blocks|key|1502310|text|https://www.hibernate.org/43.html|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1502311|基本上，您有几个选择。|1502312|-You可以使用“在视图中打开会话”模式，在这种模式中，您可以使用过滤器/拦截器/面向方面编程风格的逻辑在服务器端逻辑开始时打开会话，并在会话结束时关闭会话。|1502313|-You可以实现跨越多个请求-响应周期的会话。|1502314|简单的老式Servlet过滤器是最简单的。|1502315|entityMap|0|LINK|mutability|MUTABLE|url^0|0|X|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|X|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|Y|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|Z|8|@]|9|@]|C|$]]|$1|L|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|4]]]]

<a href="https://www.hibernate.org/43.html" rel="noreferrer">https://www.hibernate.org/43.html</a>

Basically, you have a few options. 

-You can use the "open session in view" pattern where you use a filter/interceptor/AOP - style logic to open a session when server side logic begins, and close it when it's through.

-You could implement conversations spanning several request-response cycles.

A plain old Servlet Filter is the easiest.

blocks|key|1502363|text|当您使已读取某些数据的会话保持打开状态时，将使该事务保持打开状态。长时间运行的事务并不是什么大问题(尽管这可能取决于您的数据库)真正导致问题的是锁持有了很长一段时间，但这些锁可能只有在您实际更改数据库中的数据时才会创建。同样，这取决于您的数据库。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1502364|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

When you leave a session open that has read some data, you will leave that transaction open. Long running transactions aren't that big of a problem (although that might depend on your database) what really causes problems are locks hold for a long time, but these might only get created once you actually change data in the database. Again this depends on your database.

blocks|key|1287576|text|现在，我还没有使用Spring，但我已经在几个不同的项目中使用了Hibernate。我在最近的项目中采用的方法源于Defensive+Session+Handling模式(与servlet筛选器结合使用)，我们对此很满意。你可以找到更多的设计模式here。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1287577|entityMap|0|LINK|mutability|MUTABLE|url|https://www.hibernate.org/238.html|1|https://www.hibernate.org/36.html^0|1L|Q|0|3F|4|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

Now, I haven't used Spring, but I have used Hibernate in several different projects. The approach I settled on for the most recent project grew out of the <a href="https://www.hibernate.org/238.html" rel="nofollow noreferrer">Defensive Session Handling</a> pattern (in conjunction with a servlet filter), and we are happy with it. You can find more design patterns <a href="https://www.hibernate.org/36.html" rel="nofollow noreferrer">here</a>.

blocks|key|1502437|text|正如其他人所说，您应该阅读“在视图中打开会话”模式，其基本思想是在处理http请求的整个持续时间内打开一个hibernate会话。有hibernate+specific和spring两种解决方案--我以前用过spring，它工作得很好。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1502438|在问题中，您提到您不希望长时间打开事务。对于大多数人来说，这不是问题，因为每个请求都会得到相对较快的处理。但是，如果在您的情况下确实不可能，则此模式将不适用于您。你能详细解释一下为什么你不想让交易保持开放吗？|1502439|entityMap|0|LINK|mutability|MUTABLE|url|https://www.hibernate.org/43.html|1|http://static.springsource.org/spring/docs/2.5.x/api/org/springframework/orm/hibernate3/support/OpenSessionInViewInterceptor.html^0|1U|I|0|2D|6|1|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]|$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

As others have said, you should read up on "open session in view" pattern, the basic idea of which is to have a hibernate session open for the full duration of processing http request. There are both <a href="https://www.hibernate.org/43.html" rel="nofollow noreferrer">hibernate specific</a> and <a href="http://static.springsource.org/spring/docs/2.5.x/api/org/springframework/orm/hibernate3/support/OpenSessionInViewInterceptor.html" rel="nofollow noreferrer">spring</a> solutions - I used spring's before and it works fine.

In the question you mention that you don't want to have transaction open for a long time. For most of the people this is not an issue because each request is processed relatively quickly. However if in your case it is indeed impossible this pattern will not work for you. Can you elaborate on why you don't want the transactions kept open?

blocks|key|1502498|text|最后一个选项似乎被忽略了，那就是你可以通过使用连接来基于你的用例来构建你的对象图。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1502499|这将导致对象被初始化，即不是代理。|1502500|如果您控制了客户端(即，您没有创建开放服务发布api)，则可以使用此方法，因为您需要知道当会话由于事务已关闭而关闭时所触及的状态。|1502501|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

One final option which seems to of been missed is you can build your object graph based on your use-case by using a JOIN.

This will result in the object being initialized, i.e the will not be a proxy. 

Use this approach if you are in control of the client (i.e you not creating open service publishing an api) because you need to know what state is being touched when the session is closed because the transaction has closed.

I currently mark collections in entity beans as eager to avoid getting a lazy initialization exception when I try to access the collection properties after loading the bean with the EntityManager.

If I instead leave the collection as lazy loading, how do I keep a session open? I thought about trying @Transactional, but even if that worked I wouldn't want to do it because it doesn't seem right to leave a transaction open over a long method.

In Spring with jpa/hibernate, how do I keep a session open to avoid lazy initialization exceptions?

数据库

服务器

目前，我将实体bean中的集合标记为急于避免在使用EntityManager加载bean后尝试访问集合属性时出现延迟初始化异常。如果我将集合保留为延迟加载，如何保持会话打开？我想过尝试@ transaction，但即使这样做有效，我也不想这么做，因为在一个长方法上打开一个事务似乎是不对的。

问在使用jpa/hibernate的Spring中，如何保持会话打开以避免延迟初始化异常？
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