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Thread: Using DLL in Java

  1. #1
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    Question Using DLL in Java

    I have a working sample program on how to use DLL in java with JNI. I use to be properly implemented:
    /* Test.java */
    public class Test {
        /*Load the dll that exports functions callable from java*/
        static {System.loadLibrary("TestImp");} /* Name Of DLL : TestImp.dll */
        /*Imported function declarations*/
    	public native void print(String msg);
    	public native byte[] readFile(String path);
    	public native int searchFile(String path, byte[] b, int bLength);
    	public native String[] findFiles(String path, String mask);
    	public native String[] checkProcess(String processName, boolean killIt, boolean printOutput);
    	public native int startProcess(String commandLine, String workingDir);
    	public native boolean waitForFileMask(String directrory, String fileMask);
    	public native boolean waitForAnyFile(String directrory);
    	public void Test() {
       		 }
     	public static void main(String [] args) {
    		Test t = new Test();
          		  /*Printf example*/
    			t.print("->Testing JNI - Hello from \n");
            		/*Loading a file as a byte array example*/
    			System.out.println("->Start Open  file Text.txt\n" + new String(t.readFile("Text.txt")));
       		  /*Printf example*/
    			t.print("->Finish Sample \n");
           		 }	
    }
    So you see that the package was not Test.java, these programs have changed as follows:
    (file path : C:\Tomcat5.5\webapps\ROOT\JNI\WEB-INF\classes\ver)
    /* Test .java*/
    package ver;
    public class Test {
        /*Load the dll that exports functions callable from java*/
        static {System.loadLibrary("TestImp");} /* Name Of DLL : TestImp.dll */
        /*Imported function declarations*/
    	public native void print(String msg);
    	public native byte[] readFile(String path);
    	public native int searchFile(String path, byte[] b, int bLength);
    	public native String[] findFiles(String path, String mask);
    	public native String[] checkProcess(String processName, boolean killIt, boolean printOutput);
    	public native int startProcess(String commandLine, String workingDir);
    	public native boolean waitForFileMask(String directrory, String fileMask);
    	public native boolean waitForAnyFile(String directrory);
    	public void Test() {
       		 }
    }
    And upper branches (file path : C:\Tomcat5.5\webapps\ROOT\JNI\WEB-INF\classes) made the following file:
    /*run.java*/
    import ver.*;
    import java.io.*;
    class usepackage{
    	public static void main(String [] args) {
    	Test  t = new Test ();
    	t.print(" JAVA ");
    	t.readFile("Text.txt");
    	}
    }
    After the Test. Java & run.java compile and run the following command and I got across the error:
    C:\Tomcat5.5\webapps\ROOT\JNI\WEB-INF\classes >java run
    Exception in thread "main" java.lang.UnsatisfiedLinkError: print
            at ver.callmydll.print(Native Method)
            at usepackage.main(usepackage.java:8)
    TestImp.dll Test.java file in System32 and the next there.
    How do you fix the error ???
    Email : m.hosseyni@ymail.com


  2. #2
    Administrator copeg's Avatar
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    Default Re: Using DLL in Java

    First, please do not double post your question. Your other post has been removed. Second, indicating someone to have private communications via email to solve your problem is against the whole idea of having public forums - so solutions to problems can facilitate someone else who has a similar problem in the future.

  3. #3
    Senile Half-Wit Freaky Chris's Avatar
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    Default Re: Using DLL in Java

    1) I have never tried to put my own DLL into System32 and load it with JNI.
    2) Are Servlets aloud to load DLLs?

    3) Are you sure that you have Compiled you C/C++ code correctly, is that code actually exporting the functions?


    Chris
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

  4. #4
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    Default Re: Using DLL in Java

    hi i have exactly the same issue please let me know if u fix that error mail me at ashok.jeev@live.in