生成随机验证码工具类

package com.web;
//验证码生成处理类
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;

import com.tools.MD5;

public class PictureCheckCode 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)){
                case 1:
                        tempInt=rand.nextInt(26)+65;
                        firstWord=String.valueOf((char)tempInt);
                        break;
                /*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=100;
        int height=40;
        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",MD5.code(randCode.toLowerCase()));
        
        g.dispose();
        
        ImageIO.write(image,"JPEG",response.getOutputStream());
        
    }

}