Java反射和OOM错误

Question

I am getting an java.lang.OutOfMemoryError and it seems to happen in a point I do reflection:

obj.getClass().getMethod(methodName, (Class[]) null);

What does this indicate? Does anyone know?

Answer 1

The code is the same as

obj.getClass().getMethod(methodName)

What does this indicate?

It indicates you need to read the Error message carefully as this is highly unlikely to be the cause as it doesn't creates very little memory.

Does anyone know?

If it really is the point at which the error occurs, the real cause is likely to be somewhere else. To resolve this you need to memory profile your application, or take a heap dump on OOME or increase the maximum heap size (or all three)

Answer 2

The point at which an out of memory error is thrown is often nowhere near the part of the code that's using lots of memory. It's thrown when the garbage collector detects a memory problem, but this can be in another thread from that which is consuming all your memory.

If you've got no idea where the problem lies, your best bet is to run a profiler.

Answer 3

I think that you have not enought PermGen space allocated. You could try -XX:PermSize=128M -XX:MaxPermSize=256M as java command line parameters for your app.

Answer 4

java.lang.OutOfMemoryError is thrown when the Java Virtual Machine cannot allocate an object because it is out of memory, and no more memory could be made available by the garbage collector.

I think it is nothing to do with obj.getClass().getMethod(methodName, (Class[]) null);

Do check why your application/program is getting out of memory.