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。