代码是检查用户的大学输入是否已存在于数据库中。如果是，则提交输入并转到下一页;如果没有，则向用户发送警报消息并保持在同一页面上，即choose_university.jsp。 checkUniversity.jsp用于连接数据库并进行检查。但是代码没有这样做。我已经花了几个小时，仍然无法弄明白。谁能告诉我它有什么问题，并告诉我如何解决它？它将在明天到期。请帮我。
choose_university.jsp如下：
<%@page import="java.util.*"%>
<html>
<head><title>Provide degrees - choose university</title>
<script type="text/javascript">
function validate() {
var xmlHttp;
xmlHttp = new XMLHttpRequest();
if (xmlHttp == null) {
alert("Your browser does not support AJAX!");
return;
}
var u = document.getElementById("university").value;
var url = "checkUniversity.jsp";
url = url + "?university=" + u;
xmlHttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 ) {
document.getElementById("university").innerHTML = xmlhttp.responseText;
}
}
alert("yea we got 55555");
xmlHttp.open("GET", url, true);
xmlHttp.send(null);
}
function GetXmlHttpObject() {
var xmlHttp = null;
try {
// Firefox, Opera 8.0+, Safari
xmlHttp = new XMLHttpRequest();
} catch (e) {
// Internet Explorer
try {
xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
}
return xmlHtp;
}
</script>
</head>
<body>
<br> If you can't find your university, please provide it in the following and hit submit <br>
<form method="post" action="Provide_degrees_Choose_discipline.jsp" onsubmit = "return validate()">
<p>To manually add your university </p> <br>
<p> name of university: <input type = "text" id="university" name = "university" /> </p><br>
<input type="submit" name = "submit" value="submit" />
</form>
</body>
</html>
/* checkUniversity.jsp */
<% response.setContentType("text/xml") ; %>
<%@ page import="javax.sql.*"%>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%>
<%@ page import="model.ApplicationModel" %>
<html>
<head><title>check university</title>
</head>
<body>
<%
System.out.println("heyheyhey");
String u = request.getParameter("university") ;
Class.forName("org.postgresql.Driver");
// Open a connection to the database using DriverManager
conn = DriverManager.getConnection(
"jdbc:postgresql://localhost:5432/access?" +
"user=postgres&password=neshorange");
// Create the statement
Statement statement = conn.createStatement();
// Use the created statement to SELECT
// the student attributes FROM the Student table.
rs = statement.executeQuery("SELECT count(*) as c FROM universities WHERE university=\'"+ u +"\';");
if (rs.next()){
if ( rs.getInt("c") > 0) {
response.write("false");
} else {
response.write("true");
}
}
response.write("true");
%>
</body>
</html>
尝试摆脱onSubmit中的“返回”，然后重试。还要安装firebug或其他检查员（如果你还没有），这样你就可以看到javascript并请求错误。
这些天也没有必要经历这样的所有ajax。看看像jQuery或Mootools这样的javascript库。他们可以将你的js代码转换成几行。
试试这个
function validate()
{
var u = document.getElementById("university").value;
$.post('checkUniversity.jsp?university=' + u, function(data) {
if(data==true) return true;
else
{
alert("user doesnot exists ")
return false;
}
});
}
如果用户来自checkUniversity.jsp，则返回true