Example of using shared libraries on Linux

This example takes you through the process of using native shared libraries with a Java™ application on Linux® systems.

1. Create a sample application, Sample.java.

   public class Sample
   {
      public native void printFromNative( );
   
      public static void main( String[] args )
      {
         Sample sample = new Sample( );
         sample.printFromNative( );
      }
   
      static
      {
         try
         {
            System.loadLibrary( "Sample" );
         }
         catch ( Exception e )
         {
            System.out.println( "ERROR: Unable to load libSample.so");
            e.printStackTrace( );
         }
      }
   }

2. Compile Sample.java.

   javac Sample.java

3. Use javah to create a header file for the native code.

   javah Sample

4. Create a file called Sample.c.

   #include <stdio.h>
   #include "Sample.h"
   
   JNIEXPORT void JNICALL Java_Sample_printFromNative( JNIEnv * env, jobject obj )
   {
      printf( "Printing from native\n" );
   }

5. Compile Sample.c and then link and bind into a shared library that can be loaded and called dynamically from Java.

   gcc -I<java_home>/include -o libSample.so -shared Sample.c

6. Run the Sample class.

   LD_LIBRARY_PATH=. java Sample

   or

   java -Djava.library.path=. Sample

   The program will output:

   Printing from native