Challenge locating server resource :)

Question

Hi All,
I have written a servlet and accompanying javabean who's intended function is to determine image characteristics on the server. The characteristics that I am interested in are the images height and width in pixels.
I am using Tomcat version 5, and the images that I am interested in determining characteristics of are stored in the following directory location.
G:\Tomcat-5.5.9\webapps\ferngully\images\craftstamps\largeThe code that constitutes my image characteristics determining javabean is as follows:
package craftstamps;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.*;
import javax.imageio.ImageIO;
import javax.servlet.*;
import javax.servlet.http.*;
public class ImageCharacteristics
  private final String urlPrefix = "/ferngully/images/";
  private BufferedImage img;
  private int height;
  private int width;
  private URL imageURL;
  public ImageCharacteristics()
   * Locates and loads relevant image file.
   * @param imageSource Sets search location of image file
  public void setImageSource(ServletContext servCont, String imageSource)
    String imageLocation = urlPrefix + imageSource;
    System.out.println("Inside setImageSource(), selected image source is " +
                       imageLocation);
    try{
      imageURL = servCont.getResource(imageLocation);
      img = ImageIO.read(imageURL);
      height = img.getHeight();
      width = img.getWidth();
    }catch(IllegalArgumentException iae){
      System.out.println("IllegalArgumentException: " + iae.getMessage());
    }catch(IOException ioe){
      System.out.println("IOException reason: " + ioe.getMessage());
    }catch(NullPointerException npe){
      System.out.println("Null Pointer: " + npe.getMessage());
   * Determines the height of a given image file.
   * @return  Height of selected image as an int.
  public int getHeight()
    return height;
   * Determines the width of a given image file.
   * @return  Width of selected image as an int.
  public int getWidth()
    return width;
}The relevant servlet code used to access the desired characteristics is as follows:
ServletContext servCont = getServletContext();
String imageLocation = "craftstamps/large/" + productCode;
ImageCharacteristics imgCharacter = new ImageCharacteristics();
imgCharacter.setImageSource(servCont, imageLocation);
.....The "productCode" variable represents the name of the image (jpeg) that is to be characterized, e.g.:
S1_1G4BA.jpgWhen I run Tomcat I get the following exception report:
Inside setImageSource(), selected image source is /ferngully/images/craftstamps/
large/S1_1G4BA.jpg
IllegalArgumentException: input == null!The above error appears to be indicating that the server doesn't know where the image is located!
If anybody has any suggestions as to how I can fix this challenge they will be greatly appreciated.
Thanks
Kind Regards
Davo

Answer 1

"/" always refers to your context in j2ee web applications.
So if frengully is your context, then "/" will refer to the 'ferngully' folder which would be your web-root folder too incidentally.
This in turn means, your url-prefix in code ought to be as below.
private final String urlPrefix = "/images/";cheers,
ram.