Tags: io

The JACOB Project
JACOB stands for JAva COM Bridge. The JACOB project started in 1999 by Dan Adler. It allows java programs to make native calls to system. JACOB supports on window x86 and x64 based native call.

Well its very useful library, however there are very few support article available on internet. We'll first understand basic java program that uses JACOB library and interacts with windows program that allows COM bridge support.

What JACOB actually do?
JACOB creates ActiveXObject of program identified using Program ID, Version independent Program ID or CLSID (Class ID aka Globally Unique Identifier) Read more about How to find CLSID or Program ID of program?

First Program With JACOB

package javaQuery.jacob;

import com.jacob.activeX.ActiveXComponent;
import com.jacob.com.Dispatch;
import com.jacob.com.LibraryLoader;
import com.jacob.com.Variant;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

/**
 * @author vicky.thakor
 * @date 28th December, 2013
 * http://sourceforge.net/projects/jacob-project/
 * First Program to understand how to use JACOB library
 */
public class JACOBGettingStarted {

    public static void main(String[] args) {
        /**
         * `System.getProperty("os.arch")`
         * It'll tell us on which platform Java Program is executing. Based on that we'll load respective DLL file.
         * Placed under same folder of program file(.java/.class).
         */
        String libFile = System.getProperty("os.arch").equals("amd64") ? "jacob-1.17-x64.dll" : "jacob-1.17-x86.dll";
        try {
            /* Read DLL file*/
            InputStream inputStream = jacobExample.class.getResourceAsStream(libFile);
            /**
             *  Step 1: Create temporary file under <%user.home%>\AppData\Local\Temp\jacob.dll 
             *  Step 2: Write contents of `inputStream` to that temporary file.
             */
            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();
            /**
             * `System.setProperty(LibraryLoader.JACOB_DLL_PATH, temporaryDll.getAbsolutePath());`
             * Set System property same like setting java home path in system.
             * 
             * `LibraryLoader.loadJacobLibrary();`
             * Load JACOB library in current System.
             */
            System.setProperty(LibraryLoader.JACOB_DLL_PATH, temporaryDll.getAbsolutePath());
            LibraryLoader.loadJacobLibrary();

            /**
             * Create ActiveXComponent using CLSID. You can also use program id here.
             * Next line(commented line/compProgramID) shows you how you can create ActiveXComponent using ProgramID.
             */
            ActiveXComponent compCLSID = new ActiveXComponent("clsid:{00024500-0000-0000-C000-000000000046}");
            /*ActiveXComponent compProgramID = new ActiveXComponent("Excel.Application");*/

            System.out.println("The Library been loaded, and an activeX component been created");
            
            /**
             * This is function/method of Microsoft Excel to use it with COM bridge.
             * Excel methods and its use can be found on
             * http://msdn.microsoft.com/en-us/library/bb179167(v=office.12).aspx
             * 
             * Understand code:
             * 1. Make Excel visible
             * 2. Get workbook of excel object.
             * 3. Open 1test.xls1 file in excel
             */
            Dispatch.put(compCLSID, "Visible", new Variant(true));
            Dispatch workbook = compCLSID.getProperty("Workbooks").toDispatch();
            Dispatch.call(workbook, "Open", new Variant("D:\\test\\test.xls"));

            /* Temporary file will be removed after terminating-closing-ending the application-program */
            temporaryDll.deleteOnExit();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Other Resources
1. JACOB Library
2. Microsoft Excel methods for COM bridge interaction
- For other Programs you've to Google it.

What's Next?
I'm gonna help you to learn How you can create your own DLL file for your customized system request and An applet example with source code. Well you've to wait for my next article. Subscribe to catch updates.

Other Resources:
Jacob + Visual Studio. Your custom .DLL to use in Java.

Tags: io