JSP生成验证码

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image.jsp

<%@pagelanguage="java"import="java.util.*"pageEncoding="gb2312"%>

<%@pagecontentType="image/jpeg"import="java.awt.*,

java.awt.image.*,java.util.*,javax.imageio.*"%>

<%!

    //随机颜色

    ColorgetRandColor(intfc,intbc)

{

        Randomrandom=newRandom();

        if(fc>255)fc=255;

        if(bc>255)bc=255;

        intr=fc+random.nextInt(bc-fc);

        intg=fc+random.nextInt(bc-fc);

        intb=fc+random.nextInt(bc-fc);

        returnnewColor(r,g,b);

}

%>

<%

    out.clear();

    //设置页面不缓存

    response.setHeader("Pragma","No-cache");

    response.setHeader("Cache-Control","no-cache");

    response.setDateHeader("Expires",0);

    //定义图片的长度和高度

    intwidth=60,height=20;

    //在内存中创建图像

    BufferedImageimage=newBufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

    Graphicsg=image.getGraphics();

    //随机类

    Randomrandom=newRandom();

    //设置背景

    g.setColor(getRandColor(200,250));

    g.fillRect(0,0,width,height);

    //字体定义

    g.setFont(newFont("Times New Roman",Font.PLAIN,18));

    g.setColor(getRandColor(160,200));

    //用线条画背景

    for(inti=0;i<155;i++)

{

        intx=random.nextInt(width);

        inty=random.nextInt(height);

        intxl=random.nextInt(12);

        intyl=random.nextInt(12);

        g.drawLine(x,y,x+xl,y+yl);

}

    //生成验证码随机数

    StringsRand="";

    for(inti=0;i<4;i++){

        Stringrand=String.valueOf(random.nextInt(10));

        sRand+=rand;

        g.setColor(newColor(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));

        g.drawString(rand,13*i+6,16);

}

    //将认证码存入SESSION

    session.setAttribute("code",sRand);

    g.dispose();

    //输出图像

    ImageIO.write(image,"JPEG",response.getOutputStream());

%>

login.jsp

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<%@pagecontentType="text/html; charset=gb2312"language="java"import="java.sql.*"errorPage=""%>
<html>
<head>
<title>登录页面</title>
<scriptlanguage="javascript">
functionloadimage(){
document.getElementById("randImage").src="image.jsp?"+Math.random();
}
</script>
</head>
 
<body>
<formaction="check.jsp"method="post"name="loginForm">
<tdwidth="118"height="22"  valign="middle"align="center"><inputtype="text"name="code"size="15"></td>
<tdwidth="138"align="center"><ahref="javascript:loadimage();"><imgname="randImage"id="randImage"src="image.jsp"width="60"height="20"  valign="middle"border="1"></a>点击图片刷新
  <inputtype="submit"name="login"value="提交"></td>
</form>
</body>
</html>
check.jsp

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<%@pagecontentType="text/html; charset=gb2312"language="java"%>
<%
    Stringrand=(String)session.getAttribute("code");
    Stringinput=request.getParameter("code");
    if(rand.equals(input)){
      out.print("<script>alert('验证成功');</script>");
    }else{
      out.print("<script>alert('验证失败');location.href='login.jsp';</script>");
    }
%>