ImageIO.write(image, "png", servletOutputStream)

ImageIO.jsp

<%@ page contentType="image/jpeg" %><%@ page import="javax.imageio.*"%><%@ page import="java.io.*"%><%@ page import="java.awt.*"%><%@ page import="java.awt.image.*"%><%
BufferedImage image= new BufferedImage(500,500, BufferedImage.TYPE_INT_RGB);
Graphics g=image.getGraphics();
g.setColor(Color.GREEN);
g.fillRect(0,0,400,300);

ServletOutputStream sos = response.getOutputStream();
ImageIO.write(image, "gif", sos);

%>