it is fine if my java code didn't complied into a package.
But if I complied my java code as a package, and call its native method outside. It give me "UnsatisfiedLinkError". And can not find my method. It is indeed the method is inside.
Thank a lot any helps. Email me on d.zhu@uea.ac.uk
What do you mean by compiling "into a package"? Your native method should be available as shared library so*.lib on Unix-derivates or *.dll on Wins. Make sure you use the correct method signatures as provided by javah and make the library available when you run your app.
Check out:
http://java.sun.com/docs/books/tutorial/native1.1/stepbystep/_library.html
I have found that javah does not generate the correct JNI function names when the native function is in a class that is within a Java package. The net result is an Unsatisfied link error.
The JNI function name must be included in the package name. The naming is a bit complicated and that's why javah should be used, except in this case it does not work. I can't quite remember exactly how it works, something like adding in _package_name_1 into the JNI name. The SWIG tool (http://www.swig.org) does generate the correct names when using packages. It is a tool which takes C or C++ header files and generates the JNI and Java classes for you so that you can call C/C++ code from Java. Once you have installed SWIG and run 'make check', have a look in the directory Examples/test-suite/java for the JNI naming for packages. I'll try remember to post the exact naming if you don't want to install SWIG.
If I run this through javah ( version 1.3.1):
// file test.java
package const_const;
public class test {
public final static native void foo(long jarg0);
}
it produces this header file test.h:
...
JNIEXPORT void JNICALL Java_test_foo (JNIEnv *, jclass, jlong);
...
It should be:
JNIEXPORT void JNICALL Java_const_1const_test_foo(JNIEnv *, jclass, jlong);
I get this to link and run.
I ran javah in the package directory, ie in directory test. I've just tried running it from the directory above it and get
// In file const_0005fconst_0005ctest.h:
JNIEXPORT void JNICALL Java_const_1const_0005ctest_foo (JNIEnv *, jclass, jlong);
This doesn't look right to me, I'm not sure if this will link or not.
Thanks a lot for everyone's helps and care of my question.
I have solved the problem. The main
problem for it that "javah" can not generate a correct header file for
java package. Therefore, i have to manually modify it and insert the package path for the header file.
For exampel, for the normal header declare like that
******************************************************
JNIEXPORT jbyteArray JNICALL
Java_CLASSNAME_functionname(JNIEnv *env, jobject obj)
******************************************************
but for the package header declare like that
*****************************************************
JNIEXPORT jbyteArray JNICALL
Java_PackagePath_CLASSNAME_functionname(JNIEnv *env, jobject obj)
*****************************************************************
We have to do some change for the header file.
Thank a again for everone's kindly helps.
