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Servlet之HttpSession验证码

2015-11-04 00:00 543 查看
摘要: Servlet之HttpSession验证码

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>
<font color="red">
<%=session.getAttribute("message")==null?"":session.getAttribute("message")%>
</font>
<form action="<%=request.getContextPath() %>/checkCodeServlet" method="post">
name:<input type="text" name="name"/>
checkCode:<input type="text" name="CHECK_CODE_PARAM_NAME"/>
<img alt="" src="<%=request.getContextPath() %>/validateColorServlet">
<input type="submit" value="Submit">
</form>
</body>
</html>

CheckCodeServlet
import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* Servlet implementation class CheckCodeServlet
*/
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

public CheckCodeServlet() {
super();
}

protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

String paramCode = request.getParameter("CHECK_CODE_PARAM_NAME");

String sessionCode = (String) request.getSession().getAttribute("CHECK_CODE_KEY");

System.out.println(paramCode);
System.out.println(sessionCode);

if(!(paramCode!=null && paramCode.equals(sessionCode))){

request.getSession().setAttribute("message", "验证码不一致");
response.sendRedirect(request.getContextPath()+"/check/index.jsp");
return;
}

System.out.println("456789");
}

}

ValidateColorServlet

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.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* Servlet implementation class ValidateColorServlet
*/
@WebServlet("/validateColorServlet")
public class ValidateColorServlet extends HttpServlet {

public static final String CHECK_CODE_KEY = "CHECK_CODE_KEY";

private static final long serialVersionUID = 1L;

//设置验证图片的宽度, 高度, 验证码的个数
private int width = 152;
private int height = 40;
private int codeCount = 4;

//验证码字体的高度
private int fontHeight = 4;

//验证码中的单个字符基线. 即：验证码中的单个字符位于验证码图形左上角的 (codeX, codeY) 位置处
private int codeX = 0;
private int codeY = 0;

//验证码由哪些字符组成
char [] codeSequence = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz23456789".toCharArray();

//初始化验证码图形属性
public void init(){
fontHeight = height - 2;
codeX = width / (codeCount + 2);
codeY = height - 4;
}

public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//定义一个类型为 BufferedImage.TYPE_INT_BGR 类型的图像缓存
BufferedImage buffImg = null;
buffImg = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);

//在 buffImg 中创建一个 Graphics2D 图像
Graphics2D graphics = null;
graphics = buffImg.createGraphics();

//设置一个颜色, 使 Graphics2D 对象的后续图形使用这个颜色
graphics.setColor(Color.WHITE);

//填充一个指定的矩形: x - 要填充矩形的 x 坐标; y - 要填充矩形的 y 坐标; width - 要填充矩形的宽度; height - 要填充矩形的高度
graphics.fillRect(0, 0, width, height);

//创建一个 Font 对象: name - 字体名称; style - Font 的样式常量; size - Font 的点大小
Font font = null;
font = new Font("", Font.BOLD, fontHeight);
//使 Graphics2D 对象的后续图形使用此字体
graphics.setFont(font);

graphics.setColor(Color.BLACK);

//绘制指定矩形的边框, 绘制出的矩形将比构件宽一个也高一个像素
graphics.drawRect(0, 0, width - 1, height - 1);

//随机产生 15 条干扰线, 使图像中的认证码不易被其它程序探测到
Random random = null;
random = new Random();
graphics.setColor(Color.GREEN);
for(int i = 0; i < 55; i++){
int x = random.nextInt(width);
int y = random.nextInt(height);
int x1 = random.nextInt(20);
int y1 = random.nextInt(20);
graphics.drawLine(x, y, x + x1, y + y1);
}

//创建 randomCode 对象, 用于保存随机产生的验证码, 以便用户登录后进行验证
StringBuffer randomCode;
randomCode = new StringBuffer();

for(int i = 0; i < codeCount; i++){
//得到随机产生的验证码数字
String strRand = null;
strRand = String.valueOf(codeSequence[random.nextInt(36)]);

//把正在产生的随机字符放入到 StringBuffer 中
randomCode.append(strRand);

//用随机产生的颜色将验证码绘制到图像中
graphics.setColor(Color.BLUE);
graphics.drawString(strRand, (i + 1)* codeX, codeY);
}

//再把存放有所有随机字符的 StringBuffer 对应的字符串放入到 HttpSession 中
request.getSession().setAttribute(CHECK_CODE_KEY, randomCode.toString());

//禁止图像缓存
response.setHeader("Pragma", "no-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);

//将图像输出到输出流中
ServletOutputStream sos = null;
sos = response.getOutputStream();
ImageIO.write(buffImg, "jpeg", sos);
sos.close();
}
}
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