Avoiding LD_LIBRARY_PATH and DYLD_LIBRARY_PATH with JNI
This material demonstrates how to use JNI to access a shared library that has, in turn, dependent shared libraries, without the need to set LD_LIBRARY_PATH on Linux and DYLD_LIBRARY_PATH on MacOSX.
The requirement is that the dependent libs reside in some known relative location to the JNI library that uses them. This example demonstrates the simplest case, in which they are sitting in the same directory.
If you create an 'ordinary' JNI shared objects (with gcc or g++ -shared), and it references some other shared library, then, at runtime, you will get an UnsatisfiedLinkError unless you include the location of the other libraries in LD_LIBRARY_PATH/DYLD_LIBRARY_PATH.
To avoid this annoying requirement, follow the instructions below.
For Linux, when linking the JNI library, add:
to the link command line. Note that the above is the appropriate syntax for a Makefile, where $$ maps to a single $. The overall goal of this is to see "$ORIGIN" in the output of readelf -d.
For Mac OSX, there is no corresponding simple option for the link command line. Instead, you have to run an additional command to patch the pathname. Here is an example:
install_name_tool -change libsl2.dynlib "@loader_path/libsl2.dynlib" libjni.jnilib
In the example, the jni library is 'libjni.jnilib", while the library it links to is "libsl2.dynlib".
The correct form of this command depends on the 'install name' of libsl2.dynlib. You can use otool -L on the JNI lib to see the string as it comes out of the linker. The '-change' option finds the string you specify and replaces it with the string you supply.