Extract and load DLL from JAR

Question

My Java application uses a DLL library. How can I get it work from the JAR file?

The DLL is in the project's sources folder. I have to include it in my JAR, extract it at runtime (in the same directory of the jar) and load it.

Solution

You need to put dll in your library path (recommended ) before you try to load it. so that you will have to extract it from jar and copy it into lib path .

private void loadLib(String path, String name) {
  name = System.mapLibraryName(name); // extends name with .dll, .so or .dylib
  InputStream inputStream = null;
  OutputStream outputStream = null;
  try {
    inputStream = getClass().getResourceAsStream("/" + path + name);
    File fileOut = new File("your lib path");
    outputStream = new FileOutputStream(fileOut);
    IOUtils.copy(inputStream, outputStream);

    System.load(fileOut.toString());//loading goes here
  } catch (Exception e) {
    //handle
  } finally {
    if (inputStream != null) {
      try {
        inputStream.close();
      } catch (IOException e) {
        //log
      }
    }
    if (outputStream != null) {
      try {
        outputStream.close();
      } catch (IOException e) {
        //log
      }
    }
  }

}

Note: ACWrapper is the class holding the static method

Comments

[Oneiros]

Compiler can't find FileUtils and IOUtiles

[jmj]

you need to add commons-io jar in your classpath

[jmj]

System.getProperty("java.library.path"); //for win machine I remember its C:\\windows\\system32

[Oneiros]

I get Exception in thread "main" java.lang.UnsatisfiedLinkError: no j3dcore-ogl in java.library.path :(

[jmj]

it simply means that the dll hasn't been extracted to lib path.

[jmj]

Code works.. ! try to find out whats wrong. , 1. you are making mistake while passing arg. 2. you aren't copying in some proper place 3. code is working tested .

[Oneiros]

InputStream in = Frame3D.class.getResourceAsStream("/dll/j3dcore-ogl.dll"); File fileOut = new File(System.getProperty("java.library.path")); OutputStream out = FileUtils.openOutputStream(fileOut); Can't see what's wrong...

[jmj]

System.getProperty("java.library.path") it will return many path. just choose standard one and write your file there ,

[Oneiros]

ok now it works... but only if i run it form terminal! :( if i run the jar by double-clicking it, it freezes after loading the dll without throwing any exception... omg

[jmj]

Try from command line java -jar jarName.jar .. check if there is any excpetion . try running jar from command line from the same DIR where it is placed

[Oneiros]

yes, it works if i run with that command from the command line, without any exception... and it works also if i run it from netbeans :) i don't understand why... it's a simple HelloWorld using 3D libraries... thank you very much Jigar anyway! :D

[Oneiros]

solved ^^ stackoverflow.com/questions/4775487/…