JAVA技术：代码实现验证码图片的生成

1   package  com.logcd.servlet;  
2    
3   import  java.awt.Color;  
4   import  java.awt.Font;  
5   import  java.awt.Graphics2D;  
6   import  java.awt.image.BufferedImage;  
7   import  java.util.Random;  
8   import  javax.imageio.ImageIO;  
9   import  javax.servlet. * ; 
10   import  java.io. * ; 
11   import  javax.servlet.http. * ; 
12   import  javax.servlet.ServletException; 
13   import  javax.servlet.http.HttpServlet; 
14   import  javax.servlet.http.HttpServletRequest; 
15   import  javax.servlet.http.HttpServletResponse; 
16   
17  @SuppressWarnings( " serial " ) 
18   public   class  RandomCode  extends  HttpServlet { 
19   
20       public   void  doGet(HttpServletRequest request, HttpServletResponse response) 
21               throws  ServletException, IOException { 
22   
23           this .doPost(request, response); 
24      } 
25   
26       public   void  doPost(HttpServletRequest request, HttpServletResponse response) 
27               throws  ServletException, IOException { 
28   
29           //  验证码图片的宽度。 
30           int  width  =   70 ; 
31           //  验证码图片的高度。 
32           int  height  =   30 ; 
33          BufferedImage buffImg  =   new  BufferedImage(width, height,  34                  BufferedImage.TYPE_INT_RGB); 
35          Graphics2D g  =  buffImg.createGraphics(); 
36   
37           //  创建一个随机数生成器类。 38         Random random = new Random(); 39  40          //  设定图像背景色(因为是做背景，所以偏淡) 
41          g.setColor(getRandColor( 200 ,  250 )); 
42          g.fillRect( 0 ,  0 , width, height); 
43           //  创建字体，字体的大小应该根据图片的高度来定。 
44          Font font  =   new  Font( " Times New Roman " , Font.HANGING_BASELINE,  28 );  45           //  设置字体。 
46          g.setFont(font);  47    48           //  画边框。 49         g.setColor(Color.BLACK); 50         g.drawRect(0, 0, width - 1, height - 1); 
51           //  随机产生155条干扰线，使图象中的认证码不易被其它程序探测到。 
52   // g.setColor(Color.GRAY); 
53          g.setColor(getRandColor( 160 , 200 )); 
54           for  ( int  i  =   0 ; i  <   155 ; i ++ ) { 
55               int  x  =  random.nextInt(width); 
56               int  y  =  random.nextInt(height); 
57               int  xl  =  random.nextInt( 12 ); 
58               int  yl  =  random.nextInt( 12 ); 
59              g.drawLine(x, y, x  +  xl, y  +  yl); 
60          } 
61   
62           //  randomCode用于保存随机产生的验证码，以便用户登录后进行验证。 
63          StringBuffer randomCode  =   new  StringBuffer(); 
64   
65           //  设置默认生成4个验证码 
66           int  length  =   4 ; 
67           //  设置备选验证码:包括"a-z"和数字"0-9" 68         String base = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; 
69   
70           int  size  =  base.length(); 
71   
72           //  随机产生4位数字的验证码。 
73           for  ( int  i  =   0 ; i  <  length; i ++ ) {  74               //  得到随机产生的验证码数字。 75             int start = random.nextInt(size); 
76              String strRand  =  base.substring(start, start  +   1 ); 
77   
78               //  用随机产生的颜色将验证码绘制到图像中。 
79   //  生成随机颜色(因为是做前景，所以偏深) 80  // g.setColor(getRandColor(1, 100)); 81              
82   // 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成 
83              g.setColor( new  Color( 20 + random.nextInt( 110 ), 20 + random.nextInt( 110 ), 20 + random.nextInt( 110 ))); 
84   
85              g.drawString(strRand,  15   *  i  +   6 ,  24 ); 
86   
87               //  将产生的四个随机数组合在一起。 
88              randomCode.append(strRand); 
89          } 
90           //  将四位数字的验证码保存到Session中。 
91          HttpSession session  =  request.getSession(); 
92          session.setAttribute( " rand " , randomCode.toString()); 
93   
94           // 图象生效 
95          g.dispose(); 
96   
97           //  禁止图像缓存。 
98          response.setHeader( " Pragma " ,  " no-cache " ); 
99          response.setHeader( " Cache-Control " ,  " no-cache " );
100          response.setDateHeader( " Expires " ,  0 );
101  
102          response.setContentType( " image/jpeg " );
103  
104           //  将图像输出到Servlet输出流中。105         ServletOutputStream sos = response.getOutputStream();
106          ImageIO.write(buffImg,  " jpeg " , sos);
107          sos.flush();
108          sos.close();
109  
110      }
111  
112      Color getRandColor( int  fc,  int  bc) { //  给定范围获得随机颜色
113          Random random  =   new  Random();
114           if  (fc  >   255 )
115              fc  =   255 ;
116           if  (bc  >   255 )
117              bc  =   255 ;
118           int  r  =  fc  +  random.nextInt(bc  -  fc);
119           int  g  =  fc  +  random.nextInt(bc  -  fc);
120           int  b  =  fc  +  random.nextInt(bc  -  fc);
121           return   new  Color(r, g, b);
122      }
123  
124  }

1       < servlet >
2           < servlet - name > RandomCode </ servlet - name >
3           < servlet - class > com.logcd.servlet.RandomCode </ servlet - class >
4       </ servlet >
5       < servlet - mapping >
6           < servlet - name > RandomCode </ servlet - name >
7           < url - pattern >/ randomCode </ url - pattern >
8       </ servlet - mapping >

1   < meta http - equiv = " Content-Type "  content = " text/html; charset=gb2312 "   />  
2   < meta http - equiv = " pragma "  content = " no-cache " />  
3   < meta http - equiv = " cache-control "  content = " no-cache " />  
4   < meta http - equiv = " expires "  content = " 0 " />  
5   
6   < iframe src = " http://127.0.0.1/js_test/randomCode "  id = " codeFrame "  name = " codeFrame "  frameborder = " no "  border = " 0 "  marginwidth = " 0 "  
7       marginheight = " 0 "  scrolling = " no "  allowtransparency = " yes "  height = " 35 "  width = " 102 " ></ iframe >  
8        < a href = " javascript:void(0); "  onclick = " refreshCode(); " > 看不清，换一张 </ a >  
9       < br >  
10       < span id = " codeImg " >< img border = 0  src = " randomCode " ></ span >
11       < a href = " javascript:void(0); "  onclick = " reloadCode() " > 看不清，再换一张 </ a >

1  function $(id){ 
2       return  document.getElementById(id); 
3  } 
4   
5   /** 刷新iframe* */  
6  function refreshCode(){ 
7      window.frames[ " codeFrame " ].location.reload(); 
8  } 
9  
10   /** 替换图片* */
11  function reloadCode(){
12      $( " codeImg " ).innerHTML  =   " <img border=0 src='randomCode'> " ;
13  }