什么是JSON数据？

{
       "id":1,
      "age":20,
     "name":"张三"
}

JSON使用的是阿里提供的fastjson，需要提前引入依赖

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.71</version>
        </dependency>

1.JSON.toJSONString：将对象转换为JSON字符串

2.JSON.parseObject：将JSON字符串转换为实体类对象

3.JSON.parseArray：将JSON字符数组转换为list
 

测试：

 Student.java

public class Student{
    private Integer id;
    private String name;
    private Integer age;
}

 TestJSON.java

        Student student = new Student(1, "张三", 20);
        System.out.println("1.原始对象student："+student);

        //1.JSON.toJSONString：将对象转换为JSON字符串
        String studentStr = JSON.toJSONString(student);
        System.out.println("2.转换为JSON字符串："+studentStr);

        //2.JSON.parseObject：将JSON字符串转换为JSON对象，需要指定转换的实体类型
        //注意：提示尽量保持实体类型的属性名和类型与JSON字符串中的一致
        Student studentObj = JSON.parseObject(studentStr, Student.class);
        System.out.println("3.转换为JSON对象："+studentObj);

        ArrayList<String> list = new ArrayList<>();
        list.add(JSON.toJSONString(new Student(2, "李四", 21)));
        list.add(JSON.toJSONString(new Student(3, "王五", 22)));
        list.add(JSON.toJSONString(new Student(4, "赵六", 23)));
        System.out.println("4.原始list:"+list);
        //此处由于测试没有JSON字符串，需要转一下，注意，数组里面放的是JSON字符串！！
        //1.转换为JSON字符串
        String listStr = list.toString();
        System.out.println("5.list转换为String："+listStr);
        //2.将JSON字符串转换为对象数组
        List<Student> listObj = JSON.parseArray(listStr, Student.class);
        System.out.println("6.String转换为list："+listObj);

 结果展示：

1.原始对象student：Student(id=1, name=张三, age=20)
2.转换为JSON字符串：{"age":20,"id":1,"name":"张三"}
3.转换为JSON对象：Student(id=1, name=张三, age=20)
4.原始list:[{"age":21,"id":2,"name":"李四"}, {"age":22,"id":3,"name":"王五"}, {"age":23,"id":4,"name":"赵六"}]
5.list转换为String：[{"age":21,"id":2,"name":"李四"}, {"age":22,"id":3,"name":"王五"}, {"age":23,"id":4,"name":"赵六"}]
6.String转换为list：[Student(id=2, name=李四, age=21), Student(id=3, name=王五, age=22), Student(id=4, name=赵六, age=23)]