1.导入maven依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.20</version>
</dependency>

2.springmvc.xml配置

<mvc:annotation-driven>
    <mvc:message-converters register-defaults="true">
        <!-- 配置Fastjson支持 -->
        <bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">
            <property name="supportedMediaTypes">
                <list>
                    <value>application/json;charset=UTF-8</value>
                    <value>text/html;charset=UTF-8</value>
                </list>
            </property>
            <property name="features">
                <list>
                    <value>WriteMapNullValue</value>
                    <value>QuoteFieldNames</value>
                </list>
            </property>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

3.controller加上@responseBody即可

​
package cn.gson.spring.mvc3;

import java.net.URL;
import java.nio.charset.Charset;

import org.apache.commons.io.IOUtils;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import com.alibaba.fastjson.JSONObject;

@Controller
@RequestMapping("/json")
public class JsonController {

    @RequestMapping
    public String index() {
        return "info";
    }

    @RequestMapping("/load")
    @ResponseBody
    public User loadInfo() {
        User u = new User();
        u.setUserName("小贺");
        u.setPassword("123456");
        return u;
    }

}

​