Tomcat中OpenCV的UnsatisfiedLinkError

First of all, I have a basic example of OpenCV running in a main method. However, if I use OpenCV in a Spring Web Controller, an error is thrown.

I am getting an UnsatisfiedLinkError when running the following code inside a Tomcat Server, within STS (Spring Tool Suite), and have boiled the problem down to the following code:

System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
CascadeClassifier cascadeClassifier = new CascadeClassifier();

The run configurations of both the server and the "main" application contain the VM Arguments pointing to the OpenCV DLLs:

-Djava.library.path="C:opencvuildjavax64;C:opencvuildx64vc10in"

For reference, I have also included the pertinent bits of the stacktrace below:

org.springframework.web.util.NestedServletException: Handler processing failed;
nested exception is
java.lang.UnsatisfiedLinkError: org.opencv.objdetect.CascadeClassifier.CascadeClassifier_0()J
...
Caused by: java.lang.UnsatisfiedLinkError:
org.opencv.objdetect.CascadeClassifier.CascadeClassifier_0()J
    at org.opencv.objdetect.CascadeClassifier.CascadeClassifier_0(Native Method)
    at org.opencv.objdetect.CascadeClassifier.<init>(CascadeClassifier.java:38)
    at com.immersion.test.controllers.SimpleController.createClassifier(SimpleController.java:19)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

Note: I have read in several StackOverflow threads that the main cause of the UnsatisfiedLinkError is the missing System.loadLibrary(Core.NATIVE_LIBRARY_NAME) call. This is clearly not the case here, since it is being called just above where the exception is thrown.

解决方案

It turns out that the default run configuration to start a Tomcat server within STS/Eclipse is essentially just a launcher for Tomcat. This means that any VM Args that are added to the Tomcat 'run configuration' will not be transferred to the actual Tomcat instance.

On looking in tcruntime-instance.bat within the Tomcat directory (this is what ends up creating the tomcat java instance), we can see that simply by adding our intended VM Args to the JAVA_OPTS environment variable, the dlls will be available to Tomcat.

TL;DR:

So.. Simply add the the locations of the OpenCV binaries to your JAVA_OPTS environment variable:

-Djava.library.path="C:opencvuildjavax64;C:opencvuildx64vc10in"

For more information on setting JAVA_OPTS for Tomcat, see this SO question.