我们已知道，controller 不支持直接返回对象，可将java对象，转为json对象，再返回。具体步骤如下

导入json包

<dependency>

<groupId>com.fasterxml.jackson.core</groupId>

<artifactId>jackson-databind</artifactId>

<version>2.9.8</version>

</dependency>
 

2、在springmvc.xml中配置 消息转换器和json乱码处理器

<mvc:annotation-driven>
    <mvc:message-converters register-defaults="true">
        <bean class="org.springframework.http.converter.StringHttpMessageConverter">
            <constructor-arg value="UTF-8"/>
        </bean>
        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <property name="objectMapper">
                <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                    <property name="failOnEmptyBeans" value="false"/>
                </bean>
            </property>
        </bean>
    </mvc:message-converters>

3、将Controller 方法中的java对象转换为json字符串，来返回

@RequestMapping("/a2")
public String ajaxtest(){
List<User> userList = new ArrayList<User>();
userList.add(new User("妗妗1",1,"男"));
userList.add(new User("妗妗12",2,"男"));
userList.add(new User("妗妗13",3,"男"));
User user4 = new User("妗妗14",1,"男");
System.out.println(userList); 

ObjectMapper mapper = new ObjectMapper();

//将值做为String 写出

String srt = mapper..writeValueAsString(userList);
return srt;