动手实现随机验证码

动手实现随机验证码

首先，来写一个画验证码图片的Java类：

packagecom.XiongYi.validationCode;

importjava.awt.Color;
importjava.awt.Font;
importjava.awt.Graphics;
importjava.awt.image.BufferedImage;
importjava.io.IOException;
importjava.io.OutputStream;
importjava.util.Random;

importjavax.imageio.ImageIO;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;

publicclassValidationCodeextendsHttpServlet...{

publicstaticStringgetValidationCodes(OutputStreamos)...{
charcodeTable[]=...{
'a','b','c','d','e','f','g','h','i','j','k','l',
'm','n','p','q','r','s','t','u','v','w','x','y','z',
'A','B','C','D','E','F','G','H','I','J','K','L',
'M','N','P','Q','R','S','T','U','V','W','X','Y','Z',
'1','2','3','4','5','6','7','8','9'
};//判断时大小写不区分，另外，没有使用'O'和'0'，也是怕混淆的麻烦

BufferedImageimage=newBufferedImage(60,20,
BufferedImage.TYPE_INT_RGB);
//生成60×20的RGB图片
Graphicsgraphic=image.getGraphics();
//背景色
graphic.setColor(newColor(0xDCDCDC));
graphic.fillRect(0,0,60,20);

charcodes[]=newchar[4];
//随机产生验证码
for(inti=0;i<=3;i++)...{
codes[i]=codeTable[(int)(codeTable.length*Math.random())];
}

//把字画上去
graphic.setColor(Color.BLACK);
graphic.setFont(newFont("Arial",Font.BOLD,16));
for(inti=0;i<=3;i++)...{
graphic.drawChars(codes,i,1,2+15*i,15+i);
//把codes[i]画到坐标为[10+5*i,15+i]的地方去
}

//15个干扰点
Randomrand=newRandom();
for(inti=0;i<15;i++)
graphic.drawOval(rand.nextInt(60),rand.nextInt(20),1,1);

//释放此图形的上下文并释放它所使用的所有系统资源
graphic.dispose();

try...{
ImageIO.write(image,"JPEG",os);
}catch(IOExceptione)...{
e.printStackTrace();
}

returnnewString(codes,0,codes.length);
}

publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException...{
doPost(request,response);
}

publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException...{
request.getSession().setAttribute("validationCodes",getValidationCodes(response.getOutputStream()));
}

}

 

然后，写一个Servlet将生成的图片写入页面：

 

packagecom.XiongYi.servlet;

importjava.io.IOException;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;

importcom.XiongYi.validationCode.ValidationCode;

publicclassValidationServletextendsHttpServlet...{

publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException...{
doPost(request,response);
}

publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException...{
Stringstr=ValidationCode.getValidationCodes(response.getOutputStream());
request.getSession().setAttribute("validationCodes",str);
}

}

 

接着，在login.jsp中加入如下表单：

<%...
Stringpath=request.getContextPath();
StringbasePath=request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<formaction="<%=basePath+"servlet/LoginServlet"%>">
<imgsrc="<%=basePath+"servlet/ValidationServlet"%>"/>
<br>
<inputtype="text"name="codes"/>
<inputtype="submit"/>
</form>

 

再写进行后台判断的Servlet：

packagecom.XiongYi.servlet;

importjava.io.IOException;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;

publicclassLoginServletextendsHttpServlet...{
publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException...{
doPost(request,response);
}
publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException...{

if(request.getSession().getAttribute("validationCodes").toString().toLowerCase()
.equals(request.getParameter("codes").toString().toLowerCase()))
response.getOutputStream().println("Right!");
else
response.getOutputStream().println("Wrong!");

}

}