import java.awt.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class ChainImageSource extends HttpServlet {

  int keynum = 0;  // used to create a unique key

  public void doGet(HttpServletRequest req, HttpServletResponse res)
                               throws ServletException, IOException {
    // Get an Image
    String imageFile = req.getRealPath("/system/images/serverduke.gif");
    Image image = Toolkit.getDefaultToolkit().getImage(imageFile);

    // Create a unique key under which to store the image
    String key = "com.oreilly.servlet.ChainImageSource." + keynum++;

    // Store the image in the system Properties list using that key
    System.getProperties().put(key, image);

    // Tell the next servlet to expect an image key
    res.setContentType("java-internal/image-key");

    PrintWriter out = res.getWriter();

    // Send the key
    out.println(key);
  }
}