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"/> <img src="<%=path %>/codeUtil"/> <a href="javascript:;">看不清，换一个</a> <input type="submit" value="提交"> </form> </body> </html>