WebObjects 4.x: "_NSAutoreleaseNoPool ... just leaking" Messages

Symptom

When you spawn new Java worker threads in your WebObjects application, your console starts listing hundreds or thousands of messages like the following:

"Sep 18 08:08:16 MYWOApp[22010] *** _NSAutoreleaseNoPool(): Object 0x2a1e68
of class NSUnicodeString autoreleased with no pool in place - just leaking"

Solution

These messages are innocuous and should not affect your application, but they can be annoying because they can clutter a log file.

These messages appear because your Java code, in combination with the Java Bridge, is creating Objective-C objects. Objective-C uses "autorelease pools" for memory management. An autorelease pool gets created at the beginning of a request-response cycle for the main thread of a WebObjects application. If you spawn an additional thread in Java, you need to create an autorelease pool to manage the memory for the Objective-C objects that get created.

Insert the NSAutoreleasePool at the beginning of your Java thread's run() method:

int pool = NSAutoreleasePool.push();

- and release it at the end of the thread -

NSAutoreleasePool.pop(pool);

You'll need to do this for each thread you spawn because threads cannot share an NSAutoreleasePool.

Objective-C syntax

Note: This is the Objective-C equivalent of the Java push() and pop() methods above

myThreadFunc()
{
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  ... // do your stuff


  [pool release];
}