tomcat無法連接連接Postgresql~求助

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kaisite2004:
<%@ page import="java.sql.*" %>

<h2>Location</h2>
<table border=1>
<tr>
<th>id</th>
<th>lat</th>
<th>lng</th>
<th>time</th>
</tr>
<%
String jdbcDriverName="org.postgresql.Driver";
Driver driver = (Driver) Class.forName(jdbcDriverName).newInstance();
DriverManager.registerDriver(driver);
Connection dbcon = DriverManager.getConnection("jdbc:postgresql:postgres","postgres","123456");
Statement st = dbcon.createStatement();
ResultSet rt = st.executeQuery("select * from test");
while(rt.next())
{
%>

<tr>
<td><%=rt.getString("id")%></td><td><%=rt.getString("lat")%></td><td><%=rt.getString("lng")%></td><td><%=rt.getString("time")%></td>
</tr>
<%
}
%>

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
<style type="text/css">
html { height: 50% }

#map_canvas { height: 100px;width:100px; }
</style>
<script type="text/javascript"
src="https://maps.googleapis.com/maps/api/js?v=3.exp&sensor=false">
</script>
<script type="text/javascript">
function initialize() {
var mapOptions = {
center: new google.maps.LatLng(<%=rt.getString("lat")%>, <%=rt.getString("lng")%>),
zoom: 8,
mapTypeId: google.maps.MapTypeId.ROADMAP
};
var map = new google.maps.Map(document.getElementById("map_canvas"),mapOptions);

         marker = new google.maps.Marker
({
         position: new google.maps.LatLng(<%=rt.getString("lat")%>, <%=rt.getString("lng")%>),
map: map
});

}
</script>
</head>
<body onLoad="initialize()">

<div id="map_canvas" style="width:100%; height:100%"></div>

</body>
</html>
<%
rt.close();
st.close();
dbcon.close();
%>

錯誤信息
HTTP Status 500 - An exception occurred processing JSP page /test2.jsp at line 44

type Exception report

message An exception occurred processing JSP page /test2.jsp at line 44

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /test2.jsp at line 44

41: <script type="text/javascript">
42: function initialize() {
43: var mapOptions = {
44: center: new google.maps.LatLng(<%=rt.getString("lat")%>, <%=rt.getString("lng")%>),
45: zoom: 8,
46: mapTypeId: google.maps.MapTypeId.ROADMAP
47: };

Stacktrace:
   org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
   org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:455)
   org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
   org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
root cause

javax.servlet.ServletException: org.postgresql.util.PSQLException: 查詢結果指標位置不正確，您也許需要呼叫 ResultSet 的 next() 方法。
   org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:912)
   org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:841)
   org.apache.jsp.test2_jsp._jspService(test2_jsp.java:157)
   org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
   org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
   org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
   org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
root cause

org.postgresql.util.PSQLException: 查詢結果指標位置不正確，您也許需要呼叫 ResultSet 的 next() 方法。
   org.postgresql.jdbc2.AbstractJdbc2ResultSet.checkResultSet(AbstractJdbc2ResultSet.java:2860)
   org.postgresql.jdbc2.AbstractJdbc2ResultSet.getString(AbstractJdbc2ResultSet.java:1955)
   org.postgresql.jdbc2.AbstractJdbc2ResultSet.getString(AbstractJdbc2ResultSet.java:2567)
   org.apache.jsp.test2_jsp._jspService(test2_jsp.java:117)
   org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
   org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
   org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
   org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.42 logs.

Apache Tomcat/7.0.42

請問查詢結果指標位置不正確，您也許需要呼叫 ResultSet 的 next() 方法。
是位什麼?

h2owater:
你好!

在你的程式碼
line 18 while(rt.next())

已經在 line 26 跑完了, rt 已經指向null record

在 line 44 再以 rt.getString("lat") 語法便會 throw exception

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