Tip

Generating dynamic images using servlet

Servlet ImageGenerator shows how easily can servlet on Domino server produce dynamic images. Images are generated using Acme?s classes, that are part of notes.jar package.

For keeping this example simple, there is no parametrization as well as no caching mechanism implemented.


CODE:
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.awt.*;
import Acme.JPM.Encoders.*;
import lotus.domino.*;

public class ImageGenerator extends HttpServlet
{
Image image = null;
public static final int IMAGE_WIDTH = 200;
public static final int IMAGE_HEIGHT = 40;

//Initialize global variables
public void init(ServletConfig config) throws ServletException
{
super.init(config);
// use temporary frame to get new image
Frame frameTemp = new Frame();
frameTemp.addNotify();
image = frameTemp.createImage(IMAGE_WIDTH, IMAGE_HEIGHT);
}

//Process HTTP Get request
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
response.setContentType("image/gif");
OutputStream os = response.getOutputStream();
// write GIF to output stream
writeImage(os, image);
os.close();
}

private void writeImage(OutputStream out, Image image) throws IOException
{
Graphics g = image.getGraphics();

// >> PLACE YOUR RENDERING CODE HERE <<

// Example - START
try
{
NotesThread.sinitThread();
Session s = NotesFactory.createSession();
g.setColor(Color.orange);
g.fillRect(0, 0, IMAGE_WIDTH, IMAGE_HEIGHT);
g.setColor(Color.black);
g.drawString(s.getPlatform(), 6, 15);
}
catch (Exception e)
{
g.drawString("" + e, 6, 15);
}
// Example - END

GifEncoder encoder = new GifEncoder(image, out);
encoder.encode();
out.flush();
}

}

This was first published in November 2000

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