dllfromjarclassloader.java

Very Nice library for using ActiveX controls directly from java without heavy knowledge of JNI, simp

package com.jacob.samples.JavaWebStart;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

/**
 * It is sometimes necessary to run Jacob without being able to install the dll
 * on the client machine. This is true in JavaWebStart (JWS) and possibly Applet
 * (assuming security allows access to the file system). The obvious thing to do
 * here is to jar up the Jacob.dll so that it can be downloaded the client along
 * with the rest of the resources. This is simple except that the System.Load()
 * function does not search jar files for DLLs. It searches the classpath. The
 * work around to this problem is to write the DLL to a temporary file and then
 * explicitly load the DLL calling passing the full path to the temporary file.
 * 
 * The following code demonstrates this idea.
 * 
 * @author joe
 * 
 */
public class DLLFromJARClassLoader {

	/**
	 * Load the DLL from the classpath rather than from the java path. This code
	 * uses this class's class loader to find the dell in one of the jar files
	 * in this class's class path. It then writes the file as a temp file and
	 * calls Load() on the temp file. The temporary file is marked to be deleted
	 * on exit so the dll is deleted from the system when the application exits.
	 * <p>
	 * Derived from ample code found in Sun's java forums <p.
	 * 
	 * @return true if the native library has loaded, false if there was a
	 *         problem.
	 */
	public boolean loadLibrary() {
		try {
			// Finds a stream to the dll. Change path/class if necessary
			InputStream inputStream = getClass().getResource("/jacob.dll")
					.openStream();
			// Change name if necessary
			File temporaryDll = File.createTempFile("jacob", ".dll");
			FileOutputStream outputStream = new FileOutputStream(temporaryDll);
			byte[] array = new byte[8192];
			for (int i = inputStream.read(array); i != -1; i = inputStream
					.read(array)) {
				outputStream.write(array, 0, i);
			}
			outputStream.close();
			temporaryDll.deleteOnExit();
			System.load(temporaryDll.getPath());
			return true;
		} catch (Throwable e) {
			e.printStackTrace();
			return false;
		}
	}

}