java学习之json篇——java-json、gson、fastjson、jackson的使用

java学习之json篇——java-json、gson、fastjson、jackson的使用 建立实体类 user

package com.jock168.entity;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

import java.time.LocalDate;

// 用于指定生成JSON串的属性顺序
@JsonPropertyOrder({"age", "user_name"})
public class User {
    // 重命名属性的注解
    @JsonProperty("user_name")
    private String name;
    @JsonProperty("age")
    private int age;
    // 指定日期格式的注解
    @JsonFormat(timezone = "GMT+8", pattern = "yyyy-MM-dd")
    private LocalDate birth;
    // 指定在JSON串中不生成此属性
    @JsonIgnore
    private String gender;

    public User() {
    }

    public User(String name, int age, LocalDate birth) {
        this.name = name;
        this.age = age;
        this.birth = birth;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    public LocalDate getBirth() {
        return birth;
    }

    public void setBirth(LocalDate birth) {
        this.birth = birth;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + ''' +
                ", age=" + age +
                ", birth=" + birth +
                '}';
    }
}

student

package com.open.entity;


public class Student {
    private int id;
    private String name;
    private int age;
    private String gender;

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", age=" + age +
                ", gender='" + gender + ''' +
                '}';
    }

    public Student() {
    }

    public Student(int id, String name, int age, String gender) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
    }

    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 int getAge() {
        return age;
    }

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

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }
}

使用java-json实现json格式转字符串和字符串转json

package com.open.test;

import com.open.entity.Student;
import org.json.JSONObject;
import org.junit.Test;


public class JsonTest {
    @Test
    public void testJsonToStudent() {
        // 1. 提供要转换的 JSON 字符串
        String json = "{"gender":"男","name":"张三","id":1,"age":20}";
        // 2. 创建 JSonObject 对象
        JSONObject object = new JSONObject(json);
        // 3. 调用 get(String key)
        Student student = new Student();
        student.setId(object.getInt("id"));
        student.setName(object.getString("name"));
        student.setAge(object.getInt("age"));
        student.setGender(object.getString("gender"));
        System.out.println(student);
    }

    @Test
    public void testStudentToJson() {
        // 把 Student 对象转换为 JSON 字符串
        Student student = new Student(1, "张三", 20, "男");

        // JSON-java 中的方法
        // 要想使用 JSON官网提供的解析JSON工具，必须先创建 JSONObject对象
        JSONObject object = new JSONObject(student);
        // 调用 JSonObject 对象的 toString() 方法就会生成JSON字符串了
        String json = object.toString();
        System.out.println(json);
    }
}

gson

package com.xianopen.test;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;
import com.xianopen.entity.Student;
import org.junit.Test;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class GsonTest {
    @Test
    public void testJsonToMap() {
        String json = "{"1":{"id":1,"name":"张三","age":20},"2":{"id":2,"name":"李四","age":21},"3":{"id":3,"name":"王五","age":22},"4":{"id":4,"name":"赵六","age":23}}";

        Gson gson = new Gson();
        Map map = gson.fromJson(json, new TypeToken>() {
        }.getType());
        System.out.println(map);
    }
    @Test
    public void testMapToJson() {
        Map stus = new HashMap<>();
        stus.put(1, new Student(1, "张三", 20));
        stus.put(2, new Student(2, "李四", 21));
        stus.put(3, new Student(3, "王五", 22));
        stus.put(4, new Student(4, "赵六", 23));

        String json = new Gson().toJson(stus);
        System.out.println(json);
    }

    @Test
    public void testJsonToList() {
        //List List