contentType="text/html;charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
<title>TestJSONForSpringMVC</title>
</head>
<body>
    用户名:
    <input id="userName" type="text" style="width:150px" />
    <br />
    <br />
    密&nbsp;&nbsp;&nbsp;&nbsp;码:
    <input id="userPassword" type="password" style="width:150px" />
    <br />
    <br />
    <input id="login" type="button" value="登录" />
    <!-- 注意了,此处jquery的路径记得替换成你自己jquery所在的路径 -->
    <script type="text/javascript" src="jquery.js"></script>
    <script type="text/javascript">
        $("#login").click(function() {
            $.ajax({
                url : "test/testJSON.do",
                type : "POST",
                dataType : "json",
                contentType : "application/json;charset=UTF-8",
                data : JSON.stringify({
                    userId : "1",
                    userName : $("#userName").val(),
                    userPassword : $("#userPassword").val()
                }),
                success : function(result) {
                    alert(JSON.stringify(result));
                },
                error:function(result){
                    alert("Sorry,you are make a error!");
                }
            });
        });
    </script>
</body>
</html>

以上jsp文件中出现了一个JSON.stringify()函数,此函数由jquery提供,作用在于将JSON数据转换为字符串,之所以要这么做,原因在于服务端的@RequestBody只能识别字符串,而不能识别JSON对象

--写于2014-09-10 夜