@Entity

public class User {

@Id
@Column(name = "USER_ID", allowsNull="false")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key userId;

@Column(name = "USER_NAME", allowsNull="false")
private String userName;

@OneToOne(cascade = CascadeType.ALL,optional=false,orphanRemoval = true)
@JoinColumn(name = "USER_ID")
private UserDetails userDetails;
//getters & setters

}



@Entity(name="USER_DETAILS")

public class UserDetails {

@Id
@Column(name = "USER_ID", allowsNull="false")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key userId;

@Column(name = "USER_FULLNAME", allowsNull="false")
private String userFullname;

@Column(name = "USER_IMAGEURL", allowsNull="false")
private String userImageURL;

@Column(name = "USER_PASSPHRASE", allowsNull="false")
private String userPassPhrase;

@OneToOne(cascade = CascadeType.ALL,optional=false)
@JoinColumn(name = "USER_ID")
private UserPassword userPassword;
//getters & setters
}


@Entity(name = "USER_PASSWORD")

public class UserPassword {

@Id
@Column(name = "USER_ID", allowsNull="false")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key userId;

@Column(name = "USER_PASSWORD", allowsNull="false")
private String userPassword;
//getters & setters
}

public void removeAllUsers() {

    log.info("UserEndpoint.removeAllUsers().....");
    EntityManager mgr = getEntityManager();
    User user = new User();
    try {
        CollectionResponse<User> allUsers = listUser(null, null);
        Collection<User> users = allUsers.getItems();
        Iterator<User> itr = users.iterator();

 log.info("UserEndpoint.removeAllUsers()....itr.hasNext="+itr.hasNext());
        while(itr.hasNext()){
            user = itr.next();
            user = mgr.find(User.class, user.getUserId());
            //mgr.getTransaction().begin();
            mgr.remove(user);
            //mgr.getTransaction().commit();

            log.info("UserEndpoint.removeAllUsers()....User removed");
        }

    } finally {
        mgr.close();
    }
    log.info("UserEndpoint.removeAllUsers()....End");
}

WARNING: Delete of com.bean.User@15a9289 needs delete of related object at com..bean.User.userDetails but cannot delete it direct since FK is here
Jun 12, 2014 12:04:01 PM com.google.api.server.spi.SystemService invokeServiceMethod
INFO: cause={0}
javax.persistence.PersistenceException: Illegal argument
at org.datanucleus.api.jpa.NucleusJPAHelper.getJPAExceptionForNucleusException(NucleusJPAHelper.java:298)
at org.datanucleus.api.jpa.JPAEntityManager.close(JPAEntityManager.java:197)`enter code here`
at com.cloudmobilebanking.bean.UserEndpoint.removeAllUsers(UserEndpoint.java:202)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

Caused by: java.lang.IllegalArgumentException: cross-group transaction need to be explicitly specified, see TransactionOptions.Builder.withXGfound both Element {
 type: "User"
 id: 0x10780000000000
 }
 and Element {
 type: "User"
 id: 0x12b80000000000
}

public void deletAllUsers(){
    log.info("UserEndpoint.deletAllUsers...");
    List<User> users =  ofy().load().type(User.class).list();
    User user = null;
    try{
        for(int i=0; i< users.size(); i++){
            user = users.get(i);
            UserDetails userDetails = user.getUserDetails();
            UserPassword userPassword = user.getUserPassword();
            ofy().delete().entity(userDetails).now();
            ofy().delete().entity(userPassword).now();
            ofy().delete().entity(user).now();
        }
    }

    catch(Exception e){
        log.info("AccountEndpoint.deleteAllUsers()...exception="+e.getMessage());
    }
    log.info("AccountEndpoint.deletAllUsers...all users deleted");
}