登录 验证码的实现 --代码

实现验证码
jsp文件

function refresh(obj){
 obj.src="PictureCheckCode?id="+Math.random();
 
}

<tr>
   <th>验证码</th>
   <td width="120"><div class="input_num"><input name="codeImage" type="text" /></div></td>
   <td width="156"><div id="imagecode">
   <img src="PictureCheckCode" id="CreateCheckCode" onclick="refresh(this)" align="middle" width="86" height="26" title="点击刷新" />
   </div></td>
 </tr>
 
 web.xml文件

  <servlet>
    <servlet-name>PictureCheckCode</servlet-name>
    <servlet-class>com.wondersgroup.wssip.local.application.login.PictureCheckCode</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>PictureCheckCode</servlet-name>
    <url-pattern>/PictureCheckCode</url-pattern>
  </servlet-mapping>
 
 PictureCheckCode.java 文件
 
package com.wondersgroup.wssip.local.application.login;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.geom.Line2D;
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 PictureCheckCode extends HttpServlet {

 private static final long serialVersionUID = 1L;

 public PictureCheckCode() {
  super();
 }

 public void destroy() {
  super.destroy();
 }

 public void init() throws ServletException {
  super.init();
 }
 /*该方法主要作用是获得随机生成的颜色*/
 public Color getRandColor(int s,int e){
  Random random=new Random ();
  if(s>255) s=255;
  if(e>255) e=255;
  int r,g,b;
  r=s+random.nextInt(e-s); //随机生成RGB颜色中的r值
  g=s+random.nextInt(e-s); //随机生成RGB颜色中的g值
  b=s+random.nextInt(e-s); //随机生成RGB颜色中的b值
  return new Color(r,g,b);
 }

 @Override
 public void service(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  //设置不缓存图片
  response.setHeader("Pragma", "No-cache");
  response.setHeader("Cache-Control", "No-cache");
  response.setDateHeader("Expires", 0);
  //指定生成的响应图片,一定不能缺少这句话,否则错误.
  response.setContentType("image/jpeg");
  int width=86,height=30;  //指定生成验证码的宽度和高度
  BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //创建BufferedImage对象,其作用相当于一图片
  Graphics g=image.getGraphics();  //创建Graphics对象,其作用相当于画笔
  Graphics2D g2d=(Graphics2D)g;  //创建Grapchics2D对象
  Random random=new Random();
  Font mfont=new Font("楷体",Font.BOLD,23); //定义字体样式
  g.setColor(getRandColor(200,250));
  g.fillRect(0, 0, width, height); //绘制背景
  g.setFont(mfont);     //设置字体
  
  
  //绘制100条颜色和位置全部为随机产生的线条,该线条为2f
  for(int i=0;i<200;i++){
   g.setColor(getRandColor(100,200));
   int x=random.nextInt(width-1);
   int y=random.nextInt(height-1);
   int x1=1;
   int y1=1;
   BasicStroke bs=new BasicStroke(2f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL); //定制线条样式
   Line2D line=new Line2D.Double(x,y,x+x1,y+y1);
   g2d.setStroke(bs);
   g2d.draw(line);  //绘制直线
   
  }
  //输出由英文，数字，和中文随机组成的验证文字，具体的组合方式根据生成随机数确定。
  String sRand="";
  String ctmp="";
  int itmp=0;
  //制定输出的验证码为四位
  for(int i=0;i<4;i++){
   switch(random.nextInt(2)){
    case 1:  //生成A-Z的字母
         itmp=random.nextInt(26)+65;
         ctmp=String.valueOf((char)itmp);
         break;
//    case 2:  //生成汉字
//      String[] rBase={"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};
//      //生成第一位区码
//      int r1=random.nextInt(3)+11;
//      String str_r1=rBase[r1];
//      //生成第二位区码
//      int r2;
//      if(r1==13){
//       r2=random.nextInt(7); 
//      }else{
//       r2=random.nextInt(16);
//      }
//      String str_r2=rBase[r2];
//      //生成第一位位码
//      int r3=random.nextInt(6)+10;
//      String str_r3=rBase[r3];
//      //生成第二位位码
//      int r4;
//      if(r3==10){
//       r4=random.nextInt(15)+1;
//      }else if(r3==15){
//       r4=random.nextInt(15);
//      }else{
//       r4=random.nextInt(16);
//      }
//      String str_r4=rBase[r4];
//      //将生成的机内码转换为汉字
//      byte[] bytes=new byte[2];
//      //将生成的区码保存到字节数组的第一个元素中
//      String str_12=str_r1+str_r2;
//      int tempLow=Integer.parseInt(str_12, 16);
//      bytes[0]=(byte) tempLow;
//      //将生成的位码保存到字节数组的第二个元素中
//      String str_34=str_r3+str_r4;
//      int tempHigh=Integer.parseInt(str_34, 16);
//      bytes[1]=(byte)tempHigh;
//      ctmp=new String(bytes);
//      break;
    default:
      itmp=random.nextInt(10)+48;
      ctmp=String.valueOf((char)itmp);
      break;
   }
   sRand+=ctmp;
   Color color=new Color(20+random.nextInt(110),20+random.nextInt(110),random.nextInt(110));
   g.setColor(color);
   //将生成的随机数进行随机缩放并旋转制定角度 PS.建议不要对文字进行缩放与旋转,因为这样图片可能不正常显示
   /*将文字旋转制定角度*/
   Graphics2D g2d_word=(Graphics2D)g;
   AffineTransform trans=new AffineTransform();
   trans.rotate((45)*3.14/180,15*i+8,7);
   /*缩放文字*/
   float scaleSize=random.nextFloat()+0.8f;
   if(scaleSize>1f) scaleSize=1f;
   trans.scale(scaleSize, scaleSize);
   g2d_word.setTransform(trans);
   g.drawString(ctmp, 15*i+18, 14);
  }
  HttpSession session=request.getSession(true);
  session.setAttribute("randCheckCode", sRand);
  g.dispose(); //释放g所占用的系统资源
  ImageIO.write(image,"JPEG",response.getOutputStream()); //输出图片
 }
}