I'm worring about JDO in GAE (Google App Engine). (GWT 2.4 and GAE 1.6.3 SDK and JDO 2.3)
I have a class "Users" which should save a Collection of "User" in a List, but it doesn't work.
When i save my Users-Class, then it creates the "Users"-Object in the Datebase and it also creates the User-Object in the List users. But when i load the Users-Object from the Database, the List users is empty... Do i have to load the list by my self? I guess that JDO schould load the list directy, when i load the Users-Object.
I need your Help here! Thanks in previous!
Could it be a Problem that i create the Key in abstract class PersistentUser and PersistentUsers? Could the LinkedList be the Problem?
My Code:
@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
@Version(strategy=VersionStrategy.VERSION_NUMBER)
public class Users extends PersistentUsers implements Serializable{
/**
*
*/
private static final long serialVersionUID = -21666269538993247L;
/**
* Mapped from Operator X
*/
@Persistent
private String operatorId;
@Persistent(mappedBy="userlist")
@Element(dependent = "true")
private List<User> users;
/**
*
* List of Ids of Users
*
*/
@Persistent(serialized = "true")
@Element(dependent = "true")
private List<String> userIds;
/**
* @return the users
*/
public List<User> getUsers() {
return users;
}
/**
* @param users the users to set
*/
public void setUsers(List<User> users) {
this.users = users;
}
...
}
The User Class:
@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
@Version(strategy=VersionStrategy.VERSION_NUMBER)
public class User extends PersistentUser implements Serializable{
/**
*
*/
private static final long serialVersionUID = 6899284258473985914L;
@Persistent
private String emailAddress;
@Persistent
private UserRole role;
/**
*
* Mapped from Userlist X from Operator Y
*/
@Persistent
private Users userlist;
public User(String email, UserRole role){
this.emailAddress = email;
this.role = role;
}
public String getEmailAddress() {
return emailAddress;
}
public void setEmailAddress(String emailAddress) {
this.emailAddress = emailAddress;
}
public UserRole getRole() {
return role;
}
public void setRole(UserRole role) {
this.role = role;
}
/**
* @return the userlist
*/
public Users getUserlist() {
return userlist;
}
/**
* @param userlist the userlist to set
*/
public void setUserlist(Users userlist) {
this.userlist = userlist;
}
}
PersistentUser and PersistentUsers Class are the same content (but because of JDO-AppEngine Inheritance Problem two seperate classes:
@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
@Inheritance(strategy = InheritanceStrategy.SUBCLASS_TABLE)
@Version(strategy=VersionStrategy.VERSION_NUMBER)
public abstract class PersistentUsers implements IPersitentObject {
/**
* Id
*
* Autogenerated String id of the Database
*
*/
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
protected Key encodedKey;
@Persistent
protected String username;
@Override
public String getId() {
if(encodedKey == null) return null;
return KeyFactory.keyToString(encodedKey);
}
/*public void setId(String id) {
this.encodedKey = id;
}*/
/**
* Helper function - get Version from DB
*/
@Override
public Long getVersion(){
...
}
/**
* Helper function - will save this instance in DB
*/
public void persist(){
...
}
/**
* Helper function - will remove this instance from DB
*/
public void delete(){
...
}
@Override
public final boolean checkUsername() {
...
}
}
Create User Code: ... if(RequestFactoryServlet.getThreadLocalRequest().getUserPrincipal() != null){
//Create New User
String email = RequestFactoryServlet.getThreadLocalRequest().getUserPrincipal().getName();
User u = UserFactory.getUser(email, UserRole.ADMINISTRATOR);
//u.persist();
//Create New Userlist
Users users = UserFactory.getUsers();
//Get Uids (normally empty)
LinkedList<String> uids = (LinkedList<String>) users.getUserIds();
if(uids==null){
uids = new LinkedList<String>();
}
uids.add(u.getId());
//Get DB-Userlist of current User-List
LinkedList<User> userlist = (LinkedList<User>) users.getUsers();
if(userlist==null){
userlist = new LinkedList<User>();
}
userlist.add(u);
users.setUserIds(uids);
users.setUsers(userlist);
u.setUserlist(users);
//Persit Userlist and Persist User
users.persist();
this.userlistId = users.getId();
}
...
Persistence Code:
public static void persist(IPersitentObject o){
PersistenceManager pm = Pmf.get().getPersistenceManager();
try{
pm.makePersistent(o);
} catch (Exception e) {
e.printStackTrace();
}finally {
pm.close();
}
}
