I have a "Student" entity type which is persistent. It is of many-to-
many relationship with "Team" entity type. Moreover, its keys are
stored in "List<Key> submittedStudentsKeys;" in "EvaluationTeam"
entity type
In one word, if I want to delete a "Student" tuple, I not only need to
remove the target object, but also remove all the traces of this
object in objects of other types.
Key stuKey = KeyFactory.stringToKey(req.getParameter("stuKey"));
PersistenceManager pm = PMF.get().getPersistenceManager();
Student stu = pm.getObjectById(Student.class,stuKey);
String stuName = stu.getName();
List<Key> teamKeys = stu.getTeams();
try {
for (Key teamKey: teamKeys){
Team team = pm.getObjectById(Team.class, teamKey);
List<Key> teamEvalKeys = team.getEvaluationTeams();
for (Key teamEvalKey : teamEvalKeys){
EvaluationTeam et =
pm.getObjectById(EvaluationTeam.class,
teamEvalKey);
List<EvalDetail> edsToBeRemoved = new
ArrayList<EvalDetail>();
for (EvalDetail ed: et.getEvalDetails()){
if
(!ed.isSelfEval()&&ed.getTo().equals(stuName)) {
edsToBeRemoved.add(ed);
continue;
}
if (ed.getFrom().equals(stuName)){
edsToBeRemoved.add(ed);
continue;
}
}
pm.deletePersistentAll(edsToBeRemoved);//remove
all
evalDetails relevant to this student
et.getSubmittedStudents().remove(stuKey);//remove student key
from submitted students
}
team.getStudents().remove(stuKey);//remove student
from this
team
}
pm.deletePersistent(stu);//remove student object
} finally {
pm.close();
}
However, the above action only removes the Student object. The
List<Key> in "Team" does not remove the key of the target Student
object. Same for "et.getSubmittedStudents()"
My Question is:
If I store an entity with one attribute "List<Sth> sths", how do I
remove an item from list?
Retrieving the list from datastore and use "remove()" on the list does
not work.
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