servlet的代碼：
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
@SuppressWarnings("serial")
public class IdentityServlet extends HttpServlet {
public static final char[] chs = {'2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K',
'L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z'};
public static Random random = new Random();
public static String getRandomString(){
StringBuffer buffer = new StringBuffer();
for (int i = 0; i < 6; i++) {
buffer.append(chs[random.nextInt(chs.length)]);
}
return buffer.toString();
}
public static Color getRandomColor(){
return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
}
public static Color getReverseColor(Color c){
return new Color(255-c.getRed(),255-c.getGreen(),255-c.getBlue());
}
public void doGet(HttpServletRequest req , HttpServletResponse resp ) throws IOException {
resp.setContentType("image/jpeg");
String randomString = getRandomString();
req.getSession(true).setAttribute("randomString" , randomString);
int width = 100;
int height = 30;
Color color = getRandomColor();
Color reverse = getReverseColor(color);
BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D g = bi.createGraphics();
g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));
g.setColor(color);
g.fillRect(0, 0, width, height);
g.setColor(reverse);
g.drawString(randomString, 18, 20);
for (int i = 0 , n = random.nextInt(100); i < n; i++) {
g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
}
ServletOutputStream out = resp.getOutputStream();
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(bi);
out.flush();
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>LoginServlet</display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>identity</servlet-name>
<servlet-class>com.qf.servlet.IdentityServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>identity</servlet-name>
<url-pattern>/identity</url-pattern>
</servlet-mapping>
</web-app>index.jsp
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<script type="text/javascript">
function reloadImage(){
document.getElementById('btn').disabled = true;
document.getElementById('identity').src = 'identity';
}
</script>
<img onLoad = "" src="identity" id="identity" />
<input type="submit" value="提交" id="btn" onclick="reloadImage();">
</body>
</html>