空置针异常
是你将jsp嵌入html是出现的错误 或者数据库中根本就信息
你这样试试看
或者 用 if(true) return 查一下 看空指针在什么地方出现的
<html>
<body>
<%@ page language="java" import="java.sql.*" %>
<jsp:useBean id="sqlbean" scope="session" class="database.QQsql" />
<table width="300" border="1" cellspacing="2">
<tr>
<td>
<div align="center">NAME</div>
</td>
<td>
<div align="center">PHONE</div>
</td>
</tr>
<%
String name,phone;
ResultSet RS = sqlbean.sqlQuery("SELECT * FROM test"); while ( RS.next() )
{
name=RS.getString("name");
phone=RS.getString("phone");
%>
<tr>
<td>
<div align="center"><%=name%></div>
</td>
<td>
<div align="center"><%=phone%></div>
</td>
</tr>
<%
}
RS.close();
%>
</table>
</body>
</html>
是你将jsp嵌入html是出现的错误 或者数据库中根本就信息
你这样试试看
或者 用 if(true) return 查一下 看空指针在什么地方出现的
<html>
<body>
<%@ page language="java" import="java.sql.*" %>
<jsp:useBean id="sqlbean" scope="session" class="database.QQsql" />
<table width="300" border="1" cellspacing="2">
<tr>
<td>
<div align="center">NAME</div>
</td>
<td>
<div align="center">PHONE</div>
</td>
</tr>
<%
String name,phone;
ResultSet RS = sqlbean.sqlQuery("SELECT * FROM test"); while ( RS.next() )
{
name=RS.getString("name");
phone=RS.getString("phone");
%>
<tr>
<td>
<div align="center"><%=name%></div>
</td>
<td>
<div align="center"><%=phone%></div>
</td>
</tr>
<%
}
RS.close();
%>
</table>
</body>
</html>
public ResultSet sqlQuery(String sql){
try{
DBDriver();
if(cn==null){
System.out.println("connection is null!");
}
cn=DriverManager.getConnection(cn_str);
Statement stmt=cn.createStatement();
rs=stmt.executeQuery(sql);
}
catch(SQLException e){
System.err.println("SQL.executeQuery:"+e.getMessage());
}
return rs;
}看看后台有没有打印connection is null!再在页面上判断一下RS是否为空:
<%
ResultSet RS = sqlbean.sqlQuery("SELECT * FROM test");
if(RS==null){
out.println("rs is null !!");
return;
}
%>