在jsp页面上用EL表达式获取验证码类里存的验证码的值
HttpSession session = request.getSession(true);
session.setAttribute("rand", sRand);
JSP页面上${rand},第一次加载能看到验证码,但得不到值,第二次刷新,才能看到第一次验证码的值
EL表达式每次只能取到上一次验证码的值?请问怎么解决这个问题
HttpSession session = request.getSession(true);
session.setAttribute("rand", sRand);
JSP页面上${rand},第一次加载能看到验证码,但得不到值,第二次刷新,才能看到第一次验证码的值
EL表达式每次只能取到上一次验证码的值?请问怎么解决这个问题
解决方案 »
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session是有生命周期的
要注意这个
服务器编译时就执行了一次?怎么改呢
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
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;public class GetImg extends HttpServlet {
private Font mFont = new Font("Times New Roman", Font.PLAIN, 17); /**
* 产生随机颜色
* @param fc
* @param bc
* @return
*/
private Color getRandColor(int fc, int bc) {
Random random = new Random();
if (fc > 255)
fc = 255;
if (bc > 255)
bc = 255;
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//禁止客户端浏览器缓存
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
// 表明生成的响应是图片
response.setContentType("image/jpeg"); //在内存缓冲区中创建图片
int width = 90, height = 20;
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200, 250));
g.fillRect(1, 1, width - 1, height - 1);
g.setColor(new Color(102, 102, 102));
g.drawRect(0, 0, width - 1, height - 1);
g.setFont(mFont); g.setColor(getRandColor(160, 200)); // 画随机线
for (int i = 0; i < 155; i++) {
int x = random.nextInt(width - 1);
int y = random.nextInt(height - 1);
int xl = random.nextInt(6) + 1;
int yl = random.nextInt(12) + 1;
g.drawLine(x, y, x + xl, y + yl);
} // 从另一方向画随机线
for (int i = 0; i < 70; i++) {
int x = random.nextInt(width - 1);
int y = random.nextInt(height - 1);
int xl = random.nextInt(12) + 1;
int yl = random.nextInt(6) + 1;
g.drawLine(x, y, x - xl, y - yl);
}
// 生成随机数,并将随机数字转换为字母
String sRand = "";
for (int i = 0; i < 4; i++) {
int itmp = random.nextInt(26) + 65;
char ctmp = (char) itmp;
sRand += String.valueOf(ctmp);
g.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));
g.drawString(String.valueOf(ctmp), 20 * i + 10, 18);
}
//将验证码保存至Session
HttpSession session = request.getSession(true);
session.setAttribute("rand", sRand);
g.dispose();
//输出到客户端
ImageIO.write(image, "JPEG", response.getOutputStream());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}}一下是页面
<form action="register.do" method="post">
<TABLE width=60% cellpadding=0 align="center">
<TR>
<TD><a href="index.jsp">xxx论坛</a>>>注册</TD>
</TR>
<TR>
<TD>
<TABLE rules=rows border=0 cellspacing=1 cellpadding=4 class="bg" width="100%" height="100%" > <!--嵌套表格 -->
<TR>
<TD colspan=2><B>注册</B></TD>
</TR>
<TR style="background:#FFFFCC;">
<TD style="color:#99CC00;" colspan=2><B>必填</B></TD>
</TR>
<TR>
<TD style="color:#000000;" colspan=2 align="center"><span id="inputinfo">注册信息</span></TD>
</TR>
<TR class="tr">
<TD width=200x ><B>用户名</B></TD>
<TD><input type="text" name="username" id="username"/>
<span id="usernametx"></span>
</TD>
</TR>
<TR class="tr">
<TD><B>密码</B></TD>
<TD><input type="password" name="password" id="pwd1">
<span id="pwd1tx" ></span>
</TD>
</TR>
<TR class="tr">
<TD><B>确认密码</B></TD>
<TD>
<input type="password" style="float:left;" id="pwd2">
<span id="pwd2tx"></span>
</TD>
</TR>
<TR class="tr">
<TD><B>性别</B></TD>
<TD>
<input type="radio" name="userSex" value="1" checked="checked">男
<input type="radio" name="userSex" value="2">女
</TD>
</TR>
<TR class="tr">
<TD><B>Email</B></TD>
<TD>
<input type="text" style="float:left"" name="userEmail" id="userEmail" value="@">
<span id="emailtx"></span>
</TD>
</TR>
<TR class="tr">
<TD><B>验证码:<img src="GetImg" alt="图形验证码" onclick="this.src='GetImg?'+new Date().getTime()"; ></img></B></TD>
<TD><input style="float:left" type="text" id="ValidType" name="ValidType">
<input type="text" value="${sessionScope.rand}">
<span id="imgtx"></span>
</TD>
</TR>
</TABLE>
</TD>
</TR>
<TR>
<TD>
<TABLE cellspacing=1 border=0 class="bg" width="100%" height="100%">
<TR class="tr">
<TD height=30px align="center" >
<input class="btn" type="submit" value="注 册" disabled="disabled" id="sub">
<input class="btn" type="reset" value="重 置">
</TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE>
</form>
</body>