这是我第一次尝试在两个JSP页面之间交换值,index.jsp页面有登录形式,login.jsp页面将验证此登录,如果登录失败,它将重定向到索引。 jsp以及一个名为valid的参数,值为0,如果成功,则该值为1.
的index.jsp
<%@page import="javax.enterprise.inject.spi.Bean"%>
<%@page import="myDatabase.Login"%> //this is class that I created
<%@page import="myDatabase.JavaDB"%> //this is a class that I created
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link rel="stylesheet" type="text/css" href="indexCSS.css" />
<title>Chat</title>
</head>
<body>
<jsp:include page="login.jsp">
<jsp:param name="valid" value="1"/>
</jsp:include>
<% String valid = request.getParameter("valid");%>
<div class="mainPage">
<div id="header">
<div id="pageTitle">
Chat
</div>
</div>
<div id="loginBox">
<form name="login" action="login.jsp" method="POST">
<div id="loginItems">
<div id="loginTitle">
Log in
</div>
<hr style="color:green;">
<div style="margin-top:17px; overflow:hidden;">
<label for="id">
ID
</label>
<span id="idError" class="error">
<% if(valid.equals("0")) { %>is not valid<% } %>
</span>
<br>
<input class="inputText" type="text" name="id" value="" maxlength="10" autocomplete="off"/>
</div>
<div style="margin-top:17px; overflow:hidden;">
<label for="password">
Password
</label>
<span id="passwordError" class="error">
</span>
<br>
<input class="inputText" type="password" name="password" value="" maxlength="32" autocomplete="off"/>
</div>
<div style="margin-top:17px; overflow:hidden;">
<div>
Forgot your Password?
</div>
</div>
<div style="margin-top:17px; position:relative; overflow:hidden">
<input class="inputButton" type="submit" value="Log in" name="loginButton" />
</div>
</div>
</form>
</div>
</div>
</body>
</html>
这是login.jsp
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<jsp:useBean id="loginBean" scope="session" class="myDatabase.Login" />
<jsp:setProperty name="loginBean" property="id" />
<jsp:setProperty name="loginBean" property="password" />
<%
JavaDB myJavaDB=new JavaDB();
myJavaDB.Connect("IULChat","iul","iul");
if(myJavaDB.isConnected()==true){
//response.sendRedirect("index.jsp?a=2");
Login myLogin = new Login(loginBean.getId(),loginBean.getPassword());
myLogin.setConn(myJavaDB.getMyConnection());
myLogin.login(); loginBean.setId(0); loginBean.setPassword("");
if(myLogin.isValid()==true)
{
response.sendRedirect("index.jsp?valid=1");
}
else
{
response.sendRedirect("index.jsp?valid=0");
}
}
else
out.println("no");
%>
</body>
</html>
当我运行项目时,我收到此错误。
type Exception report
message
descriptionThe server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: java.lang.NullPointerException
root cause
java.lang.NullPointerException
note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 3.1.2 logs.
如果我删除本节中的java代码
,则此错误消失 <span id="idError" class="error">
<% if(valid.equals("0")) { %>is not valid<% } %>
</span>
答案 0 :(得分:1)
Redirect
将被视为全新请求,因此您将使用以前的请求参数。如果您希望将请求参数保留为下一页,则可能需要考虑使用forward
。
答案 1 :(得分:1)
页面可能抛出NullPointerException,因为'valid'的值为null。 始终使用格式
进行字符串比较<literal>.equals(<variable>)
尝试使用以下更新的代码行:
<span id="idError" class="error">
<% if("0".equals(valid)) { %>is not valid<% } %>
</span>