java使用servlet实现验证码

利用servlet 实现验证码主要继承httpservlet类

package com.zyc.demo; 
 
import java.awt.color; 
import java.awt.font; 
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.http.httpservlet; 
import javax.servlet.http.httpservletrequest; 
import javax.servlet.http.httpservletresponse; 
import javax.servlet.http.httpsession; 
 
public class drewimage extends httpservlet{ 
  /** 
   * 
   */ 
  private static final long serialversionuid = 1505032428319459075l; 
  private final font mfont = 
      new font("arial black", font.plain, 16); 
    private final int img_width = 100; 
    private final int img_heigth = 18; 
    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); 
    } 
    public void service(httpservletrequest request, 
      httpservletresponse response) 
      throws servletexception, ioexception 
    { 
      response.setheader("pragma","no-cache"); 
      response.setheader("cache-control","no-cache"); 
      response.setdateheader("expires", 0); 
      response.setcontenttype("image/jpeg"); 
      bufferedimage image = new bufferedimage 
        (img_width , img_heigth , bufferedimage.type_int_rgb); 
      graphics g = image.getgraphics(); 
      random random = new random(); 
      g.setcolor(getrandcolor(200 , 250)); 
      g.fillrect(1, 1, img_width - 1, img_heigth - 1); 
      g.setcolor(new color(102 , 102 , 102)); 
      g.drawrect(0, 0, img_width - 1, img_heigth - 1); 
      g.setcolor(getrandcolor(160,200)); 
      for (int i = 0 ; i < 30 ; i++) 
      { 
        int x = random.nextint(img_width - 1); 
        int y = random.nextint(img_heigth - 1); 
        int xl = random.nextint(6) + 1; 
        int yl = random.nextint(12) + 1; 
        g.drawline(x , y , x + xl , y + yl); 
      } 
      g.setcolor(getrandcolor(160,200)); 
      for (int i = 0 ; i < 30 ; i++) 
      { 
        int x = random.nextint(img_width - 1); 
        int y = random.nextint(img_heigth - 1); 
        int xl = random.nextint(12) + 1; 
        int yl = random.nextint(6) + 1; 
        g.drawline(x , y , x - xl , y - yl); 
      } 
      g.setfont(mfont); 
      string srand = ""; 
      for (int i = 0 ; i < 4 ; i++) 
      { 
        string tmp = getrandomchar(); 
        srand += tmp; 
        g.setcolor(new color(20 + random.nextint(110) 
          ,20 + random.nextint(110) 
          ,20 + random.nextint(110))); 
        g.drawstring(tmp , 15 * i + 10,15); 
      } 
      httpsession session = request.getsession(true); 
      session.setattribute("rand" , srand); 
//     system.out.println("写入session"+srand); 
      g.dispose(); 
      imageio.write(image, "jpeg", response.getoutputstream()); 
    } 
    private string getrandomchar() 
    { 
      int rand = (int)math.round(math.random() * 2); 
      long itmp = 0; 
      char ctmp = '\u0000'; 
      switch (rand) 
      { 
        case 1: 
          itmp = math.round(math.random() * 25 + 65); 
          ctmp = (char)itmp; 
          return string.valueof(ctmp); 
        case 2: 
          itmp = math.round(math.random() * 25 + 97); 
          ctmp = (char)itmp; 
          return string.valueof(ctmp); 
        default : 
          itmp = math.round(math.random() * 9); 
          return itmp + ""; 
      } 
    } 
} 

下面是web.xml 配置

<?xml version="1.0" encoding="utf-8"?> 
<web-app xmlns:xsi="http://www.w3.org/2001/xmlschema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemalocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="webapp_id" version="3.0"> 
 <display-name>industrydemo</display-name> 
 <welcome-file-list> 
  <welcome-file>index.html</welcome-file> 
  <welcome-file>index.htm</welcome-file> 
  <welcome-file>index.jsp</welcome-file> 
  <welcome-file>default.html</welcome-file> 
  <welcome-file>default.htm</welcome-file> 
  <welcome-file>default.jsp</welcome-file> 
 </welcome-file-list> 
  
 <servlet> 
   <servlet-name>img</servlet-name> 
   <servlet-class>com.zyc.demo.drewimage</servlet-class> 
 </servlet> 
  
 <servlet-mapping> 
   <servlet-name>img</servlet-name> 
   <url-pattern>/img.do</url-pattern> 
 </servlet-mapping> 
  
</web-app> 

 jsp 文件

<%@ page language="java" import="java.util.*" pageencoding="utf-8"%> 
<% 
string path = request.getcontextpath(); 
string basepath = request.getscheme()+"://"+request.getservername()+":"+request.getserverport()+path+"/"; 
%> 
 
<!doctype html public "-//w3c//dtd html 4.01 transitional//en"> 
<html> 
 <head> 
  <base href="<%=basepath%>"> 
   
  <title>my jsp 'yanzhengma.jsp' starting page</title> 
   
  <meta http-equiv="pragma" content="no-cache"> 
  <meta http-equiv="cache-control" content="no-cache"> 
  <meta http-equiv="expires" content="0">   
  <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 
  <meta http-equiv="description" content="this is my page"> 
  <!-- 
  <link rel="stylesheet" type="text/css" href="styles.css"> 
  --> 
 
 </head> 
  
 <body> 
  <img alt="验证码" src="img.do"> <button onclick="window.location.reload();">刷新</button> 
 </body> 
</html> 

简单实用。

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