Hello guys,
I am trying to create a simple to-do API service via App Engine. I have
Userdata objects that have a set of
Project data objects and these Project data objects have a set of Taskobjects.
The following code should give you some idea about their
implementation and relationships.
@PersistenceCapable(detachable = "true")
public class User implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Long id;
@Persistent(mappedBy = "user")
private List<Project> projects;
}
@PersistenceCapable(detachable = "true")
public class Project implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key id;
@Persistent
private User user;
@Persistent(mappedBy = "project")
private List<Task> tasks;
}
@PersistenceCapable(detachable = "true")
public class Task implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key id;
@Persistent
private Project project;
}
What I am doing with User data object is the following (EntityManager is
defined as it is shown on App Engine help pages):
EntityManager em = EMFService.get().createEntityManager();
try {
User dev = em.find(User.class, id);
em.remove(dev);
} finally {
em.close();
}
*What I want to do is to get Project and Task data objects by their id,
which is the long number that corresponds to the data object not the key
combination with its parent that refers to the object as well. Since these
objects are child of others, I could't figure out how to get them by their
id value.*
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