javabeans连接mysql但是调用的时候rs却是为空,麻烦高手帮忙看下,我的javabeans如下:package com.search;import java.sql.*;public class searchgov
{
private String DbName = "";
private String pass = "";
private String url = "";
private Connection con = null;
private Statement stmt = null;
private ResultSet rs = null;public searchgov()
{
}public void setDbName (String name)
{
this.DbName = name;
}
public void setPass (String pass)
{
this.pass = pass;
}public void BulidCon()
{
try
{
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
url ="jdbc:mysql://localhost/"+DbName+"?user=root&password="+pass+"&useUnicode=true&characterEncoding=utf8";
con= DriverManager.getConnection(url);
stmt=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
}
catch (Exception e)
{
}
}public ResultSet selectLog(String sql)
{
try
{
BulidCon();
rs = stmt.executeQuery(sql);
}
catch(Exception e)
{
System.out.println(e.toString());
}
return rs;
}public void updateLog(String sql)
{
try
{
BulidCon();
stmt.executeUpdate(sql);
}
catch (Exception e)
{
}
}public void close()
{
try
{
con.close();
stmt.close();
}
catch (SQLException e)
{
}
}}我调用的代码:
<%--
Document : test1
Created on : 2008-6-9, 14:06:24
Author : admin
--%><%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<%@ page import = "com.search.searchgov" %>
<%@ page import = "java.sql.*" %>
<%@ page import = "java.lang.String" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<jsp:useBean id="searche" scope="page" class="com.search.searchgov" /> <%
searche.setDbName("test");
searche.setPass("123456");
String sql="select * from public_gov order by crtime desc";
ResultSet rs=searche.selectLog(sql);
out.println(rs);
%>
</body>
</html>
{
private String DbName = "";
private String pass = "";
private String url = "";
private Connection con = null;
private Statement stmt = null;
private ResultSet rs = null;public searchgov()
{
}public void setDbName (String name)
{
this.DbName = name;
}
public void setPass (String pass)
{
this.pass = pass;
}public void BulidCon()
{
try
{
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
url ="jdbc:mysql://localhost/"+DbName+"?user=root&password="+pass+"&useUnicode=true&characterEncoding=utf8";
con= DriverManager.getConnection(url);
stmt=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
}
catch (Exception e)
{
}
}public ResultSet selectLog(String sql)
{
try
{
BulidCon();
rs = stmt.executeQuery(sql);
}
catch(Exception e)
{
System.out.println(e.toString());
}
return rs;
}public void updateLog(String sql)
{
try
{
BulidCon();
stmt.executeUpdate(sql);
}
catch (Exception e)
{
}
}public void close()
{
try
{
con.close();
stmt.close();
}
catch (SQLException e)
{
}
}}我调用的代码:
<%--
Document : test1
Created on : 2008-6-9, 14:06:24
Author : admin
--%><%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<%@ page import = "com.search.searchgov" %>
<%@ page import = "java.sql.*" %>
<%@ page import = "java.lang.String" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<jsp:useBean id="searche" scope="page" class="com.search.searchgov" /> <%
searche.setDbName("test");
searche.setPass("123456");
String sql="select * from public_gov order by crtime desc";
ResultSet rs=searche.selectLog(sql);
out.println(rs);
%>
</body>
</html>
我试了一下,如果报空指针异常基本上就是数据库的名字,或者密码不对,也可能是SQL语句~把这些都写对了运行是没问题的
url ="jdbc:mysql://localhost/"+DbName+"?user=root&password="+pass+"&useUnicode=true&characterEncoding=utf8";
con= DriverManager.getConnection(url);
stmt=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);打印下con是不是为null
{
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
url ="jdbc:mysql://localhost/"+DbName+"?user=root&password="+pass+"&useUnicode=true&characterEncoding=utf8";
con= DriverManager.getConnection(url);
stmt=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
}
catch (Exception e)
{
System.out.println(e.toString());
}把这里改成这样你就明白了