Comments on: Advanced Hibernate: Proxy Pitfalls http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/ Software development done right! Wed, 08 Feb 2012 14:41:38 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Stephane http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-114887 Stephane Thu, 08 Dec 2011 15:45:55 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-114887 Nice article. Thanks for that. Just a little spelling mistake: thr proxy Nice article. Thanks for that. Just a little spelling mistake: thr proxy

]]> By: Stephane http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-113558 Stephane Sun, 20 Nov 2011 18:33:33 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-113558 Hello, I have a similar issue I guess, related to the proxy mechanism I suspect. It is described on the Hibernate forum. I wonder if any of you guys would see something interesting in it. https://forum.hibernate.org/viewtopic.php?f=1&t=1011804 Thanks ! Stephane Hello,

I have a similar issue I guess, related to the proxy mechanism I suspect.

It is described on the Hibernate forum.

I wonder if any of you guys would see something interesting in it.

https://forum.hibernate.org/viewtopic.php?f=1&t=1011804

Thanks !

Stephane

]]> By: Sean van Buggenum http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-96444 Sean van Buggenum Tue, 14 Sep 2010 02:25:22 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-96444 Hi all, I am just now revisiting hibernate, and came across this great, helpful blog. Thanks. However, I do have a question. I know this was written 2 years ago, but I hope someone can anyway clear this up for me. I would like to question "Proxy Pitfall 2: instanceOf". When one has a class A, and a class B extends A, one can correctly assert the following: A aObj = new A(); B bObj = new B(); assertTrue(aobj instanceof A && bObj instanceof A); This should pass, because while bObj is not an exact instance of class A, the operator 'instanceof' evaluates as true of an object is an instance of the specified class OR an instance of a subclass of the specified class. So, in other words, the 'instanceof' operator causes no problems in testing that an object (which is probably a proxy object) is an instance of the derived class, because it will be. So, given this is true, can I assume that the problem mentioned here is more a problem of testing exactly that an object is of a the exact class A (through testing class equals ) ? for example: bObj.getClass().equals(A.class) which will indeed fail. Hi all,

I am just now revisiting hibernate, and came across this great, helpful blog. Thanks.

However, I do have a question. I know this was written 2 years ago, but I hope someone can anyway clear this up for me.

I would like to question “Proxy Pitfall 2: instanceOf”.

When one has a class A,
and a class B extends A,

one can correctly assert the following:

A aObj = new A();
B bObj = new B();

assertTrue(aobj instanceof A && bObj instanceof A);

This should pass, because while bObj is not an exact instance of class A, the operator ‘instanceof’ evaluates as true of an object is an instance of the specified class OR an instance of a subclass of the specified class.

So, in other words, the ‘instanceof’ operator causes no problems in testing that an object (which is probably a proxy object) is an instance of the derived class, because it will be.

So, given this is true, can I assume that the problem mentioned here is more a problem of testing exactly that an object is of a the exact class A (through testing class equals ) ?

for example:

bObj.getClass().equals(A.class)

which will indeed fail.

]]> By: Laziness (in proxies) is a virtue | Redfin Developers’ Blog http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-93683 Laziness (in proxies) is a virtue | Redfin Developers’ Blog Tue, 29 Dec 2009 17:51:44 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-93683 [...] the lazy proxy is NOT the same as the actual object. If you depend on the datatype of the object, you may have problems, since the type of the proxy isn’t the same as the type of the actual object (e.g. a proxy [...] [...] the lazy proxy is NOT the same as the actual object. If you depend on the datatype of the object, you may have problems, since the type of the proxy isn’t the same as the type of the actual object (e.g. a proxy [...]

]]> By: donamir http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-92879 donamir Wed, 21 Oct 2009 10:12:24 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-92879 Useful article, tanks. Useful article, tanks.

]]> By: JPA implementation patterns: Lazy loading | Xebia Blog http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-91629 JPA implementation patterns: Lazy loading | Xebia Blog Mon, 27 Apr 2009 19:30:52 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-91629 [...] when invoking the identifier getter method. My colleague Maarten Winkels has blogged about the pitfalls of these Hibernate proxies last [...] [...] when invoking the identifier getter method. My colleague Maarten Winkels has blogged about the pitfalls of these Hibernate proxies last [...]

]]> By: Pravin http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-66335 Pravin Thu, 04 Dec 2008 10:51:49 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-66335 Hi I am having problem with same with proxy i want to check whether it is the instance of a class out of two classes as the object is of Base class Like: C is base class and A,B are derived so i want to check whether new C() instanceof A or B. Please help me Pravin Hi I am having problem with same with proxy i want to check whether it is the instance of a class out of two classes as the object is of Base class Like: C is base class and A,B are derived so i want to check whether new C() instanceof A or B.

Please help me

Pravin

]]> By: Frits Jalvingh http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-54474 Frits Jalvingh Thu, 25 Sep 2008 12:27:39 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-54474 @Christian: Bytecode-enhancing the actual class would be great but in runtime is hard to do because they need to be enhanced before they are ever used which is complex. A simpler alternative is to create a proxy for the actual object itself and *not* have the "target" kludge. Simply use the fields in the proxy directly. This still does not properly solve the inheritance scheme but that is impossible with lazy loading anyway. The simpler alternative has way less problems than the current implementation and *can* be built in an afternoon (my replacement for Hibernate called SPF has it, and it took that long ;-) Sadly, Hibernate sucks bigtime and is not a good persistence framework at all; it is just the one that sucks the least... @Christian:
Bytecode-enhancing the actual class would be great but in runtime is hard to do because they need to be enhanced before they are ever used which is complex.

A simpler alternative is to create a proxy for the actual object itself and *not* have the “target” kludge. Simply use the fields in the proxy directly. This still does not properly solve the inheritance scheme but that is impossible with lazy loading anyway.

The simpler alternative has way less problems than the current implementation and *can* be built in an afternoon (my replacement for Hibernate called SPF has it, and it took that long ;-)

Sadly, Hibernate sucks bigtime and is not a good persistence framework at all; it is just the one that sucks the least…

]]> By: Christian http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-45076 Christian Mon, 09 Jun 2008 09:47:45 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-45076 my < and > got lost, it should read: <sarcasm>Hey, its the world best ORM and everything else is crap</sarcasm> my < and > got lost, it should read:
<sarcasm>Hey, its the world best ORM and everything else is crap</sarcasm>

]]> By: Christian http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-45075 Christian Mon, 09 Jun 2008 09:46:47 +0000 http://blog.xebia.com/2008/03/08/advanced-hibernate-proxy-pitfalls/#comment-45075 my 2 cents: pitfall #2 is just a design/implementation bug, where Hibernate has never admitted, that it is a bug Hey, its the world best ORM and everything else is crap The JPA spec has addressed this: 2.1.7. ...Relationships are polymorphic. Nothing more to say, except that it sometimes does still occur in Hibernates JPA implementation (but now its a bug, not a feature) Regarding Proxies in general: The Hibernate approach is the we-can-implement-it-on-a-weekend approach. Whereas JDO has featured a smarter approach (available in many JPA implementations), i.e. use byte code enhancement to implement the proxy functionality in the class itself, which solves most of the problems. (But you can't design and implement that on a weekend.) Christian my 2 cents:
pitfall #2 is just a design/implementation bug, where Hibernate has never admitted, that it is a bug Hey, its the world best ORM and everything else is crap

The JPA spec has addressed this: 2.1.7. …Relationships are polymorphic.
Nothing more to say, except that it sometimes does still occur in Hibernates JPA implementation (but now its a bug, not a feature)

Regarding Proxies in general: The Hibernate approach is the we-can-implement-it-on-a-weekend approach. Whereas JDO has featured a smarter approach (available in many JPA implementations), i.e. use byte code enhancement to implement the proxy functionality in the class itself, which solves most of the problems. (But you can’t design and implement that on a weekend.)

Christian

]]>