imagefilter.java

icsamples目录中有icsamples网络程序。 这个程序包括J2EE网络层的范例程序

package jwadbook.filter;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.ServletException;
import java.io.*;
import java.util.Date;
import java.awt.*;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
import java.awt.image.BufferedImage;

/**
 *
 * @author Jian (James) Cai
 */
public class ImageFilter implements Filter
{
    FilterConfig filterConfig;
    
    public void init(final FilterConfig fConf) 
    {
        filterConfig = fConf;
    }

    public void destroy()
    {
    }
    
    public void doFilter(final ServletRequest request, final ServletResponse response, FilterChain chain) throws java.io.IOException,
    javax.servlet.ServletException
    {
	String message = "FilterMessage";
	GenericResponseWrapper wrapper = new GenericResponseWrapper((HttpServletResponse)response);
	chain.doFilter(request, wrapper);
	OutputStream out = response.getOutputStream();
	message = filterConfig.getInitParameter("message");

	if (contentIsUncachedImage(wrapper) && message != null)
	    {
		ByteArrayOutputStream imageStream = manipulateImage(message, wrapper.output());
		response.setContentLength(imageStream.size());
		response.setContentType("image/jpeg");
		out.write(imageStream.toByteArray());
	    }
	else
	    {
		out.write(wrapper.output());
	    }
	out.flush();
	out.close();
    }
    
    public boolean contentIsUncachedImage(GenericResponseWrapper wrapper){
	if(wrapper.getContentType()!=null)
	    {
		if(wrapper.getContentType().startsWith("image/"))
		    {
			if(wrapper.output().length>0){
			    return true;
			}
		}
	}
	return false;
    }
    
    
    public ByteArrayOutputStream manipulateImage(String message, byte[] imageData) throws ServletException
    {
	ByteArrayOutputStream imageStream;
	Frame frame=null;
	Graphics graphics=null;
	try
	    {
		frame = new Frame();
		frame.addNotify();
		MediaTracker mt = new MediaTracker(frame); // frame acts as an ImageObserver
		Image image = Toolkit.getDefaultToolkit().createImage(imageData);
		mt.addImage(image, 0);
		mt.waitForAll();
		int w = image.getWidth(frame);
		int h = image.getHeight(frame);
		BufferedImage offscreen = new BufferedImage(w,h,BufferedImage.TYPE_3BYTE_BGR);
		graphics = offscreen.getGraphics();
		graphics.drawImage(image, 0, 0, frame);
		graphics.setColor(Color.white);
		graphics.setFont(new Font("Arial", Font.BOLD | Font.ITALIC, 20));
		graphics.drawString(message, 9, 29);
		graphics.setColor(Color.black);
		graphics.drawString(message, 10, 30);
		imageStream = new ByteArrayOutputStream();
		JPEGImageEncoder encoder=com.sun.image.codec.jpeg.JPEGCodec.createJPEGEncoder(imageStream);
		encoder.encode(offscreen);
	    }
	catch (InterruptedException e)
	    {
		throw new ServletException(e.getMessage());
	    }
	catch (IOException e)
	    {
		throw new ServletException(e.getMessage());
	    }
	finally
	    {
		if (graphics != null)
		    {
			graphics.dispose();
		    }
		if (frame != null)
		    {
			frame.removeNotify();
		    }
	    }
	return imageStream;
    }
}