Question

我有一个学生的ArrayList，我想从这个数组创建一个json数组。我已经看过使用ArrayList完成的示例，但那些在我的情况下不起作用。

我的学生班有：

String name, lastname;
ArrayList<String> courses;

我尝试了什么：

    JSONObject jsonObject = new JSONObject();
    JSONArray jsonPlayerArray = new JSONArray(Arrays.asList(students));
    jsonObject.put("jsonPlayerArray",jsonPlayerArray);
    System.out.println("AARRRAAYY: " + jsonPlayerArray.toString());
    System.out.println("JSONOBJEEECCCTTT: " + jsonObject.toString());

结果：

AARRRAAYY: [[null,null,null,null]]
JSONOBJEEECCCTTT: {"jsonPlayerArray":[[null,null,null,null]]}

想法可能是循环我的数组并单独添加

使用测试示例更新

致电方法

Test test = new Test(); 
test.addData();

有功能的课程

public class Test {
    ArrayList<Student> students = new ArrayList<>();
    ArrayList<String> courseSet = new ArrayList<>();

    public void addData(){
        courseSet.add("Java");
        courseSet.add("CSS");
        courseSet.add("Math");
        courseSet.add("Physics");

        students.add(new Student("Jimmy","sad", courseSet));
        students.add(new Student("Kim","don", courseSet));
        students.add(new Student("Barack","Obama", courseSet));
        createJSON();
    }

    public void createJSON(){
        try {
            List<Student> playerList = students;

            JSONObject jsonplayerObject = new JSONObject();
            JSONArray jsonPlayerArray = new JSONArray(playerList);
            jsonplayerObject.put("jsonPlayerArray", jsonPlayerArray);
            System.out.println("AARRRAAYY: " + jsonplayerObject.toString());


            for (Student s : students) {
                JSONArray jsArray = new JSONArray(s.getCourses());
                JSONObject jsonObject = new JSONObject();
                jsonObject.put("name", s.getName());
                jsonObject.put("lastName", s.getLastname());
                jsonObject.put("courses", jsArray);
                System.out.println("Json for player class: " + jsonObject.toString());
            }


    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    }

}

学生班级：

public class Student {

    String name, lastname;
    ArrayList<String> courses;

    public Student(String name, String lastname, ArrayList<String> courses) {
        this.name = name;
        this.lastname = lastname;
        this.courses = courses;
    }

    public String getName() {
        return name;
    }

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

    public String getLastname() {
        return lastname;
    }

    public void setLastname(String lastname) {
        this.lastname = lastname;
    }

    public ArrayList<String> getCourses() {
        return courses;
    }

    public void setCourses(ArrayList<String> courses) {
        this.courses = courses;
    }
}

结果：

    AARRRAAYY: {"jsonPlayerArray":[null,null,null]}
Json for player class: {"name":"Jimmy","lastName":"sad","courses":["Java","CSS","Math","Physics"]}
Json for player class: {"name":"Kim","lastName":"don","courses":["Java","CSS","Math","Physics"]}
Json for player class: {"name":"Barack","lastName":"Obama","courses":["Java","CSS","Math","Physics"]}

Answer 1

 public JsonArray createJsonArrayStudentList(List<Student> list) {
        JsonArray jsonArray = Json.createArrayBuilder();
        for(Student student: list) {
            jsonArray.add(Json.createObjectBuilder()
                .add("firstname", student.getFirstName())
                .add("lastname", student.getLastName()));
        }
        jsonArray.build();
        return jsonArray;
    }

Answer 2

你应该尝试使用Gson 首先将其添加到您的依赖项中

String json = new Gson().toJson(courses);

并试试这个

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Java ArrayList <class>到JSONArray

2 个答案: