这是一个Servlet，名字是ImageServlet
package a;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class ImageServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
BufferedImage bfi = new BufferedImage(80,25,BufferedImage.TYPE_INT_RGB);
Graphics g = bfi.getGraphics();
g.fillRect(0, 0, 80, 25);
//验证码字符范围
char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".toCharArray();
Random r = new Random();
int index;
StringBuffer sb = new StringBuffer(); //保存字符串
for(int i=0; i<4; i++){
index = r.nextInt(ch.length);
g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
Font font = new Font("宋体", 30, 20);
g.setFont(font);
g.drawString(ch[index]+"", (i*20)+2, 23);
sb.append(ch[index]);
}
// 添加噪点
int area = (int) (0.02 * 80 * 25);
for(int i=0; i<area; ++i){
int x = (int)(Math.random() * 80);
int y = (int)(Math.random() * 25);
bfi.setRGB(x, y, (int)(Math.random() * 255));
}
//设置验证码中的干扰线
for (int i = 0; i < 6; i++) {
//随机获取干扰线的起点和终点
int xstart = (int)(Math.random() * 80);
int ystart = (int)(Math.random() * 25);
int xend = (int)(Math.random() * 80);
int yend = (int)(Math.random() * 25);
g.setColor(interLine(1, 255));
g.drawLine(xstart, ystart, xend, yend);
}
HttpSession session = request.getSession(); //保存到session
session.setAttribute("verificationCode", sb.toString());
ImageIO.write(bfi, "JPG", response.getOutputStream()); //写到输出流
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
private static Color interLine(int Low, int High){
if(Low > 255)
Low = 255;
if(High > 255)
High = 255;
if(Low < 0)
Low = 0;
if(High < 0)
High = 0;
int interval = High - Low;
int r = Low + (int)(Math.random() * interval);
int g = Low + (int)(Math.random() * interval);
int b = Low + (int)(Math.random() * interval);
return new Color(r, g, b);
}
}
接下来是一个jsp文件，先访问jsp文件。
<%@ 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>
<script type="text/javascript">
function reload(){
document.getElementById("image").src="<%=request.getContextPath() %>/imageServlet?date="+new Date().getTime();
$("#checkcode").val(""); // 将验证码清空
}
function verificationcode(){
var text=$.trim($("#checkcode").val());
$.post("${pageContext.request.contextPath}/verificationServlet",{op:text},function(data){
data=parseInt($.trim(data));
if(data>0){
$("#span").text("验证成功!").css("color","green");
}else{
$("#span").text("验证失败!").css("color","red");
reload(); //验证失败后需要更换验证码
}
});
$("#checkcode").val(""); // 将验证码清空
}
</script>
<body>
验证码：<input type="text" name="checkcode" id="checkcode"/>
<img src="<%=request.getContextPath() %>/ImageServlet" alt="验证码" id="image" />
<a href="reload();"><label>换一张</label></a><br>
<input type="button" value="提交" onclick="verificationcode();">
<span id="span"></span>
</body>
</html>