JSON

什么是JSON？

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

通常用于：

与服务器交换数据
在接收服务器数据时一般是字符串
可以使用JSON.parse() 方法将字符串解析为 JavaScript 对象
向服务器发送数据一般是字符串
可以使用JSON.stringify()，把JavaScript对象转为字符串

语法规格

JS中，一切皆对象，任何支持的类型都可以通过JSON来表示。例如，字符串、数字、数组、对象等。其中数组和对象是比较特殊且常用的两种类型：

对象表示为键值对
花括号保存对象：{"name1":"xxx", "name2":"xxx", "name3":"xxx", }
数据由逗号分隔
方括号保存数组【"xx","xxx","xxxx"】

测试

导包

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.11.3</version>
        </dependency>

spingmvc.xml

<?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">

    <context:component-scan base-package="com.kk.controller"/>

    <!--1.开启注解驱动-->
    <mvc:annotation-driven>
        <!--解决json乱码问题-->
        <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>

    <!--2.静态资源过滤-->
    <mvc:resources location="/js/" mapping="/js/**"/>
    <mvc:resources location="/css/" mapping="/css/**"/>
    <mvc:resources location="/img/" mapping="/img/**"/>

    <!--3.视图解析器-->
    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/page/"/>
        <property name="suffix" value=".jsp"/>
    </bean>
    
</beans>

controller

package com.kk.controller;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.kk.pojo.User;
import com.kk.utils.JsonUtil;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import java.util.Date;

@Controller
public class TestJson {


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

        User user = new User(1, "柯神_", "男");
        return new ObjectMapper().writeValueAsString(user);
    }

    @RequestMapping("/json1")
    @ResponseBody
    public String json1() throws JsonProcessingException {

        User user = new User(1, "柯神_", "男");
        return JsonUtil.getJson(user);
    }



    @RequestMapping("/time1")
    @ResponseBody
    public String jsonT1() throws JsonProcessingException {
        return JsonUtil.getJson(new Date());
    }


    @RequestMapping("/time2")
    @ResponseBody
    public String jsonT2() throws JsonProcessingException {
        return JsonUtil.getJson(new Date(),"yyyy-MM-dd HH:mm:ss");
    }



}

pojo

package com.kk.pojo;

import java.io.Serializable;

public class User implements Serializable {
    int id;
    String name;
    String sex;

    public User(int id, String name, String sex) {
        this.id = id;
        this.name = name;
        this.sex = sex;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                '}';
    }
}

可以将json封装成一个工具类

package com.kk.utils;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

import java.text.SimpleDateFormat;

public class JsonUtil {


    public static String getJson(Object o){
        ObjectMapper mapper = new ObjectMapper();

        try {
            return mapper.writeValueAsString(o);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }



    public static String getJson(Object o, String dataForm){
        ObjectMapper mapper = new ObjectMapper();

        //关闭时间戳
        mapper.configure(SerializationFeature.WRITE_DATE_KEYS_AS_TIMESTAMPS,false);
        //自定义时间格式

        SimpleDateFormat sdf = new SimpleDateFormat(dataForm);
        mapper.setDateFormat(sdf);
        try {
            return mapper.writeValueAsString(o);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }
}

菜鸟教程: https://www.runoob.com/json/json-tutorial.html

JSON

什么是JSON？

语法规格

测试

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