一.简介
JSON（JavaScript Object Notation, JS对象简谱）是一种轻量级的数据交换格式。它基于ECMAScript（European Computer Manufacturers Association, 欧洲计算机协会的一个子集，采用完全独立于编程语言的文本格式来存储和表示数据。简洁和清晰的层次结构使得 JSON 成为理想的数据交换语言。 易于人阅读和编写，同时也易于机器解析和生成，并有效地提升网络传输效率 简单来说,JSON 就是一种字符串格式,这种格式无论是在前端还是在后端,都可以很容易的转换成对象,所以常用于前后端数据传递
前端和后端的对象是不能直接传输的,所以都转为JSON字符串传输
1.前端需要将前端对象转化为JSON串,将JSON串转化为前端对象
2.后端需要将后端对象转化为JSON串,将JSON串转化为后端对象
二.前端对象和JSON的相互转换
1.JSON的语法
var obj="{'属性名':'属性值','属性名':{'属性名':'属性值'},'属性名':['值1','值1','值3']}"2. 对象和JSON的相互转换方法
通过JSON.parse()方法可以将一个JSON串转换成对象
通过JSON.stringify()方法可以将一个对象转换成一个JSON格式的字符串
3.示例代码
JSON转对象
/* 定义一个JSON串 */ var personStr ='{"name":"张小明","age":20,"girlFriend":{"name":"铁铃","age":23},"foods":["苹果","香蕉","橘子","葡萄"],"pets":[{"petName":"大黄","petType":"dog"},{"petName":"小花","petType":"cat"}]}' console.log(personStr) console.log(typeof personStr) /* 将一个JSON串转换为对象 */ var person =JSON.parse(personStr); console.log(person) console.log(typeof person) /* 获取对象属性值 */ console.log(person.name) console.log(person.age) console.log(person.girlFriend.name) console.log(person.foods[1]) console.log(person.pets[1].petName) console.log(person.pets[1].petType)
对象转JSON
/* 定义一个对象 */ var person={ 'name':'张小明', 'age':20, 'girlFriend':{ 'name':'铁铃', 'age':23 }, 'foods':['苹果','香蕉','橘子','葡萄'], 'pets':[ { 'petName':'大黄', 'petType':'dog' }, { 'petName':'小花', 'petType':'cat' } ] } /* 获取对象属性值 */ console.log(person.name) console.log(person.age) console.log(person.girlFriend.name) console.log(person.foods[1]) console.log(person.pets[1].petName) console.log(person.pets[1].petType) /* 将对象转换成JSON字符串 */ var personStr =JSON.stringify(person) console.log(personStr) console.log(typeof personStr)
三.后端对象和JSON的相互转换
1.导入jar包
在maven项目pom文件写入下面3个依赖
<dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-annotations</artifactId> <version>2.17.1</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-core</artifactId> <version>2.17.1</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.17.1</version> </dependency>
2.创建需要的传输数据对象
注意:要传输的类的定义一定要实现类的getter和setter方法不然就会报错.我们直接创建一个标准的javabean就可以了
例子
Dog类
public class Dog { private String name; private int age; public Dog() { } public Dog(String name, int age) { this.name = name; this.age = age; } /** * 获取 * @return name */ public String getName() { return name; } /** * 设置 * @param name */ public void setName(String name) { this.name = name; } /** * 获取 * @return age */ public int getAge() { return age; } /** * 设置 * @param age */ public void setAge(int age) { this.age = age; } public String toString() { return "Dog{name = " + name + ", age = " + age + "}"; } }Person类
public class Person { private String name; private int age; private Dog dog; public Person() { } public Person(String name, int age, Dog dog) { this.name = name; this.age = age; this.dog = dog; } /** * 获取 * @return name */ public String getName() { return name; } /** * 设置 * @param name */ public void setName(String name) { this.name = name; } /** * 获取 * @return age */ public int getAge() { return age; } /** * 设置 * @param age */ public void setAge(int age) { this.age = age; } /** * 获取 * @return dog */ public Dog getDog() { return dog; } /** * 设置 * @param dog */ public void setDog(Dog dog) { this.dog = dog; } public String toString() { return "Person{name = " + name + ", age = " + age + ", dog = " + dog + "}"; } }
3.对象转JSON
public void Object2Json() throws JsonProcessingException {
Dog dog = new Dog("小七", 2);
Person person = new Person("张三", 18, dog);
ObjectMapper objectMapper = new ObjectMapper();
String jsonStr = objectMapper.writeValueAsString(person);
System.out.println(jsonStr);
//{"name":"张三","age":18,"dog":{"name":"小七","age":2}}
}4.JSON转对象
public void Json2Object() throws JsonProcessingException {
String jsonStr = "{\"name\":\"张三\",\"age\":18,\"dog\":{\"name\":\"小七\",\"age\":2}}";
ObjectMapper objectMapper = new ObjectMapper();
Person person = objectMapper.readValue(jsonStr, Person.class);
System.out.println(person);
//Person{name = 张三, age = 18, dog = Dog{name = 小七, age = 2}}
}5.map转JSON
public void map2Json() throws JsonProcessingException {
Map<String, Object> map = new HashMap<>();
map.put("name", "张三");
map.put("age", 18);
map.put("dog", new Dog("小七", 2));
map.put("小王",new Person("小王", 18, new Dog("小七", 2)));
String mapStr = new ObjectMapper().writeValueAsString(map);
System.out.println(mapStr);
//{"小王":{"name":"小王","age":18,"dog":{"name":"小七","age":2}},"name":"张三","dog":{"name":"小七","age":2},"age":18}
}6.list和array转JSON
public void listArray2Json() throws JsonProcessingException {
ArrayList<String> list = new ArrayList<>();
list.add("张三");
list.add("李四");
String listStr = new ObjectMapper().writeValueAsString(list);
System.out.println(listStr);//["张三","李四"]
Person[] person = new Person[2];
person[0] = new Person("张三", 18, new Dog("小七", 2));
person[1] = new Person("李四", 18, new Dog("小七", 2));
String arrayStr = new ObjectMapper().writeValueAsString(person);
System.out.println(arrayStr);
//[{"name":"张三","age":18,"dog":{"name":"小七","age":2}},{"name":"李四","age":18,"dog":{"name":"小七","age":2}}]
}