保持Hibernate会话通过注释失效？(Keeping Hibernate Session from Expiring via Annotations? — failed to lazily initialize a collection of role)

 当试图访问一个包/集合的返回对象的成员时，我有一个hibernate DAO抛出一个“无法懒惰地初始化一个角色集合”异常。 
 
 我理解抛出异常的问题的范围。 Hibernate返回我的对象​​，并且对于任何集合，返回代理对象。 在我的调用者中，当我去访问这些代理对象时， 因为hibernate会话已经过期 ，所以抛出了这个异常。 
 
 我想知道的是，如何避免会话使用注释过期？ 可能吗？ 
 
 例如，如果我的调用方法是： 
 
@RequestMapping("refresh.url")
public ModelAndView refresh(HttpServletRequest request, HttpServletResponse response, int id) throws Exception {
    TestObject myObj = testObjDao.get(id);
    // throws the exception
    myObj.getCollection();
 
 我将如何使用注释来防止此异常？ 我知道一个解决方案是通过一个以伪代码形式显示的回调来扩展hibernate会话： 
 
@RequestMapping("refresh.url")
public ModelAndView refresh(HttpServletRequest request, HttpServletResponse response, int id) throws Exception {
    session = get hibernate session...
    session.doInSession(new SessionCallback() {
        TestObject myObj = testObjDao.get(id);
        // no longer throws the exception
        myObj.getCollection();
    });
 
 但是这在我需要访问集合的所有函数中似乎都是重复的。 是不是有一种方法可以在那里简单地拍@Transactional注释并完成它？ 如下所示： 
 
@RequestMapping("refresh.url")
@Transactional  // this doesn't extend the session to this method?
public ModelAndView refresh(HttpServletRequest request, HttpServletResponse response, int id) throws Exception {
    TestObject myObj = testObjDao.get(id);
    // throws the exception
    myObj.getCollection();
 
 感谢您的帮助，向我解释这一点。 

I have a hibernate DAO that is throwing a "failed to lazily initialize a collection of role" Exception when trying to access a member of the returned object that is a bag/Collection. 
 
I understand the scope of the problem throwing the exception. Hibernate returns my object, and for any Collections, returns proxy objects. In my caller, when I go to access those proxy objects, because the hibernate session has expired, this exception is thrown.
 
What I want to know is, how can I keep the session from expiring using annotations? Is it possible?
 
For instance if my calling method is:
 
@RequestMapping("refresh.url")
public ModelAndView refresh(HttpServletRequest request, HttpServletResponse response, int id) throws Exception {
    TestObject myObj = testObjDao.get(id);
    // throws the exception
    myObj.getCollection();
 
How would I prevent this exception using annotations? I know one solution would be to extend the hibernate session via a callback which in pseudocode might look something like:
 
@RequestMapping("refresh.url")
public ModelAndView refresh(HttpServletRequest request, HttpServletResponse response, int id) throws Exception {
    session = get hibernate session...
    session.doInSession(new SessionCallback() {
        TestObject myObj = testObjDao.get(id);
        // no longer throws the exception
        myObj.getCollection();
    });
 
but this seems rather repetitive to have in all of my functions that need to access collections. isn't there a way to simply slap an @Transactional annotation on there and be done with it? as in:
 
@RequestMapping("refresh.url")
@Transactional  // this doesn't extend the session to this method?
public ModelAndView refresh(HttpServletRequest request, HttpServletResponse response, int id) throws Exception {
    TestObject myObj = testObjDao.get(id);
    // throws the exception
    myObj.getCollection();
 
thanks for your help in explaining this to me.

原文：https://stackoverflow.com/questions/6316124