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

 
 
 IndustryDemo 
  
  index.html 
  index.htm 
  index.jsp 
  default.html 
  default.htm 
  default.jsp 
  
  
  
   img 
   com.zyc.demo.DrewImage 
  
  
  
   img 
   /img.do 
  
  
 

 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+"/"; 
%> 
 
 
 
  
   
   
   
   
   
   
     
   
   
   
 
  
  
  
   刷新 
  
 

简单实用。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持考高分网。