public ResultSet connect(){
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection conn=DriverManager.getConnection("jdbc:odbc:javaApp");
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery("USE fancy SELECT ID FORM KL_Province");
return rs;
}
catch(Exception fe)
{
}
return null;
}
}
有2个return
合为一个,再试试?
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection conn=DriverManager.getConnection("jdbc:odbc:javaApp");
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery("USE fancy SELECT ID FORM KL_Province");
return rs;
}
catch(Exception fe)
{
}
return null;
}
}
有2个return
合为一个,再试试?
<%@ page import="java.sql.*"%>
<html>
<head>
<title>
Jdbc
</title>
</head>
<jsp:useBean id="JdbcBeanId" scope="session" class="test.JdbcBean" />
<jsp:setProperty name="JdbcBeanId" property="*" />
<body>
<h1>
JBuilder Generated JSP
</h1>
<%
ResultSet rs=JdbcBeanId.connect();
while(rs.next())
{
out.println(rs.getObject(1)+"<br>");
}
%>
</body>
</html>
请确认一下
java.lang.NullPointerException表示null错误
ResultSet rs=JdbcBeanId.connect();
while(rs.next())
{
out.println("hello world!");
}
%> 引用的时候,应该先判断是否为null
//这里返回的rs==nullwhile(rs!=null && rs.next()){
out.println("hello world!");
}
//这里返回的rs==null如果rs为空,怎么才能让它不为空呢?
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection conn=DriverManager.getConnection("jdbc:odbc:javaApp");
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery("USE fancy SELECT ID FORM KL_Province");
return rs;
}
catch(Exception fe)
{
//在这里print异常,看看是什么问题。
System.out.println(fe.getMessage());
}
use fancy !!! sql语句中怎么会有这个啊,肯定是书上错了,我的理解对吗?