how to autoGenearte _id instead of mongoDB ObjectId()

Question

How to genearate "_id" : "01A63D2B-1724-456E-B2C0-3B3729951654" instead of "_id" : ObjectId("570602c46399e320c3022c6b")

My Student.class

@Entity("student")
public class Student {
@Id
private String Id;

private long studentId;
private String studentName;
private String qualification;

public Student(){

}

public Student(long studentId, String studentName, String qualification) {
    this.studentId = studentId;
    this.studentName = studentName;
    this.qualification = qualification;
}

public long getStudentId() {
    return studentId;
}

public void setStudentId(long studentId) {
    this.studentId = studentId;
}

public String getStudentName() {
    return studentName;
}

public void setStudentName(String studentName) {
    this.studentName = studentName;
}

public String getQualification() {
    return qualification;
}

public void setQualification(String qualification) {
    this.qualification = qualification;
}
}

Function to add JSON Data to MOngoDB :

public void importFromJsonToMongoDB(File file) throws FileNotFoundException{

        try{
        String strJson = FileUtils.readFileToString(file, StandardCharsets.UTF_8);
        JSONArray jsonArr = new JSONArray(strJson);

        for (int i = 0; i < jsonArr.length(); i++)
        {
            JSONObject jsonObj = jsonArr.getJSONObject(i);
            String str = jsonObj.toString();
            ObjectMapper mapper = new ObjectMapper();
            Student std = mapper.readValue(str, Student.class);
            sr.save(std);
        }
        }catch (Exception e) {
        e.printStackTrace();
        System.out.println("Error While parsing data");
    }

* How to Auto Generate id? rather than MongoDb generating it.

Answer 1

Replace the existing NO-arg Constructor with following one in Student.class

public Student(){

  super();
  id = UUID.randomUUID().toString();
}

• This will generate random id instead of MongoDB ObjectId

Answer 2

I think you need to add "_id" field while inserting the document in MongoDB. since you are not specifying any "_id" field it will automatically be generated by MongoDB. You can also use getNextSequence() method of mongodb to generate the id according to your preference.

Note: StudentID and _id are two different entities in the same document.

I hope these link will be useful for you: https://docs.mongodb.org/manual/tutorial/create-an-auto-incrementing-field/