OpenCV unable to load library for a dynamic web project

Question

I am preparing a java web project on face recognition.I am using java library of opencv 2.4.7. when I am calling FaceDetector class from a servlet, it gives error-

java.lang.UnsatisfiedLinkError: no opencv_java247 in java.library.path java.lang.ClassLoader.loadLibrary(ClassLoader.java:1886) java.lang.Runtime.loadLibrary0(Runtime.java:849) java.lang.System.loadLibrary(System.java:1088) Models.NewFaceDetector.(NewFaceDetector.java:24) Servlets.helloServlet.doPost(helloServlet.java:108) javax.servlet.http.HttpServlet.service(HttpServlet.java:647) javax.servlet.http.HttpServlet.service(HttpServlet.java:728)

This code is working perfectly in console java project. Servlet Code is-

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    PrintWriter out=response.getWriter();
    Part name=request.getPart("NameBox");
    Part img=request.getPart("Img");
    String filename=getFileName(img);
    InputStream is=img.getInputStream();
    int i=is.available();
    byte[] b=new byte[i];
    is.read(b);
    String path="E:/temp/"+filename;
    FileOutputStream os=new FileOutputStream(path);
     os.write(b);
    os.close();
    is.close();
   FaceDetector fd=new FaceDetector();
    fd.getFaces(path);  
}

and my face detector class is-

public class FaceDetector {

static{ System.loadLibrary("opencv_java247"); }
public List<Mat> getFaces(String url) throws MalformedURLException, IOException
{
    List<Mat>faces=new ArrayList();
    Mat image = Highgui.imread(url);
    //code...
}

I gave the path to open cv dll- -Djava.library.path="C:\Users\vivek\Documents\NetBeansProjects\TrendFaceRecognizer\src\java\data"

I don't know what's wrong I am doing.

Sasi Kathimanda Sasi Kathimanda · Accepted Answer · 2013-12-31T07:37:17

How to resolve java.lang.UnsatisfiedLinkError
User should check whether-

System.loadLibrary is passed an incorrect parameter:
- Windows: To load Name.dll, Name is passed to the loadLibrary method.
  
  AIX, HP-UX, Solaris, Linux: To load libName.so or libName.a, libName is passed
  to the loadLibrary method
Native library is already loaded-

If the native library was already loaded by an application and the same
application tries to load it again, this can cause this error.
Native Library is not present in java.library.path or
LD_LIBRARY_PATH

Reference:Debugging java.lang.UnsatisfiedLinkError

and in your case, 1)check whether your servlet(might be in different package) that could access the dll in \TrendFaceRecognizer\src\java\data

2)Instead System.loadLibrary("opencv_java247") try using System.load("opencv_java247") .It seems loadLibrary uses default path and load will use absolute path

OpenCV unable to load library for a dynamic web project

1 Answers