从MongoDB检索值时将DBObject转换为Java对象 [英] Converting DBObject to Java Object while retrieve values from MongoDB

问题描述

在我的Java应用程序中，我将mongoDB中的值存储在ArrayList（Java对象集）中。
如何从DBObject检索数据

From my Java application, I have stored the values in mongoDB in ArrayList(set of Java objects). How can I retrieve the data from DBObject

我将数据存储在mongoDB中，如下所示：

I am storing the data in mongoDB like this:

{  "students" : [{"firstName" : "Jesse", "lastName" : "Varnell", "age" : "15", "gender" : "M" }, { "firstName" : "John", "lastName" : "Doe", "age" : "13", "gender" : "F"}] }

我正在为学生提供Java对象：

I am having the Java Object for the Student like:

public class Student {
    public String firstName;
    public String lastName;
    public String age;
    public String gender;  // M, F      
}

我正在从mongoDB中检索数据，如：

I am retrieving the data from mongoDB like:

BasicDBObject query = new BasicDBObject();
query.put("user", username); 
DBCursor cursor = theCollection.find(query); 
while (cursor.hasNext()) {
    DBObject theObj = cursor.next();
    //How to get the DBObject value to ArrayList of Java Object?
}

推荐答案

你可以这样做：

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

BasicDBObject query = new BasicDBObject();
query.put("user", username); 
DBCursor cursor = theCollection.find(query); 
while (cursor.hasNext()) {
    DBObject theObj = cursor.next();
    //How to get the DBObject value to ArrayList of Java Object?

    BasicDBList studentsList = (BasicDBList) theObj.get("students");
    for (int i = 0; i < studentsList.size(); i++) {
        BasicDBObject studentObj = (BasicDBObject) studentsList.get(i);
        String firstName = studentObj.getString("firstName");
        String lastName = studentObj.getString("lastName");
        String age = studentObj.getString("age");
        String gender = studentObj.getString("gender");

        Student student = new Student();
        student.setFirstName(firstName);
        student.setLastName(lastName);
        student.setAge(age);
        student.setGender(gender);

        students.add(student);
    }               
}

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