关于关闭数据库的问题？

Question

看看rst，conn变量的作用域，要定义在try块外面

Answer 1

package DBean;
import java.util.*;
import java.sql.*;public class sample{    private java.sql.Connection conn = null;
    private java.sql.Statement  stmt = null;
    private java.sql.ResultSet  rset = null;
     
   /*  这里是开启连接的方法  */
    public void connectToDB(){
          
           try{               Class.ForName("....");
               conn = DriverManager("..","..","..");
   
           }catch(java.lang.NotClassFoundException ex){
               System.err.print("ConnectoToDB() err:" + ex.toString());
           }       
        }
   
    /*  关闭连接的方法*/
    public void disconnectToDB() thorws 
      java.sql.SQLException{
              
           if(rset!=null)
             {
                 rset.close();
                 rset = null;  
              }   
           
           if(stmt!=null){
                 stmt.close();
                 stmt = null;  
              }           if(conn!=null)
             {
                 conn.close();
                 conn = null;  
              } 
        }
}

Answer 2

javabean代码如下：package online;
import java.sql.*;
public class onlineconn1
{
  String sDBDriver = "sun.jdbc.odbc.JdbcOdbcDriver";
  String sConnStr = "jdbc:odbc:online";
  Connection conn = null;
  ResultSet rs = null;
  public onlineconn1() 
  {
    try {
           Class.forName(sDBDriver);
         }
    catch(java.lang.ClassNotFoundException e)
         {
           System.err.println("onlineconn(): " + e.getMessage());
         }
  }
  public ResultSet executeQuery(String sql)
  {
     rs = null;
     try {
            conn = DriverManager.getConnection(sConnStr);
            Statement stmt = conn.createStatement();
            rs = stmt.executeQuery(sql);
          }
     catch(SQLException ex)
         {
            System.err.println("aq.executeQuery: " + ex.getMessage());
          }
     return rs;
  }
  public void executeUpdate(String sql)
  {
     try {
            conn = DriverManager.getConnection(sConnStr);
            Statement stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
            stmt.executeUpdate(sql);
          }
     catch(SQLException ex)
         {
            System.err.println("aq.executeUpdate: " + ex.getMessage());
          }
  }
}页面代码如下：
<%@  page  contentType="text/html;charset=ISO8859_1"%>
<%@ page language="java"%>
<%@ page import="java.*"%>
<jsp:useBean id="workM" scope="page" class="online.onlineconn1" />
<jsp:useBean id="workc" scope="page" class="online.ISOtoGb2312" />
<%
String errorMessage="",
           sex=request.getParameter("sex"),
   num=request.getParameter("num").trim(),
   emailh=request.getParameter("emailh").trim(),
   emaile=request.getParameter("emaile").trim(),
   sub1=request.getParameter("sub1");
java.util.Date now1 = new java.util.Date(); 
java.sql.Date now = new java.sql.Date(now1.getTime()); 
if (null == sex || "".equals(sex.trim())) errorMessage +="[请选择学生性别！]<br>";
if (num.length()==0) errorMessage +="[请输入学生学号！]<br>";
if (emailh.length()==0) errorMessage +="[请输入邮箱名称！]<br>";
if (emaile.length()==0) errorMessage +="[请输入邮箱域名！]<br>";
if ("0".equals(sub1.trim())) errorMessage +="[请选择学习科目！]<br>";
if (errorMessage !="") {
%>
<jsp:forward page="stuerror.jsp">
  <jsp:param name="errorMesage" value='<%=workc.convert(errorMessage)%>' />
</jsp:forward>
<%
}
String strSQL;
strSQL="INSERT INTO student(name,sex,brithyear,brithmonth,brithday,grade,xy,zy,lx,num,mkey,emailh,emaile,sub1,sub2,date,ip) Values('"+workc.convert(request.getParameter("name"))+"','"+workc.convert(request.getParameter("sex"))+"','"+workc.convert(request.getParameter("brithyear"))+"','"+workc.convert(request.getParameter("brithmonth"))+"','"+workc.convert(request.getParameter("brithday"))+"','"+workc.convert(request.getParameter("grade"))+"','"+workc.convert(request.getParameter("xy"))+"','"+workc.convert(request.getParameter("zy"))+"','"+workc.convert(request.getParameter("lx"))+"','"+workc.convert(request.getParameter("num"))+"','"+workc.convert(request.getParameter("mkey"))+"','"+workc.convert(request.getParameter("emailh"))+"','"+workc.convert(request.getParameter("emaile"))+"','"+workc.convert(request.getParameter("sub1"))+"','"+workc.convert(request.getParameter("sub2"))+"','"+now+"','"+workc.convert(request.getRemoteAddr())+"')";
workM.executeUpdate(strSQL);
%><title>=== 学生注册成功 ==</title>
<link rel="stylesheet" href="pub.css" type="text/css">
<body topmargin="70" bgcolor="#E8FFE8">
<center>
  <table width="400" border="1" cellspacing="1" cellpadding="1" bordercolor="#006633">
    <tr> 
      <td align="center" valign="middle" bgcolor="#009900" class="titlewhite" height="27">=== 
        恭喜！学生注册成功！===</td>
    </tr>
    <tr> 
      <td align="center" valign="middle" bgcolor="#FFFFFF" height="170" class="word">您已经注册成功，请牢记你的用户名和密码！</td>
    </tr>
    <tr> 
      <td align="right" valign="middle" bgcolor="#009900" height="20"><a href="index.htm" class="titlewhite">&lt;返回首页&gt;</a> 
        <a href="javascript:window.close()" class="titlewhite">&lt;关闭&gt;</a>&nbsp;&nbsp;</td>
    </tr>
  </table>
</center>
</body>

Answer 3

<jsp:useBean id="myBean" scope="page" class="DBean.sample"/>
<%
    try{
      myBean.connectToDB();
    }catch(java.sql.SQLException ex){
     out.print(ex.getMessage());      
    }finally{
     myBean.disconnectToDB();
    }%>能明白了吗? 
         
%>