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'}