as3 URLLoader缓存移动应用的建议(as3 URLLoader Cache suggestions for mobile app)

 使用orphanRemoval ： 
 
@OneToMany(mappedBy="classroom", cascade={CascadeType.ALL}, orphanRemoval=true)
 
 每当从持久集中删除条目时，它将被删除。 这意味着您需要使用持久集 。 即你不能更换套装，而应该做： 
 
classroom.getRoster().clear();
classroom.getRoster().addAll(newRoster);
 
 
 示例如何将持久集与用户所需的集同步： 
 
/**
 * Assemble ClassroomUser relations.
 * @param classroom Classroom entity. Must be attached persistent or transient. Never null.
 * @param userIds Collection of user identifiers. Can be empty. Never null.
 */
private void assembleClassroomUsers(Classroom classroom, Collection<Integer> userIds) {
    // Make sure relation set exists (might be null for transient instance)
    if (classroom.getUsers() == null) {
        classroom.setUsers(new HashSet<ClassroomUser>());
    }
    // Create working copy of the collection
    Collection<Integer> ids = new HashSet<Integer>(userIds);
    // Check existing relations and retain or remove them as required
    Iterator<ClassroomUser> it = classroom.getUsers().iterator();
    while (it.hasNext()) {
        Integer userId = it.next().getUser().getId();
        if (!ids.remove(userId)) {
            it.remove(); // This will be picked by the deleteOrphans=true
        }
    }
    // Create new relations from the remaining set of identifiers
    for (Integer userId : ids) {
        ClassroomUser classroomUser = new ClassroomUser();
        classroomUser.setClassroom(classroom);
        // User must not have ClassroomUser relations initialized, otherwise Hibernate 
        // will get conflicting instructions what to persist and what to drop => error.
        // It might be safer to use dummy transient instance...
        User dummyUser = new User();
        dummyUser.setId(userId);
        classroomUser.setUser(dummyUser);
        classroom.getUsers().add(classroomUser);
    }
}
 
 这种方法看起来有点复杂。 您可以使用自定义equals / hashCode和一些Set<E>操作方法（例如来自Guava）创建更简单（但可能不太多）的东西。 

Use orphanRemoval:
 
@OneToMany(mappedBy="classroom", cascade={CascadeType.ALL}, orphanRemoval=true)
 
Whenever an entry is removed from the persistent set, it will get deleted. And this means you need to work with the persistent set. I.e. you are not allowed to replace the set, instead you should do:
 
classroom.getRoster().clear();
classroom.getRoster().addAll(newRoster);
 
 
EXAMPLE how to synchronize persistent set with a user required set:
 
/**
 * Assemble ClassroomUser relations.
 * @param classroom Classroom entity. Must be attached persistent or transient. Never null.
 * @param userIds Collection of user identifiers. Can be empty. Never null.
 */
private void assembleClassroomUsers(Classroom classroom, Collection<Integer> userIds) {
    // Make sure relation set exists (might be null for transient instance)
    if (classroom.getUsers() == null) {
        classroom.setUsers(new HashSet<ClassroomUser>());
    }
    // Create working copy of the collection
    Collection<Integer> ids = new HashSet<Integer>(userIds);
    // Check existing relations and retain or remove them as required
    Iterator<ClassroomUser> it = classroom.getUsers().iterator();
    while (it.hasNext()) {
        Integer userId = it.next().getUser().getId();
        if (!ids.remove(userId)) {
            it.remove(); // This will be picked by the deleteOrphans=true
        }
    }
    // Create new relations from the remaining set of identifiers
    for (Integer userId : ids) {
        ClassroomUser classroomUser = new ClassroomUser();
        classroomUser.setClassroom(classroom);
        // User must not have ClassroomUser relations initialized, otherwise Hibernate 
        // will get conflicting instructions what to persist and what to drop => error.
        // It might be safer to use dummy transient instance...
        User dummyUser = new User();
        dummyUser.setId(userId);
        classroomUser.setUser(dummyUser);
        classroom.getUsers().add(classroomUser);
    }
}
 
This approach might seem a little bit complex. You might be able to create something simpler (but probably not too much) with custom equals/hashCode and some Set<E> manipulation methods (e.g. from Guava).