Setting java.library.path property in java code

Question

Hi,
i'd like to set java.library.path property in java code to load a dll-library. I know that a funtional way is to run JVM with parameter -Djava.library.path=c:\tmp, but I need it do it IN CODE.
I'v tried this:
System.setProperty("java.library.path", "c:\\tmp");
System.loadLibrary("libapr");The library 'libapr.dll' is situated really in 'c:\tmp' directory, but I get 'java.lang.UnsatisfiedLinkError: no libapr in java.library.path' exception.
It seems like the already running java program doesn't use actual java.library.path set in previous step.
Is there any possibility to set java.library.path property in java code?
Thanx
Brny

Answer 1

I think the following code should work:
// Reset the "sys_paths" field of the ClassLoader to null.
          Class clazz = ClassLoader.class;
          Field field = clazz.getDeclaredField("sys_paths");
          boolean accessible = field.isAccessible();
          if (!accessible)
               field.setAccessible(true);
          Object original = field.get(clazz);
          // Reset it to null so that whenever "System.loadLibrary" is called, it will be reconstructed with the changed value.
          field.set(clazz, null);
          try {
               // Change the value and load the library.
               System.setProperty("java.library.path", "c:\\tmp");
               System.loadLibrary("libapr");
          finally {
               //Revert back the changes.
               field.set(clazz, original);
               field.setAccessible(accessible);
The idea is to make the static field "sys_paths" null so that it would construct the paths from the changed value.