JSP用连接池连数据库的问题

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--- JSP用连接池连数据库的问题 (http://www.webasp.net/article/27/26605.htm)
-- 作者:未知
-- 发布日期: 2005-09-20
 

各位高手麻烦帮我看下面这三个文件(一个jsp,两个.java),我在IE输入地址时,提示如下错误(代码应该没有错,不知是不是设置的问题),望高手指教,不胜感激:

D:\Program Files\Apache Group\Tomcat 4.1\work\Standalone\localhost\_\shopping\index_jsp.java:44: package mybean does not exist
      mybean.DBConnManager connManager = null;
            ^



An error occurred at line: 2 in the jsp file: /shopping/index.jsp

Generated servlet error:
D:\Program Files\Apache Group\Tomcat 4.1\work\Standalone\localhost\_\shopping\index_jsp.java:46: package mybean does not exist
        connManager = (mybean.DBConnManager) pageContext.getAttribute("connManager", PageContext.APPLICATION_SCOPE);
                             ^



An error occurred at line: 2 in the jsp file: /shopping/index.jsp

Generated servlet error:
D:\Program Files\Apache Group\Tomcat 4.1\work\Standalone\localhost\_\shopping\index_jsp.java:49: package mybean does not exist
            connManager = (mybean.DBConnManager) java.beans.Beans.instantiate(this.getClass().getClassLoader(), "mybean.DBConnManager");
                                 ^

//下面这两个是连接池,下面两个文件都放在一个mybean的包里.

package mybean;
import java.sql.*;
import java.util.*;

public class DBConnPool {
  //正在使用连接的数量
  private int using;
  //目前可用的连接数,即空闲连接
  private Vector connections=new Vector();
  //最大连接数
  private int maxconn;
  //连接池名
  private String poolname;
  //数据库标识
  private String dbid;
  //驱动程序名
  private String drivername;
  //数据库帐号
  private String username;
  //数据库密码
  private String passwd;

  public DBConnPool(String poolname,String dbid,String drivername,
                    String username,String passwd,int maxconn){
    this.poolname=poolname;
    this.drivername=drivername;
    this.dbid =dbid;
    this.username =username;
    this.passwd=passwd;
    this.maxconn=maxconn;
  }

  /*将空闲连接返回给连接池*/
  public synchronized void returnConnection(Connection conn){
    //将指定连接加到向量末尾
    connections.addElement(conn);
    //连接用户减一
    using--;
  }

  /*从连接池得到一个连接*/
  public synchronized Connection getConnection(){
    Connection conn = null; //Connection是一个类,
    //connections是一个向量,用于存储连接对象,它所存储是的所有空闲状态的可用连接
    if (connections.size() > 0) {

      //获取连接列表的第一个连接
      conn = (Connection) connections.elementAt(0);
      connections.removeElementAt(0);//获得一个连接,并将此连接从队列中删除.

      //如果此连接已关闭,刚继续获取,
      try {
        if (conn.isClosed())
          conn = getConnection();
      }
      catch (Exception e) {
        e.printStackTrace();
      }
    }
      //如果实际使用的连接数小于最大连接数即有可用连接),就新增加一个连接
    else if (maxconn == 0 || using < maxconn){
      //如此时无可用连接(maxconn == 0)且连接数又未达到上限(using < maxconn)),就创建一个新连接
        conn=newConnection();
      }
      //如果连接数已达到上限就返回空指针
      if (conn!=null){
        using++;
      }
    return conn;
  }

/*创建新的连接*/
  public Connection newConnection(){
    Connection conn=null;
    try{
      //加载驱动
      Class.forName(drivername);
      conn=DriverManager.getConnection(dbid,username,passwd);
    }catch(Exception e){
      e.printStackTrace();
      return null;
    }
    return conn;
  }

 /*关闭所有连接*/
 public synchronized void closeConn(){
   Enumeration allConnections=connections.elements();
   while (allConnections.hasMoreElements()){
     Connection conn=(Connection) allConnections.nextElement();
     try{
       conn.close();
     }catch(SQLException e){
       e.printStackTrace();
     }
   }
   connections.removeAllElements();
 }
}

package mybean;
import java.sql.*;
import java.util.*;

public class DBConnManager {
  //连接池名列表
  private Vector poolnames =new Vector();
  //驱动程序名列表
  private Vector drivernames=new Vector();
  //数据库标识列表
  private Vector dbids=new Vector();
  //用户名列表
  private Vector usernames=new Vector();
  //用户密码列表
  private Vector passwds=new Vector();
  //最大连接数列表
  private Vector maxconns=new Vector();
  //连接池队列
  private Hashtable connPools=new Hashtable();

  public DBConnManager() {
    //添加Access数据库的连接信息
    poolnames.addElement("access");
    drivernames.addElement("sun.jdbc.odbc.JdbcOdbcDriver");
    dbids.addElement("jdbc:odbc:shopping");
    usernames.addElement("");
    passwds.addElement("");
    maxconns.addElement("5");

    //添加SQL Server2000数据库的连接信息
    poolnames.addElement("sqlserver2000");
    drivernames.addElement("com.microsoft.jdbc.sqlserver.SQLServerDriver");
    dbids.addElement("jdbc:microsoft:sqlserver://localhost:1433;DatabserName=shopping");
    usernames.addElement("");
    passwds.addElement("");
    maxconns.addElement("5");

    //连接Mysql数据库信息
    poolnames.addElement("mysql");
    drivernames.addElement("org.gjt.mm.mysql.Driver");
    dbids.addElement("jdbc:mysql://localhost/shopping");
    usernames.addElement("");
    passwds.addElement("");
    maxconns.addElement("5");

    //连接Oracle8i/9i数据库
    poolnames.addElement("oracle");
    drivernames.addElement("oracle.jdbc.driver.OracleDriver");
    dbids.addElement("jdbc:oracle:thin:@localhost:1521:shopping");
    usernames.addElement("");
    passwds.addElement("");
    maxconns.addElement("5");


    //创建连接池
    createPools();
  }

  /*将连接返回给由指定的连接池*/
  public void returnConnection(String name,Connection conn){
    DBConnPool pool=(DBConnPool) connPools.get(name);
    if (pool!=null)
    {
      pool.returnConnection(conn);
    }
  }

  /*得到一个指定连接池中的连接*/
  public Connection getConnection(String name){
    DBConnPool pool=(DBConnPool) connPools.get(name);
    if (pool!=null)
    {
      return pool.getConnection();
    }
    return null;
  }

  /*关闭所有连接*/
  public synchronized void closeConns(){
    Enumeration allPools=connPools.elements();
    while (allPools.hasMoreElements()){
      DBConnPool pool=(DBConnPool) allPools.nextElement();
      pool.closeConn();
    }
  }

  /*创建连接池*/
  private void createPools(){
    for (int i=0;i<poolnames.size();i++)
    {
      String poolname=poolnames.elementAt(i).toString();
      String drivername=drivernames.elementAt(i).toString();
      String dbid=dbids.elementAt(i).toString();
      String username=usernames.elementAt(i).toString();
      String passwd=passwds.elementAt(i).toString();
      int maxconn=0;
      try{
        maxconn=Integer.parseInt(maxconns.elementAt(i).toString());
      }catch (NumberFormatException e){
        e.printStackTrace();
      }
      DBConnPool pool=new DBConnPool(poolname,drivername,dbid,username,
                                     passwd,maxconn);
      connPools.put(poolname,pool);
    }
  }
}


下面这个是主页面.JSP文件

<%@ page contentType="text/html; charset=GBK" %>
<%@ page import ="java.sql.*" %>
<jsp:useBean id="connManager" scope="application" class="mybean.DBConnManager" />
<html>
<head>
<title>
购物商城首页
</title>
</head>
<body bgcolor="#B0C4DE">
<center><h1>欢迎访问本购物商城</h1></center>
<%
//Connection connA=connManager.getConnection("access");
Connection connS=connManager.getConnection("sqlserver2000");
if (connS==null)
{
%>
  数据库正忙,请稍后再访问
<%
}
//Statement stmtA=connA.createStatement();
Statement stmtS=connS.createStatement();
%>

<%
String sql="select * from userinfo";
ResultSet rs=stmtS.executeQuery(sql);
while (rs.next())
{
%>
<tr>
<td><%=rs.getString("username")%></td>
<td><%=rs.getString("userpass")%></td>
</tr>
<%
}
rs.close();
stmtS.close();
connManager.returnConnection("sqlserver2000",connS);
%>

</body>
</html>



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