为什么不会返回错误的提示框,比如用户名为空的

为什么不会返回错误的提示框,比如用户名为空的应该返回一个提示框才对呀,帮忙
<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<meta http-equiv="refresh" content="3;url=denglu.jsp">
<title>无标题文档</title>
<%
request.setCharacterEncoding("gb2312");
String url="jdbc:odbc:driver={Microsoft Access Driver (*.mdb)};DBQ=D:\\Tomcat4\\webapps\\ROOT\\web1\\web\\db1.mdb";
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection con=DriverManager.getConnection(url);
Statement st=con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
//ResultSet rs=st;
String errmsg="错误!";
boolean founderr=false;
String name=errmsg;
String userpassword=errmsg;
String reuserpassword=errmsg;if(request.getParameter("name").equals("")){
errmsg=errmsg+"用户名不能为空,";
founderr=true;
}else name=request.getParameter("name");if(request.getParameter("userpassword").equals("")){
errmsg=errmsg+"密码不能为空,";
founderr=true;
}else userpassword=request.getParameter("userpassword");if(request.getParameter("reuserpassword").equals("")){
errmsg=errmsg+"密码确认不能为空,";
founderr=true;
}else reuserpassword=request.getParameter("reuserpassword");if(!userpassword.equals(reuserpassword)){
errmsg=errmsg+"两次密码不同!";
founderr=true;
}
String funtion=request.getParameter("funtion");
String partment=request.getParameter("partment");
String sql="select * from user where name='"+name+"'";
ResultSet rs=st.executeQuery(sql);
if(rs.next()){
errmsg=errmsg+"用户名已被别人注册";
founderr=true;
}
elseif(founderr==false) {
String sql1="insert into user(name,password,partment,funtion)values('"+name+"','"+userpassword+"','"+partment+"','"+funtion+"')";
st.executeUpdate(sql1);
}
st.close();
con.close();
%>
</head>
<body>

</body>
</html>

解决方案 »

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if(request.getParameter("userpassword")==null||request.getParameter("reuserpassword").equals("")){
request.getParameter("name")的结果有可能是"",也有可能是null。所以楼上的答案是可行的
这个应该叫客户端js验证．．．请楼主参考一下我的代码
<%@ page import="com.personalerp.workflow.cookie.CookieManager" %>
<%@ page contentType="text/html; charset=utf-8" language="java" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>
<fmt:setBundle basename="login" var="login"/>
<html>
<head>
<link rel="stylesheet" href="../main.css" type="text/css">
<title>login</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script language="JavaScript" type="text/JavaScript">
        function checkLoginForm() {
            if (document.loginForm.username.value.length <= 0) {
                alert('Please enter Username');
                document.loginForm.username.focus();
                return false;
            }
            if (document.loginForm.password.value.length <= 0) {
                alert('Please enter Password');
                document.loginForm.password.focus();
                return false;
            }
            else {
                return true;
            }
        }
        function clearTextField() {
            document.loginForm.username.value = "";
            document.loginForm.password.value = "";
        }    </script>
<script language="JavaScript" type="text/JavaScript">

</script>
</head><body style="background:#EEEEEE">
<form name="loginForm" action="./login.do" method="post">
    <table width="100%" border="0">

        <tr>
            <td> </td>
            <td>
              <div align="center"><img src="images/perp_login.jpg" width="640" height="480">
              </div>

              <div id="Layer1" style="position:absolute; width:300px; height:182px; z-index:1; left: 415px; top: 298px;">

   <table width="379" border="0" align="center">
                <tr>
                    <td width="66"><font color="#FFFFFF">
                        <fmt:message key="username" bundle="${login}"/></font>
                    </td>
                  <td width="173"><input type="text" name="username" value="<%=CookieManager.getCookieUsername()%>">
                  </td>
                    <td width="28"> </td>
                    <td width="94"> </td>
                </tr>
                <tr>
                    <td><font color="#FFFFFF"><fmt:message key="password" bundle="${login}"/></font></td>
                    <td><input type="password" name="password"></td>
                    <td><input type="checkbox" name="rememberflag" value="1"></td>
                    <td><font color="#FFFFFF"><fmt:message key="remember" bundle="${login}"/></font></td>
                </tr>
                <tr>
                    <td> </td>
                    <td> </td>
                    <td> </td>
                    <td> </td>
                </tr>
                <tr>                    <td> </td>
                    <td><input type="submit" name="submit" value="<fmt:message key="submit" bundle="${login}"/>"
                               onClick="return checkLoginForm()">
                        <input type="button" name="reset" value="<fmt:message key="reset" bundle="${login}"/>"
                               onClick="clearTextField()"></td>
                    <td> </td>
                    <td> </td>
                </tr>
                <tr>
                    <td> </td>
                    <td><a href="../mail.jsp"><fmt:message key="forget" bundle="${login}"/></a></td>
                    <td> </td>
                    <td> </td>
                </tr>
            </table>
</form></body>
</html>
你可以做前端验证吗
这样还可以减轻服务器的
用javascript写
很简单的
如果用你的这个中方法也可以的
if(request.getParameter("username")==null||request.getParameter("username").equals(""))
<%
   out.println("<script language=\"JavaScript\">");
   out.println("");
   out.println("</script>");
%>
你的程序中虽然定了errmsg这个字段,但是你根本就没有让他显示,怎么能给你弹出提示框呢
同意   xinxideyilian(心细的依恋) ( )  !!!