JAVA生成验证码

<img border="0"
                            src="ValidateCode"
                            id='code' width="64" height="30" 
                            style="vertical-align: top; cursor: pointer;"
                             title="点击刷新验证码" />

JAVA代码：

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 ValidateCode extends HttpServlet {

     private static final long serialVersionUID = 1L;
     
     private Random rand=new Random();
     
     
     /**
      * 生成随机颜色
      * 
      * @param   start  [int]
      * @param   end    [int]
      * @return  Color  [object]
      */
     public Color getRandColor(int start,int end){
      int randNum;
      if(start>255) start=255;
      if(end>255) end=255;
      if(start>end) randNum=start-end;
      else randNum=end-start;
      int r=start+rand.nextInt(randNum); 
      int g=start+rand.nextInt(randNum);
      int b=start+rand.nextInt(randNum);
      return new Color(r,g,b);
     }
     
     /**
      * 着色\旋转\缩放
      * 
      * @param word 文字
      * @param g    图片对象
      */
     public void coloredAndRotation(String word,int i,Graphics g){
      /**着色**/
      g.setColor(new Color(20+rand.nextInt(110),20+rand.nextInt(110),20+rand.nextInt(110)));
      /**旋转**/
      Graphics2D g2d=(Graphics2D)g;
      AffineTransform trans=new AffineTransform();
      trans.rotate(rand.nextInt(45)*3.14/180,15*i+8,7);
      /**缩放**/
      float scaleSize=rand.nextFloat()+0.8f;
      if(scaleSize>1f) scaleSize=1f;
      trans.scale(scaleSize, scaleSize);
      g2d.setTransform(trans);
      g.drawString(word,15*i+20,20);
     }
     
     /**
      * 生成100条干扰线
      * 
      * @param g2d
      * @param width
      * @param height
      */
     public void getRandLine(Graphics2D g2d,int width,int height){
      for(int i=0;i<100;i++){
       int x=rand.nextInt(width-1);
       int y=rand.nextInt(height-1);
       int z=rand.nextInt(6)+1;
       int w=rand.nextInt(12)+1;
       
       BasicStroke bs=new BasicStroke(2f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL);
       Line2D line=new Line2D.Double(x,y,x+z,y+w);
       g2d.setStroke(bs);
       g2d.draw(line);
      }
     }
     
     /**
      * 获取随机文字
      * @param  length [int]        验证码长度
      * @param  g      [Graphics]   图片对象
      * @return String
      * @case1:A-Z
      * @case2:chinese
      * @default:0-9
      */
     @SuppressWarnings("unused")
     public String getRandWord(int length,Graphics g){
      String finalWord="",firstWord="";
      int tempInt=0;
      String[] array={
        "0","1","2","3",
        "4","5","6","7",
        "8","9","a","b",
        "c","d","e","f"};
      
      for(int i=0;i<length;i++){
       switch(rand.nextInt(2)){
       //英文数字混合
       /* case 1:
          tempInt=rand.nextInt(26)+65;
          firstWord=String.valueOf((char)tempInt);
          break;*/
       //纯数字
        case 2:
          int r1,r2,r3,r4;
          String strH,strL;//high&low
          r1=rand.nextInt(3)+11; //前闭后开[11,14)
          if(r1==13){
           r2=rand.nextInt(7);
          }else{
           r2=rand.nextInt(16);
          }
          
          r3=rand.nextInt(6)+10;
          if(r3==10){
           r4=rand.nextInt(15)+1;
          }else if(r3==15){
           r4=rand.nextInt(15);
          }else{
           r4=rand.nextInt(16);
          }
          
          strH=array[r1]+array[r2];
          strL=array[r3]+array[r4];
          
          byte[] bytes=new byte[2];
          bytes[0]=(byte)(Integer.parseInt(strH,16));
          bytes[1]=(byte)(Integer.parseInt(strL,16));
          
          firstWord=new String(bytes);
          break;
        default:
          tempInt=rand.nextInt(10)+48;
          firstWord=String.valueOf((char)tempInt);
          break;
       }
       finalWord+=firstWord;
       this.coloredAndRotation(firstWord,i, g);
      }
      
      return finalWord;
     }

     protected void service(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException {
      
      //设制不缓存图片
      response.setHeader("Pragma","No-cache");
      response.setHeader("Cache-Control","No-cache");
      response.setDateHeader("Expires",0);
      
      //生成图片
      response.setContentType("image/jpeg");
      int width=80;
      int height=30;
      BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
      
      Graphics g=image.getGraphics();
      Graphics2D g2d=(Graphics2D)g;
      Font mFont=new Font("宋体",Font.BOLD,22);
      g.setColor(this.getRandColor(200,250));
      g.fillRect(0, 0, width, height);
      g.setFont(mFont);
      g.setColor(this.getRandColor(180,200));
      
      this.getRandLine(g2d, width, height);
      
      String randCode=this.getRandWord(4, g);
      
      HttpSession session=request.getSession();
      session.setAttribute("randCode",randCode);
      
      g.dispose();
      
      ImageIO.write(image,"JPEG",response.getOutputStream());
      
     }
}