Retrieve array values from mongodb with Java

Question

i have the following code :

DBCollection collsc = db.getCollection("StudentCourses") ;
BasicDBObject querysc = new BasicDBObject("StudentID",id ); 
DBCursor curssc = collsc.find(querysc);

while(curssc.hasNext()) {

    DBObject e = curssc.next();
    System.out.println("You are currently registered for the following modules: ") ; 
    System.out.println(e.get("CoursesRegistered")) ; 

}

This outputs:

You are currently registered for the following modules: 
[ "DigitalLogic" "OperatingSystems" , "FundamentalsCSE"]

However i want only the values to be returned from the array, i.e, DigitalLogic, OperatingSystems and FundamentalsCSE. I will use these values to populate a JList. Help please?

Zoon Nooz · Accepted Answer · 2012-03-11 10:51:36Z

17

Try to use

BasicDBList e = (BasicDBList) curssc.next().get("CoursesRegistered");

instead of

DBObject e = curssc.next();

and then get value from e.getIndex(index);

edited Mar 11, 2012 at 10:51

answered Mar 11, 2012 at 10:46

Zoon Nooz

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4 Comments

user1259962 Over a year ago

It doesn't work. I get exception as follows : Exception in thread "main" java.lang.ClassCastException: com.mongodb.BasicDBObject cannot be cast to com.mongodb.BasicDBList at modules.RegistrationSystem.main(RegistrationSystem.java:80)

user1259962 Over a year ago

Still exceptions. Exception in thread "main" java.lang.IllegalArgumentException: BasicBSONList can only work with numeric keys, not: [CoursesRegistered] at org.bson.types.BasicBSONList._getInt(BasicBSONList.java:161) at org.bson.types.BasicBSONList._getInt(BasicBSONList.java:152) at org.bson.types.BasicBSONList.get(BasicBSONList.java:104) at modules.RegistrationSystem.main(RegistrationSystem.java:82)

user1259962 Over a year ago

This did it. DBCollection collsc = db.getCollection("StudentCourses") ; BasicDBObject querysc = new BasicDBObject("StudentID",id ); DBCursor curssc = collsc.find(querysc); while(curssc.hasNext()) { //DBObject e = curssc.next(); BasicDBList e = (BasicDBList) curssc.next().get("CoursesRegistered"); System.out.println("You are currently registered for the following modules: ") ; for (int i=0;i<e.size();i++) { System.out.println(e.get(i)) ; } }

Shaik Mujahid Ali Over a year ago

How do i do this this with mongo-java 3.0 driver ?

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