package stumng;

import java.sql.*;
import java.util.*;

/*連接池類.能夠根據要求創建新連接,直到最大連接數為止.*/
public class DBConnPool {
       //實際使用中的連接數
       private int inUse=0;
       //空閑連接
       private Vector connections = new Vector();
       //連接池名
       private String poolname;
       //數據庫標識
       private String dbid;
       //驅動程序名
       private String drivername;
       //數據庫賬號
       private String username;
       //數據庫密碼
       private String passwd;
       //最大連接數
       private int maxconn;

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

       /*將連接返回給連接池*/
       public synchronized void releaseConnection(Connection con) {
               // 將指定連接加入到向量末尾
               connections.addElement(con);
               //連接數減一
               inUse--;
       }

       /*從連接池得到一個連接*/
       public synchronized Connection getConnection() {
               Connection con = null;
               if (connections.size() > 0) {
                       // 獲取連接列表中獲得第一個連接
                       con = (Connection) connections.elementAt(0);
                       connections.removeElementAt(0);
                       //如果此連接已關閉，則繼續獲取
        try {
           if (con.isClosed())
              con = getConnection();
        }
        catch (Exception ex) {
           ex.printStackTrace();
        }
               }
               //如果實際使用的連接小于最大連接數，就新創建一個連接
               else if (maxconn == 0 || inUse < maxconn) {
                       con = newConnection();
               }
               if (con != null) {
                       //連接數增一
                       inUse++;
               }
               //返回一個連接
               return con;
       }

       /*創建新的連接*/
       private Connection newConnection() {
               Connection con = null;
               try {
                       //加載驅動程序
                       Class.forName(drivername);
                       //建立連接
                       con = DriverManager.getConnection(dbid, username, passwd);
               }
               catch (Exception e) {
                       e.printStackTrace();
                       return null;
               }
               //返回該連接
               return con;
       }

       /*關閉所有連接*/
       public synchronized void closeConn() {
               Enumeration allConnections = connections.elements();
               while (allConnections.hasMoreElements()) {
                       Connection con = (Connection) allConnections.nextElement();
                       try {
                               con.close();
                       }
                       catch (SQLException e) {
                               e.printStackTrace();
                       }
               }
               connections.removeAllElements();
       }
}