【SpringMVC】(七)JSON

JSON

JSON（JavaScript Object Notation，JS对象标记）是一种轻量级的数据交换格式。

1.JSON和JavaScript对象互转

JSON转JS对象

var obj = JSON.parse('{"a":"Hello","b":"World"}');
//结果是 {a:'Hello',b:'World'}

JS对象转JSON

var json = JSON.stringify({a:'Hello',b:'World'});
//结果是 '{"a":"Hello","b":"World"}'

2.Controller 返回JSON数据

测试环境搭建

导入依赖

<dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
            <scope>provided</scope>
</dependency>

springmvc配置文件

<?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
       https://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/mvc
       https://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!--自动扫描包，让指定包下的注解生效，由IOC容器统一管理-->
    <context:component-scan base-package="com.musecho.controller"/>

    <!-- 视图解析器 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
          id="internalResourceViewResolver">
        <!--前缀-->
        <property name="prefix" value="/WEB-INF/jsp/" />
        <!--后缀-->
        <property name="suffix" value=".jsp" />
    </bean>
</beans>

User

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private String name;
    private int age;
    private String sex;
}

UserController

@Controller
public class UserController {

    @RequestMapping("/j1")
    @ResponseBody //加上这个注解，就不会走视图解析器，直接返回一个字符串
    public String json1(){
        User user = new User("zkk 1号",14,"女");

        return user.toString();
    }
}

@ResponseBody ：方法上方加这个注解，就不会走视图解析器，直接返回一个字符串
@RestController：类上方加这个注解，该类里所有的方法都不会走视图解析器，直接返回字符串。

（一）使用Jackson（json解析工具）

导入依赖

<dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.12.1</version>
</dependency>

返回一个对象

@RequestMapping("/j1")
@ResponseBody
public String json1() throws JsonProcessingException {
        User user = new User("zkk 1号", 14, "女");

        //jackson的ObjectMapper
        ObjectMapper mapper = new ObjectMapper();
        String str = mapper.writeValueAsString(user);

        return str;
}

返回集合

	@RequestMapping("/j2")
    @ResponseBody
    public String json2() throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();

        List<User> userList = new ArrayList<User>();
        User user1 = new User("zkk 1号", 14, "女");
        User user2 = new User("zkk 2号", 14, "女");
        User user3 = new User("zkk 3号", 14, "女");
        User user4 = new User("zkk 4号", 14, "女");
        User user5 = new User("zkk 5号", 14, "女");
        userList.add(user1);
        userList.add(user2);
        userList.add(user3);
        userList.add(user4);

        String str=mapper.writeValueAsString(userList);
        return str;
    }

返回日期时间

1.使用java的方法格式化

 	@RequestMapping("/j3")
    @ResponseBody
    public String json3() throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();

        Date date =new Date();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        //ObjectMapper,时间解析后的默认格式为：Timestamp，时间戳
        return mapper.writeValueAsString(sdf.format(date));
    }

2.使用ObjectMapper的方法格式化

@RequestMapping("/j3")
@ResponseBody
public String json4() throws JsonProcessingException {

   ObjectMapper mapper = new ObjectMapper();

   //不使用时间戳的方式
   mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
   //自定义日期格式对象
   SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   //指定日期格式
   mapper.setDateFormat(sdf);

   Date date = new Date();
   String str = mapper.writeValueAsString(date);

   return str;
}

抽象成一个json工具类

public class JsonUtils {

    public static String getJson(Object object) throws JsonProcessingException {
        return getJson(object, "yyyy-MM-dd HH:mm:ss");
    }

    public static String getJson(Object object, String dateFormat) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
	
        mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
        SimpleDateFormat sdf = new SimpleDateFormat(dateFormat);
        mapper.setDateFormat(sdf);

        return mapper.writeValueAsString(object);
    }

}

使用工具类后的方法

	@RequestMapping(value = "/j1")
    @ResponseBody
    public String json1() throws JsonProcessingException {
        User user = new User("zkk 1号", 14, "女");

        return JsonUtils.getJson(user);
    }

    @RequestMapping("/j2")
    @ResponseBody
    public String json2() throws JsonProcessingException {
        List<User> userList = new ArrayList<User>();
        User user1 = new User("zkk 1号", 14, "女");
        User user2 = new User("zkk 2号", 14, "女");
        User user3 = new User("zkk 3号", 14, "女");
        User user4 = new User("zkk 4号", 14, "女");
        User user5 = new User("zkk 5号", 14, "女");
        userList.add(user1);
        userList.add(user2);
        userList.add(user3);
        userList.add(user4);

        return JsonUtils.getJson(userList);
    }

    @RequestMapping("/j3")
    @ResponseBody
    public String json3() throws JsonProcessingException {
        Date date = new Date();
        String str = JsonUtils.getJson(date);

        return str;
    }

json乱码解决

1.方法级

//produces：指定响应体返回类型和编码
@RequestMapping(value = "/j1",produces = "application/json;charset = utf-8")

2.配置级：应用于全部

springmvc配置文件里加上

<!--JSON乱码问题配置-->
    <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>
    </mvc:annotation-driven>

（二）FastJson

可以方便实现JSON对象与JavaBean对象的相互转换，实现JavaBean对象与JSON字符串的相互转换，实现JSON对象与JSON字符串的相互转换。

导入依赖

<dependency>
	<groupId>com.alibaba</groupId>
	<artifactId>fastjson</artifactId>
	<version>1.2.75</version>
</dependency>

方法

	@RequestMapping("/j4")
    @ResponseBody
    public String json4() throws JsonProcessingException {
        List<User> userList = new ArrayList<User>();
        User user1 = new User("zkk 1号", 14, "女");
        User user2 = new User("zkk 2号", 14, "女");
        User user3 = new User("zkk 3号", 14, "女");
        User user4 = new User("zkk 4号", 14, "女");
        userList.add(user1);
        userList.add(user2);
        userList.add(user3);
        userList.add(user4);


        System.out.println("=========Java对象转JSON字符串=========");

        String str1 = JSON.toJSONString(userList);
        System.out.println("JSON.toJSONString(userList) ==> " + str1);

        String str2 = JSON.toJSONString(user1);
        System.out.println("JSON.toJSONString(user1) ==> " + str2);


        System.out.println("=========JSON字符串转Java对象=========");
        User userConvert = JSON.parseObject(str2, User.class);
        System.out.println("JSON.parseObject(str2, User.class) ==> " + userConvert);


        System.out.println("=========Java对象转JSON对象=========");
        JSONObject jsonObject = (JSONObject) JSON.toJSON(user1);
        System.out.println(" (JSONObject) JSON.toJSON(user1) ==> " + jsonObject);


        System.out.println("=========JSON对象转Java对象=========");
        User userConvert2 = JSON.toJavaObject(jsonObject, User.class);
        System.out.println("JSON.toJavaObject(jsonObject, User.class) ==> " + userConvert2);

        return "Hello";
    }

打印结果

=========Java对象转JSON字符串=========
JSON.toJSONString(userList) ==> [{"age":14,"name":"zkk 1号","sex":"女"},{"age":14,"name":"zkk 2号","sex":"女"},{"age":14,"name":"zkk 3号","sex":"女"},{"age":14,"name":"zkk 4号","sex":"女"}]

JSON.toJSONString(user1) ==> {"age":14,"name":"zkk 1号","sex":"女"}

=========JSON字符串转Java对象=========
JSON.parseObject(str2, User.class) ==> User(name=zkk 1号, age=14, sex=女)

=========Java对象转JSON对象=========
 (JSONObject) JSON.toJSON(user1) ==> {"sex":"女","name":"zkk 1号","age":14}
 
=========JSON对象转Java对象=========
JSON.toJavaObject(jsonObject, User.class) ==> User(name=zkk 1号, age=14, sex=女)

posted @ 2021-02-12 16:43 musecho 阅读(76) 评论(0) 收藏举报

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【SpringMVC】(七)JSON

JSON

1.JSON和JavaScript对象互转

2.Controller 返回JSON数据

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