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POJava: load a library that depends on other libs
 

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  1. POJava: load a library that depends on other libs
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    <p>I want to load my own native libraries in my java application. Those native libraries depend upon third-party libraries (which may or may not be present when my application is installed on the client computer).</p> <p>Inside my java application, I ask the user to specify the location of dependent libs. Once I have this information, I am using it to update the "LD_LIBRARY_PATH" environment variable using JNI code. The following is the code snippet that I am using to change the "LD_LIBRARY_PATH" environment variable.</p> <p>Java code</p> <pre> public static final int setEnv(String key, String value) { if (key == null) { throw new NullPointerException("key cannot be null"); } if (value == null) { throw new NullPointerException("value cannot be null"); } return nativeSetEnv(key, value); } public static final native int nativeSetEnv(String key, String value); </pre> <p>Jni code (C)</p> <pre> JNIEXPORT jint JNICALL Java_Test_nativeSetEnv(JNIEnv *env, jclass cls, jstring key, jstring value) { const char *nativeKey = NULL; const char *nativeValue = NULL; nativeKey = (*env)->GetStringUTFChars(env, key, NULL); nativeValue = (*env)->GetStringUTFChars(env, value, NULL); int result = setenv(nativeKey, nativeValue, 1); return (jint) result; } </pre> <p>I also have corresponding native methods to fetch the environment variable.</p> <p>I can successfully update the LD_LIBRARY_PATH (this assertion is based on the output of C routine <code>getenv()</code>.</p> <p>I am still not able to load my native library. The dependent third-party libraries are still not detected.</p> <p>Any help/pointers are appreciated. I am using Linux 64 bit.</p> <p>Edit:</p> <p>I wrote a SSCE (in C) to test if dynamic loader is working. Here is the SSCE</p> <pre> #include #include #include #include int main(int argc, const char* const argv[]) { const char* const dependentLibPath = "...:"; const char* const sharedLibrary = "..."; char *newLibPath = NULL; char *originalLibPath = NULL; int l1, l2, result; void* handle = NULL; originalLibPath = getenv("LD_LIBRARY_PATH"); fprintf(stdout,"\nOriginal library path =%s\n",originalLibPath); l1 = strlen(originalLibPath); l2 = strlen(dependentLibPath); newLibPath = (char *)malloc((l1+l2)*sizeof(char)); strcpy(newLibPath,dependentLibPath); strcat(newLibPath,originalLibPath); fprintf(stdout,"\nNew library path =%s\n",newLibPath); result = setenv("LD_LIBRARY_PATH", newLibPath, 1); if(result!=0) { fprintf(stderr,"\nEnvironment could not be updated\n"); exit(1); } newLibPath = getenv("LD_LIBRARY_PATH"); fprintf(stdout,"\nNew library path from the env =%s\n",newLibPath); handle = dlopen(sharedLibrary, RTLD_NOW); if(handle==NULL) { fprintf(stderr,"\nCould not load the shared library: %s\n",dlerror()); exit(1); } fprintf(stdout,"\n The shared library was successfully loaded.\n"); result = dlclose(handle); if(result!=0) { fprintf(stderr,"\nCould not unload the shared library: %s\n",dlerror()); exit(1); } return 0; } </pre> <p>The C code also does not work. Apparently, the dynamic loader is not rereading the LD_LIBRARY_PATH environment variable. I need to figure out how to force the dynamic loader to re-read the LD_LIBRARY_PATH environment variable.</p>
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    1. COI really don't see why it doesn't work, since I've done something which is really similar (under Windows) and it works like a charm. By the way, have you tried (just for debugging purposes) loading the libraries with System.load(...) putting them in a "default" lib directory, just to see if the libraries are broken (and not you nativeSetEnv code). However, good question (+1)
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    2. CO..and that's off topic but I think you should free up memory allocated by GetStringUTFChars
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    3. CO@Giacomo: It works if I set LD_LIBRARY_PATH when launching my application. I will free up the allocated memory. Thanks for pointing it out. :)
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