It's me It's me - 3 months ago 18
Java Question

Converting DBObject to Java Object while retrieve values from MongoDB

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

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"}] }


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
}


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?
}

Answer

You can do it as follows :

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);
    }               
}