Nick Johnson

I'm reminded tonight of why I hate things that happen by "magic" in code. They are great when they're working correctly, but an impossible pain in the ass to debug when things go wrong. This is the primary reason why I dislike AOP; how do you debug something that isn't in your code? Toplink's "weaving" is very AOP-ish; it's effectively intercepting Java bytecode for setting the values for fields.

Or rather, it's not doing it very effectively, if I may overload usage of the word, because it's totally broken in a very simple and stupid way which even a primitive test case should reveal. It fails to correctly instrument put field operation for a field that has an associated Entity. In this case, that means that when I try to set my MessageRoot on my Message, I get this:

java.lang.NoSuchMethodError:
net.spatula.tally_ho.model.Message._toplink_setroot(Lnet/spatula/tally_ho/model/MessageRoot;)V
 at net.spatula.tally_ho.model.Message.setRoot(Message.java:169)

As you can probably imagine, I did not write a method called _toplink_setroot. The problem is, neither did Toplink, even though it should have.

Since the Toplink instrumentation code doesn't appear to do any logging of any kind, it is utterly impossible to debug this problem. I have exactly nothing at all to go on, other than the name of a method that doesn't exist, which Toplink should have supplied if it wanted to call it.

Much as I wanted to use Toplink for this project, this problem is a complete deal-breaker. What's particularly startling to me is that such a simple test case can fail without anyone noticing.

Next I guess I'll try BEA's Open JPA (Kodo) and see if they can manage to do proper lazy loading of a 1:1 relationship AND let me create that relationship too... since that's too much to ask of Toplink.

Labels: AOP, kodo, NoSuchMethodError, open JPA, software, toplink, weaving