Java 语言 ArrayList 和 JSONArray 相互转换

本篇主要讲解 ArrayList 和 fastjson 中的 JSONArray相互转换的几种常用方式，以实体类 Student.java 举例说明。

---

Student 实体类

/**

 * @author Miracle Luna

 * @version 1.0

 * @date 2019/7/5 18:06

 */

public class Student {

    private String name;     // 姓名

    private Integer age;     // 年龄

    private String gender;   // 性别

    public Student(String name, Integer age, String gender) {

        this.name = name;

        this.age = age;

        this.gender = gender;

    }

    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;

    }

    public String getGender() {

        return gender;

    }

    public void setGender(String gender) {

        this.gender = gender;

    }

    @Override

    public String toString() {

        return "Student{" +

                "name='" + name + '\'' +

                ", age=" + age +

                ", gender='" + gender + '\'' +

                '}';

    }

}

---

ArrayList 转成 JSONArray

简单总结了 6 种 方法（推荐 第5、6种），代码如下：

import com.alibaba.fastjson.JSON;

import com.alibaba.fastjson.JSONArray;

import com.alibaba.fastjson.JSONObject;

import java.util.ArrayList;

/**

 * @author Miracle Luna

 * @version 1.0

 * @date 2019/7/5 17:43

 */

public class ArrayListToJSONArray {

    public static void main(String[] args) {

        ArrayList<Student> studentList = new ArrayList<Student>();

        JSONArray studentJsonArray = new JSONArray();

        Student John = new Student("John", 16,"boy");

        Student Lily = new Student("Lily", 17, "girl");

        Student Jack = new Student("Jack", 18, "boy");

        studentList.add(John);

        studentList.add(Lily);

        studentList.add(Jack);

        System.out.println("=============== studentList info ================");

        System.out.println(studentList.toString());

        // 方式 1

        studentJsonArray = JSON.parseArray(JSONObject.toJSONString(studentList));

        System.out.println("\n方式 1: " + studentJsonArray.toJSONString());

        // 方式 2

        studentJsonArray = JSON.parseArray(JSON.toJSONString(studentList));

        System.out.println("\n方式 2: " + studentJsonArray.toJSONString());

        // 方式 3

        studentJsonArray = JSONObject.parseArray(JSONObject.toJSONString(studentList));

        System.out.println("\n方式 3: " + studentJsonArray.toJSONString());

        // 方式 4

        studentJsonArray = JSONObject.parseArray(JSON.toJSONString(studentList));

        System.out.println("\n方式 4: " + studentJsonArray.toJSONString());

        // 方式 5

        studentJsonArray = JSONArray.parseArray(JSONObject.toJSONString(studentList));

        System.out.println("\n方式 5: " + studentJsonArray.toJSONString());

        // 方式 6

        studentJsonArray = JSONArray.parseArray(JSON.toJSONString(studentList));

        System.out.println("\n方式 6: " + studentJsonArray.toJSONString());

        System.out.println("\n============== Lambda 表达式 遍历 JSONArray ============");

        studentJsonArray.forEach(student -> System.out.println("student info: " + student));

    }

}

执行结果如下：

=============== studentList info ================

[Student{name='John', age=16, gender='boy'}, Student{name='Lily', age=17, gender='girl'}, Student{name='Jack', age=18, gender='boy'}]

方式 1: [{"gender":"boy","name":"John","age":16},{"gender":"girl","name":"Lily","age":17},{"gender":"boy","name":"Jack","age":18}]

方式 2: [{"gender":"boy","name":"John","age":16},{"gender":"girl","name":"Lily","age":17},{"gender":"boy","name":"Jack","age":18}]

方式 3: [{"gender":"boy","name":"John","age":16},{"gender":"girl","name":"Lily","age":17},{"gender":"boy","name":"Jack","age":18}]

方式 4: [{"gender":"boy","name":"John","age":16},{"gender":"girl","name":"Lily","age":17},{"gender":"boy","name":"Jack","age":18}]

方式 5: [{"gender":"boy","name":"John","age":16},{"gender":"girl","name":"Lily","age":17},{"gender":"boy","name":"Jack","age":18}]

方式 6: [{"gender":"boy","name":"John","age":16},{"gender":"girl","name":"Lily","age":17},{"gender":"boy","name":"Jack","age":18}]

============== Lambda 表达式 遍历 JSONArray ============

student info: {"gender":"boy","name":"John","age":16}

student info: {"gender":"girl","name":"Lily","age":17}

student info: {"gender":"boy","name":"Jack","age":18}

---

JSONArray 转成 ArrayList

简单总结了 7 种 方法（推荐前 4种），代码如下：

import com.alibaba.fastjson.JSON;

import com.alibaba.fastjson.JSONArray;

import com.alibaba.fastjson.JSONObject;

import java.util.*;

/**

 * @author Miracle Luna

 * @version 1.0

 * @date 2019/7/5 18:36

 */

public class JSONArrayToArrayList {

    public static void main(String[] args) {

        JSONArray studentJSONArray = new JSONArray();

        List<Student> studentList = new ArrayList<Student>();

        Map<String, Object> JohnMap = new HashMap<String, Object>();

        JohnMap.put("name", "John");

        JohnMap.put("age", 16);

        JohnMap.put("gender", "boy");

        JSONObject John = new JSONObject(JohnMap);

        Map<String, Object> LilyMap = new HashMap<String, Object>();

        LilyMap.put("name", "Lily");

        LilyMap.put("age", 17);

        LilyMap.put("gender", "girl");

        JSONObject Lily = new JSONObject(LilyMap);

        Map<String, Object> JackMap = new HashMap<String, Object>();

        JackMap.put("name", "Jack");

        JackMap.put("age", 18);

        JackMap.put("gender", "boy");

        JSONObject Jack = new JSONObject(JackMap);

        studentJSONArray.add(John);

        studentJSONArray.add(Lily);

        studentJSONArray.add(Jack);

        System.out.println("\n=============== studentJSONArray info ================");

        System.out.println(studentJSONArray);

        System.out.println("\n=============== JSONArray to ArrayList(方式 1) ================");

        studentList = studentJSONArray.toJavaList(Student.class);

        studentList.forEach(student -> System.out.println("stundet info: " + student));

        System.out.println("\n=============== JSONArray to ArrayList(方式 2) ================");

        studentList = JSON.parseArray(studentJSONArray.toJSONString(), Student.class);

        studentList.forEach(student -> System.out.println("stundet info: " + student));

        System.out.println("\n=============== JSONArray to ArrayList(方式 3) ================");

        studentList = JSONObject.parseArray(studentJSONArray.toJSONString(), Student.class);

        studentList.forEach(student -> System.out.println("stundet info: " + student));

        System.out.println("\n=============== JSONArray to ArrayList(方式 4) ================");

        studentList = JSONArray.parseArray(studentJSONArray.toJSONString(), Student.class);

        studentList.forEach(student -> System.out.println("stundet info: " + student));

        System.out.println("\n=============== JSONArray to ArrayList(方式 5) ================");

        final ArrayList<Student> tmpList = new ArrayList<Student>();

        studentJSONArray.forEach(studentJson -> {

            JSONObject jsonObject = (JSONObject)studentJson;

            Student student = new Student(jsonObject.getString("name"), jsonObject.getInteger("age"), jsonObject.getString("gender"));

            tmpList.add(student);

        });

        studentList = tmpList;

        studentList.forEach(student -> System.out.println("stundet info: " + student));

        System.out.println("\n=============== JSONArray to ArrayList(方式 6) ================");

        studentList.clear();

        for (Object object : studentJSONArray) {

            JSONObject jsonObject = (JSONObject)object;

            Student student = new Student(jsonObject.getString("name"), jsonObject.getInteger("age"), jsonObject.getString("gender"));

            studentList.add(student);

        }

        studentList.forEach(student -> System.out.println("stundet info: " + student));

        System.out.println("\n=============== JSONArray to ArrayList(方式 7) ================");

        studentList.clear();

        for (int i = 0; i < studentJSONArray.size(); i++) {

            JSONObject jsonObject = (JSONObject)studentJSONArray.get(i);

            Student student = new Student(jsonObject.getString("name"), jsonObject.getInteger("age"), jsonObject.getString("gender"));

            studentList.add(student);

        }

        studentList.forEach(student -> System.out.println("stundet info: " + student));

    }

}

执行结果如下：

=============== studentJSONArray info ================

[{"gender":"boy","name":"John","age":16},{"gender":"girl","name":"Lily","age":17},{"gender":"boy","name":"Jack","age":18}]

=============== JSONArray to ArrayList(方式 1) ================

stundet info: Student{name='John', age=16, gender='boy'}

stundet info: Student{name='Lily', age=17, gender='girl'}

stundet info: Student{name='Jack', age=18, gender='boy'}

=============== JSONArray to ArrayList(方式 2) ================

stundet info: Student{name='John', age=16, gender='boy'}

stundet info: Student{name='Lily', age=17, gender='girl'}

stundet info: Student{name='Jack', age=18, gender='boy'}

=============== JSONArray to ArrayList(方式 3) ================

stundet info: Student{name='John', age=16, gender='boy'}

stundet info: Student{name='Lily', age=17, gender='girl'}

stundet info: Student{name='Jack', age=18, gender='boy'}

=============== JSONArray to ArrayList(方式 4) ================

stundet info: Student{name='John', age=16, gender='boy'}

stundet info: Student{name='Lily', age=17, gender='girl'}

stundet info: Student{name='Jack', age=18, gender='boy'}

=============== JSONArray to ArrayList(方式 5) ================

stundet info: Student{name='John', age=16, gender='boy'}

stundet info: Student{name='Lily', age=17, gender='girl'}

stundet info: Student{name='Jack', age=18, gender='boy'}

=============== JSONArray to ArrayList(方式 6) ================

stundet info: Student{name='John', age=16, gender='boy'}

stundet info: Student{name='Lily', age=17, gender='girl'}

stundet info: Student{name='Jack', age=18, gender='boy'}

=============== JSONArray to ArrayList(方式 7) ================

stundet info: Student{name='John', age=16, gender='boy'}

stundet info: Student{name='Lily', age=17, gender='girl'}

stundet info: Student{name='Jack', age=18, gender='boy'}