JavaWeb 使用Session实现一次性验证码

 

表单

<form action="loginservlet" method="post">
  请输入验证码：<input type="text" name="code" />
  <img src="getcodeservlet" /><br />
  <button type="submit">提交</button>
</form>

载入页面时，会自动请求getcodeservlet，获取图片（验证码）。

 

 

 

getcodeservlet，产生验证码

 1 @webservlet("/getcodeservlet")
 2 public class getcodeservlet extends httpservlet {
 3     //验证码的宽、高
 4     private static int width=80;
 5     private static int height=25;
 6 
 7     //绘制背景
 8     private void drawbg(graphics g){
 9         //rgb
10         g.setcolor(new color(128, 128, 128));
11         //绘制矩形。x,y,wigth,height
12         g.fillrect(0,0,width,height);
13         //随机绘制100个干扰点
14         random random=new random();
15         for (int i=0;i<100;i++){
16             //产生(0,1）上的小数，*width|height，再取整也行
17             int x=random.nextint(width);
18             int y=random.nextint(height);
19             g.drawoval(x,y,1,1);
20 
21             //干扰点的颜色也可以随机，随机产生red，green，blue即可
22             //g.setcolor(new color(red,green,blue));
23         }
24     }
25 
26 
27     //绘制验证码
28     private void drawcode(graphics g,char[] code){
29         g.setcolor(color.black);
30         //字体、样式（多个时竖线分隔）、字号
31         g.setfont(new font("serif",font.italic|font.bold,18));
32         //在不同位置绘制验证码字符，参数：要绘制的string、横、纵坐标。+""是为了char转string。
33         g.drawstring(code[0]+"",1,17);
34         g.drawstring(code[1]+"",16,15);
35         g.drawstring(code[2]+"",31,18);
36         g.drawstring(code[3]+"",46,16);
37     }
38 
39     //随机产生4位验证码
40     private char[] getcode(){
41         string chars="0123456789qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnm";
42         char[] code=new char[4];
43         random random=new random();
44         for (int i=0;i<4;i++){
45             //[0,62)
46             int index= random.nextint(62);
47             code[i]=chars.charat(index);
48         }
49         return code;
50     }
51 
52 
53     protected void dopost(httpservletrequest request, httpservletresponse response) throws ioexception {
54         httpsession session = request.getsession();
55         servletoutputstream sos = response.getoutputstream();
56         response.setcontenttype("image/jpeg");
57 
58         //设置浏览器不缓存此图片
59         response.setheader("pragma","no-cache");
60         response.setheader("cache-control","no-cache");
61         response.setdateheader("expires",0);
62 
63         //创建内存图片
64         bufferedimage bufferedimage = new bufferedimage(width, height, type_int_rgb);
65         graphics g= bufferedimage.getgraphics();
66         char[] code=getcode();
67         //将验证码放到session域中。session对象要在提交响应之前获得
68         session.setattribute("code",new string(code));
69         drawbg(g);
70         drawcode(g,code);
71         g.dispose();
72 
73         //将图片输出到浏览器
74         bytearrayoutputstream baos = new bytearrayoutputstream();
75         imageio.write(bufferedimage,"jpeg",baos);
76         baos.writeto(sos);
77         baos.close();
78         sos.close();
79     }
80 
81     protected void doget(httpservletrequest request, httpservletresponse response) throws ioexception {
82         dopost(request,response);
83     }
84 }

 

 

 

loginservlet，处理表单

 1 @webservlet("/loginservlet")
 2 public class loginservlet extends httpservlet {
 3     protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 4         response.setcontenttype("text/html;charset=utf-8");
 5         httpsession session = request.getsession();
 6         string truecode= (string) session.getattribute("code");
 7         string code=request.getparameter("code");
 8 
 9         if (code.equals(truecode)){
10             response.getwriter().write("验证码正确");
11         }
12         else {
13             response.getwriter().write("验证码错误");
14         }
15     }
16 
17     protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
18         dopost(request,response);
19     }
20 }

 

上面的处理方式要区分验证码的大小写。

 

不区分大小写：

//先转换为全大写|全小写，再判断
        truecode=truecode.tolowercase();
        code=code.tolowercase();

        //truecode=truecode.touppercase();
        //code=truecode.touppercase();