01- Demand
Function implemented in Java code.
02- ideas
1) write a code generation tools.
2) in the preparation of a login page (verification code through, jump to the login page)
3) preparation of a jsp pages, for checking codes.
03- Code
ImageCodeServlet
package com.eleven;
import java.awt.Color;
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.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/servlet/ImageCodeServlet")
public class ImageCodeServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("UTF-8");
resp.setCharacterEncoding("UTF-8");
/**
* 生成带字符串的文本图片
*/
// 01创建图片缓存区
BufferedImage image = new BufferedImage(68, 22, BufferedImage.TYPE_INT_BGR); // 宽、高和图片类型
// 02创建绘制环境
Graphics paint = image.getGraphics();
Color c = new Color(200, 150, 255);
// 设置画笔
paint.setColor(c);
// 画背景
paint.fillRect(0, 0, 68, 22);
StringBuffer codes = new StringBuffer();
// 设置文本
char[] ch = "QWERTYUIOPASDFGHJKLZXCVBNM1234567890".toCharArray();
Random r = new Random(); // 随机数
int index;
for (int i = 0; i < 4; i++) {
index = r.nextInt(ch.length);
paint.setColor(new Color(r.nextInt(88), r.nextInt(150), r.nextInt(255))); // 设置文本颜色
paint.drawString(ch[index] + "", (i * 16) + 3, 18);
codes.append(ch[index]);
}
req.getSession().setAttribute("codes", codes);
//
// 03输出图片
ImageIO.write(image, "JPG", resp.getOutputStream());
}
}
LoginServlet
package com.eleven;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/servlet/LoginServlet")
public class LoginServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String codes = req.getSession().getAttribute("codes").toString();
String mycode = req.getParameter("checkcode");
resp.setCharacterEncoding("UTF-8");
req.setCharacterEncoding("UTF-8");
PrintWriter out = resp.getWriter();
if (mycode.toUpperCase().equals(codes)) {
out.println("验证码输入正确!");
} else {
out.println("验证码输入错误!");
}
out.flush();
out.close();
}
}
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>
<script type="text/javascript">
function reloadcode(){
var time = new Date().getTime();
document.getElementById("imagecode").src="servlet/ImageCodeServlet?d="+time;
}
</script>
</head>
<body>
<form action="servlet/LoginServlet" method="get">
验证码:<input type="text" name="checkcode">
<img alt="验证码" src="servlet/ImageCodeServlet" id="imagecode">
<a href="javascript:reloadcode();">看不清楚</a>
<input type="submit" value="验证">
</form>
</body>
</html>
04- demo
verification failed:
Verification is successful: