jsp+Servlet编程实现验证码的方法

本文实例讲述了jsp+Servlet编程实现验证码的方法。分享给大家供大家参考，具体如下：

这里用到两个类，一个用于验证码实现，一个为后台Servlet验证输入是否正确：

CodeUtil.java--------验证码具体实现：

package util;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
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;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyContent;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageDecoder;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
public class CodeUtil extends HttpServlet {
 public void service(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  //System.out.println("哈哈哈");
  response.setContentType("image/jpeg");
  //设置页面不缓存
  response.setHeader("Pragma", "No-cache");
  response.setHeader("Cache-Control", "no-cache");
  response.setDateHeader("Expires", 0);
  //在内存中创建图像
  int width = 90;
  int height = 35;
  BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
  //获取图形上下文
  Graphics g = image.getGraphics();
  //随机类
  Random random = new Random();
  //设定背景
  g.setColor(getRandColor(200, 250));
  g.fillRect(0, 0, width, height);
  //设定字体
  g.setFont(new Font("Times New Roman",Font.PLAIN,30));
  //随机产生干扰线
  g.setColor(getRandColor(160, 200));
  for (int i = 0; i < 100; i++) {
   int x = random.nextInt(width);
   int y = random.nextInt(height);
   int xl = random.nextInt(12);
   int yl = random.nextInt(12);
   g.drawLine(x, y, x + xl, y + yl);
  }
  //随机产生4位验证码
  String[] codes = {"0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
  String code = "";
  for(int i=0;i<4;i++){
   String str = codes[random.nextInt(codes.length)];
   code += str;
   // 将认证码显示到图象中
   g.setColor(new Color(50 + random.nextInt(110), 20 + random.nextInt(110), 30 + random.nextInt(110)));
   //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
   g.drawString(str, 18 * i +13, 27); //文字间距*i+距离左边距，上边距
  }
  HttpSession session=request.getSession();
  // 将认证码存入SESSION
  session.setAttribute("code", code);
  // 图象生效
  g.dispose();
  // 输出图象到页面
  ImageIO.write(image, "JPEG", response.getOutputStream());
  //加上下面代码,运行时才不会出现java.lang.IllegalStateException: getOutputStream() has already been called ..........等异常
  response.getOutputStream().flush();
  response.getOutputStream().close();
  response.flushBuffer();
 }
 //获取随机颜色
 private Color getRandColor(int fc,int bc){
  Random random = new Random();
  if(fc>255) fc=255;
  if(bc>255) bc=255;
  int r = fc + random.nextInt(bc - fc);
  int g = fc + random.nextInt(bc - fc);
  int b = fc + random.nextInt(bc - fc);
  return new Color(r,g,b);
  }
}

CheckCodeUtil.java-----------用户输入验证功能

package util;
import java.io.IOException;
import java.io.PrintWriter;
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 CheckCodeUtil extends HttpServlet {
 public void service(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  request.setCharacterEncoding("utf-8");
  response.setContentType("text/html;charset=utf-8");
  PrintWriter out = response.getWriter();
  //从session获取验证码
  HttpSession session=request.getSession();
  String code=session.getAttribute("code").toString();
  System.out.println(code);
  //获取用户输入验证码
  String input=request.getParameter("code");
  System.out.println(input);
  if(code.equalsIgnoreCase(input)){
   //转发数据
   request.setAttribute("result", "true");
   request.getRequestDispatcher("test/regist.jsp").forward(request, response);
//   response.sendRedirect(request.getContextPath()+"/regist/regist.jsp");
  }else{
   request.setAttribute("result", "false");
   request.getRequestDispatcher("test/regist.jsp").forward(request, response);
  }
 }
}

测试页面效果：

测试页面代码：

<%@ page session="true" pageEncoding="utf-8" contentType="text/html; charset=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>
   function showResult1(){
   alert('输入正确');
   }
   function showResult2(){
   alert('输入错误');
   }
  </script>
 </head>
 <%
  response.setContentType("text/html;charset=utf-8");
  request.setCharacterEncoding("utf-8");
  String path=request.getContextPath();
  if(request.getAttribute("result")!=null){
  String result=request.getAttribute("result").toString();
  out.print(result);
  if(result.equals("true")){
   out.print("true");
   out.print("<script>showResult1();<script>");
  }else{
   out.print("<script>showResult2();<script>");
  }
  }
 %>
  <body>
  <br>验证码演示
  <form action="<%=path %>/checkCodeUtil" method="post">
  <input type="text" size="10" name="code"/>
  <img src="<%=path %>/codeUtil" id="img"/>
  <a href="javascript:;" onclick="document.
   getElementById('img').src='<%=path %>/codeUtil?'+new Date().getTime();">看不清，换一个</a>
  <input type="submit" value="提交">
  </form>
 </body>
</html>

希望本文所述对大家jsp程序设计有所帮助。