了解JSON

JSON简介

JSON:JavaScript Object Notation（JavaScript对象表示法）轻量级的文本数据交换格式。

JSON语法规则：JSON对象是以键值对的形式保存{"键":"值"} 表示数组方式为[{JSON对象}，{JSON对象}]

例：对象 {"ename":"Jack","age":"25"}

数组 [{"ename":"Jack","age":"25"},{"ename":"Lucy","age":"24"}]

JSON与JavaScript交互

**将字符串转换为JSON对象 ** JSON.parse()

demo1.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>字符串转JSON</title>
    <script type="text/javascript">
        var str = "{"name":"张三"}";
        var json = JSON.parse(str);
        console.log(str);
        console.log(json);
        document.write("姓名:" + json.name);//姓名：张三
    </script>
</head>
<body>
</body>
</html>

将JSON对象转换为字符串 JSON.stringify()

demo2.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>JSON转字符串</title>
    <script type="text/javascript">
        var json1 = {"name" : "张三"};
        var str= JSON.stringify(json1);
       document.write(str);//{"name":"张三"}
    </script>
</head>
<body>

</body>
</html>

JSON与Java交互

FastJSON解析器

FastJSON jar包下载：https://repo1.maven.org/maven2/com/alibaba/fastjson/1.2.53/fastjson-1.2.53.jar

Student.java

package JSON;

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

    public Student() {
    }

    public Student(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

FastJSON序列化

把JavaBean对象转成JSON格式的字符串 JSON.toJSONString(Object)

JSONdemo1.java

package JSON;

import com.alibaba.fastjson.JSON;
public class JSONdemo1 {
    public static void main(String[] args) {
        Student stu = new Student();
        stu.setName("张三");
        stu.setAge(20);
        String s = JSON.toJSONString(stu);
        System.out.println(s);//{"age":20,"name":"张三"}
    }
}

FastJSON反序列化

把JSON格式的字符串转化为Java Bean对象 JSON.parseArray(list, Object.class)

JSONdemo2.java

package JSON;
import com.alibaba.fastjson.JSON;
import java.util.ArrayList;
import java.util.List;

public class JSONdemo2 {
    public static void main(String[] args) {
        List list=new ArrayList();
        list.add(new Student("张三",18));
        list.add(new Student("李四",19));
        String s = JSON.toJSONString(list);
        System.out.println(s);//[{"age":18,"name":"张三"},{"age":19,"name":"李四"}]
        List<Student> stu = JSON.parseArray(s, Student.class);
        for (Student student : stu) {
            System.out.println(student.getName()+":"+student.getAge());
        }//张三:18  李四:19
    }
}

FastJSON注解

@JSONField(serialize="true/false") 设置serialize值true或false来设置是否下列属性序列化

@JSONField(format="0,000.00") 格式化属性格式