Java中ArrayList和JSONArray相互转换的方法

ゞ浴缸里的玫瑰 2023-02-26 13:23 28阅读 0赞

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**

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;
    
    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.*;
    
    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'}