nu.pattern.OpenCV.SharedLoader.SharedLoader() diagnoses Exception by Message - Fails on OpenJ9 - SOLUTION

[markmaker]

Hi

As discussed here:
https://groups.google.com/d/msg/openpnp/p2xiolO3pf0/XeOrKAXfBQAJ
we cannot use OpenJDK+OpenJ9 for OpenPNP due to some class loader issue with OpenCV.

I found the reason.

nu.pattern.OpenCV.SharedLoader.SharedLoader() diagnoses the exception by looking at the message. The message is slightly different with OpenJ9, therefore the exception is not correctly recognized and therefore falsely propagated:

opencv/src/main/java/nu/pattern/OpenCV.java

Lines 190 to 201 in fed49ee

	private SharedLoader() {
	try {
	System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
	logger.log(Level.FINEST, "Loaded existing OpenCV library \"{0}\" from library path.", Core.NATIVE_LIBRARY_NAME);
	} catch (final UnsatisfiedLinkError ule) {
	/* Only update the library path and load if the original error indicates it's missing from the library path. */
	String errorFragment = String.format("no %s in java.library.path", Core.NATIVE_LIBRARY_NAME);
	if (ule == null || !ule.getMessage().contains(errorFragment)) {
	logger.log(Level.FINEST, String.format("Encountered unexpected loading error."), ule);
	throw ule;
	}

The OpenJ9 VM generates this message:
opencv_java342 (Not found in java.library.path)

Suggestion:

/* Only update the library path and load if the original error indicates it's missing from the library path. */
        String errorFragment = String.format("no %s in java.library.path", );
        if (ule == null || !(ule.getMessage().contains(Core.NATIVE_LIBRARY_NAME) 
              && ule.getMessage().contains("java.library.path"))) {
          logger.log(Level.FINEST, String.format("Encountered unexpected loading error."), ule);
          throw ule;
}

I don't know how to bypass maven dependencies locally therefore I made no PR.

_Mark

[markmaker]

Workaround (until this Issue is fixed):

1. Run OpenPNP with OpenJDK8+Hotspot.
2. While OpenPNP is still running, search the temporary directory for the OpenCV shared library (e.g. %TEMP%\opencv_openpnp*\nu\pattern\opencv\windows\x86_64\opencv_java342.dll on Windows)
3. Copy the file into one of your PATH directories (I used HOMEDIR/maven/bin)
4. Close OpenPNP.
5. Change the JRE to OpenJDK8+OpenJ9
6. Run OpenPNP again.
7. Enjoy the fast loading time. :-)

_Mark

[vonnieda]

Fixed in #54