JSON数据处理

2022-02-17 01:31:09

JSON数据处理

1.json的数据格式

1.1 数组格式

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
      /*
      * 定义json的格式数组格式
      * 中括号包裹，数组的元素的数据类型没有限制
      * 元素之间，逗号分开
      * */

      var jsonArray = ["k1","k2",100,9.9,true];
      //访问数据元素，通过索引访问
      console.log(jsonArray[1]);
      //遍历数组，取出数组中的元素
      for(var i=0;i<jsonArray.length; i++){
        console.log(jsonArray[i]);
      }

    </script>
</head>
<body>

</body>
</html>

1.2 对象格式

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
      /*
      * 定义json的对象格式
      * 大括号包裹，定义键值对，键必须是字符串类型，值得数据类型不限制
      * 键值对之间，是冒号分开
      * 每个键值对之间，逗号分开
      * */

      var jsonObject={
        "k1":"v1",
        "k2":"v2",
        "k3":100,
        "k4":9.9,
        "k5":true
      }
      //取出键值对，键找值的方式
      console.log(jsonObject.k1);
      console.log(jsonObject.k2);
      console.log(jsonObject.k3);
      console.log(jsonObject.k4);
      console.log(jsonObject.k5);

    </script>
</head>
<body>

</body>
</html>

1.3 数据嵌套对象

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>json数据的嵌套</title>
  <script type="text/javascript">
    /*
    * json数据的元素是对象
    * */

    var jsonArray = [
      {"name":"张三","age":20},
      {"name":"李四","age":22}
    ]

    //取出需要的数据 ，李四 22
    console.log( jsonArray[1].name+"----"+jsonArray[1].age);
    //遍历数据，取出数组中的元素
    for (var i = 0; i < jsonArray.length; i++) {
      console.log(jsonArray[i].name +"----"+jsonArray[i].age);
    }

  </script>
</head>
<body>

</body>
</html>

1.4 对象嵌套数据

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
        /*
        * json数据是对象，对象值是数组
        * */

        var jsonObject = {
            "k1": ["北京","上海","广州","深圳"],
            "k2": ["中国","美国","英国","法国"]
        }
        //取出上海
        console.log(jsonObject.k1[1]);
        //分别取出k1和k2键的数组，遍历
        for (var i = 0; i < jsonObject.k1.length; i++) {
            console.log(jsonObject.k1[i]);
        }
        console.log("============================================")
        for (var i = 0; i < jsonObject.k2.length; i++) {
            console.log(jsonObject.k2[i]);
        }
    </script>
</head>
<body>

</body>
</html>

1.5 json嵌套

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>json数据的嵌套</title>
    <script type="text/javascript">
      /*
      *  json的数据嵌套，你中有我，我中有你
      *  json的数据本质是对象
      *    对象是的键是字符串，对象的值是数组
      *    数组的元素是对象
      * */

      var json = {
        //键是k1，值是数组，数组的元素是对象
        "k1":[
          //数组的元素是两个对象
          {"name":"张三","age":20},
          {"name":"李四","age":21},
        ],
        "k2":[
          //数组的元素是两个对象
          {"name":"王五","age":23},
          {"name":"赵六","age":24},
        ],
      }

      //取出数据 李四 21
      console.log(json.k1[1].name+"---"+json.k1[1].age);

      //遍历k2键对应的数组
      for (var i = 0; i <json.k2.length ; i++) {
          console.log(json.k2[i].name+"---"+json.k2[i].age);
      }
    </script>
</head>
<body>

</body>
</html>

2.fastjson

它可以解析JSON格式的字符串，支持将Java Bean序列化为JSON字符串，也可以从JSON字符串反序列化到Java Bean。

@Data
public class Student {
    private Integer id;
    private String name;
    private Integer age;
    private String email;
    private Date birthday;
}

2.1 Java对象序列化到Json

//java中的对象，Student对象，序列化Json格式字符串
    @Test
    public void testObjectToJson(){
        Student student = new Student();
        student.setId(1);
        student.setName("张三");
        student.setAge(20);
        student.setEmail("zs@163.com");
        student.setBirthday(getDate());
        //student对象转成json格式的字符串
        //调用静态方法，传递要抓换的对象
        String jsonString = JSON.toJSONString(student);
        System.out.println(jsonString);
        //{"age":20,"birthday":1629451099346,"email":"zs@163.com","id":1,"name":"张三"}
    }

{
    "age":20,
    "birthday":1629451099346,
    "email":"zs@163.com",
    "id":1,
    "name":"张三"
}

//java中的集合List，序列化为Json格式字符串
    @Test
    public void testListToJson(){
        //集合List，存储Student对象
        ArrayList<Student> list = new ArrayList<>();
        Student student1 = new Student();
        student1.setId(1);
        student1.setName("张三");
        student1.setAge(20);
        student1.setEmail("zs@163.com");
        student1.setBirthday(getDate());

        Student student2 = new Student();
        student2.setId(2);
        student2.setName("赵四");
        student2.setAge(25);
        student2.setEmail("zs1@163.com");
        student2.setBirthday(getDate());
        //student对象存储到集合中
        list.add(student1);
        list.add(student2);
        //List集合，序列化为Json格式字符串
        String jsonString = JSON.toJSONString(list);
        System.out.println(jsonString);
        //转后的结果是数组，数组的元素是对象
        //[{"age":20,"birthday":1629451016542,"email":"zs@163.com","id":1,"name":"张三"},
        // {"age":25,"birthday":1629451016542,"email":"zs1@163.com","id":2,"name":"赵四"}]

    }

[
    {"age":20,"birthday":1629451016542,"email":"zs@163.com","id":1,"name":"张三"},
    {"age":25,"birthday":1629451016542,"email":"zs1@163.com","id":2,"name":"赵四"}
]

    //java中的集合Map,序列化为Json格式字符串
    @Test
    public void testMapToJson(){
        //创建map集合，键为字符串类型，值为Student对象
        HashMap<String, Student> map = new HashMap<>();

        Student student1 = new Student();
        student1.setId(1);
        student1.setName("张三");
        student1.setAge(20);
        student1.setEmail("zs@163.com");
        student1.setBirthday(getDate());

        Student student2 = new Student();
        student2.setId(2);
        student2.setName("赵四");
        student2.setAge(25);
        student2.setEmail("zs1@163.com");
        student2.setBirthday(getDate());
        //Map集合存储Student对象
        map.put("student1",student1);
        map.put("student2",student2);

        String jsonString = JSON.toJSONString(map);
        System.out.println(jsonString);
        //json格式字符串是对象，对象中有两个键，键对应的值是Student对象
        //{"student2":{"age":25,"birthday":1629451782886,"email":"zs1@163.com","id":2,"name":"赵四"},
        // "student1":{"age":20,"birthday":1629451782886,"email":"zs@163.com","id":1,"name":"张三"}}

    }

{
    "student2":{"age":25,"birthday":1629451782886,"email":"zs1@163.com","id":2,"name":"赵四"},
    "student1":{"age":20,"birthday":1629451782886,"email":"zs@163.com","id":1,"name":"张三"}
}

2.2 Json反序列化到java对象

 //Json格式字符串，反序列化到Java对象
    @Test
    public void testJsonToObject(){
        String jsonString = "{\"age\":20,\"birthday\":1629451099346,\"email\":\"zs@163.com\",\"id\":1,\"name\":\"张三\"}";
        //Json类的静态方法  parseObject
        //传递要反序列化的Json字符串，传递Java对象的class对象
        Student student=JSON.parseObject(jsonString,Student.class);
        System.out.println(student);
    }

 //Json格式字符串，反序列化到List集合
    @Test
    public void testJsonToList(){
        String jsonString = "[{\"age\":20,\"birthday\":1629451016542,\"email\":\"zs@163.com\",\"id\":1,\"name\":\"张三\"},\n" +
                " {\"age\":25,\"birthday\":1629451016542,\"email\":\"zs1@163.com\",\"id\":2,\"name\":\"赵四\"}]";
        //Json类的静态方法  parseArray
        //传递Json格式的字符串，传递转换后的集合的泛型的class对象
        List<Student> list = JSON.parseArray(jsonString, Student.class);
        list.forEach(System.out::println);
    }

//Json格式字符串，反序列化到Map集合
    @Test
     public void testJsonToMap(){
        String jsonString = "{\"student2\":{\"age\":25,\"birthday\":1629455067665,\"email\":\"zs1@163.com\",\"id\":2,\"name\":\"赵四\"}," +
                "\"student1\":{\"age\":20,\"birthday\":1629455067665,\"email\":\"zs@163.com\",\"id\":1,\"name\":\"张三\"}}";
        //json类的静态方法，parseObject
        //直接进行反序列化，Map集合是没有泛型的，泛型没有事不安全的
        //转后的集合，必须有泛型
        //调用parseObject，传递参数，TypeReference类型
        //将Map中所有的键存入到set集合中。因为set具备迭代器。所有可以迭代方式取出所有的键，再根据get方法。获取每一个键对应的值。
        //keySet():迭代后只能通过get()取key
        Map<String, Student> map = JSON.parseObject(jsonString, new TypeReference<Map<String, Student>>() {});
        for (String key : map.keySet()){
            System.out.println(key+":"+map.get(key));
        }
    }

JSON数据处理

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