connectionprovider.java

自己整理的一些java工具类包括文件处理

package cn.com.pubinfo.dsfactory;

/**
 * Title:
 * Description:
 * Copyright:    Copyright (c) 2002
 * Company:
 * @author
 * @version 1.0
 */


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

public class ConnectionProvider {
   private Connection con;
   private Vector connectionPool = new Vector();
   private int count;
   private String classDriver,url,user,password;
   private int min,max,addCount;
/**
 * 构造 一个连接提供者，
 * @param classDriver 驱动源
 * @param url 数据库的JDBC URL
 * @param user 用户名
 * @param password 用户口令
 * @param min 最小连接数
 * @param max 最大连接数
 * @param addCount 每次新创建的个数。
 */
    ConnectionProvider(String classDriver,String url,String user,String password,int min,int addCount,int max)throws SQLException{
       this.classDriver = classDriver;
       this.url = url;
       this.user = user;
       this.password = password;
       this.min = min;
       this.max = max;
       this.addCount = addCount;
       Connection tempCon =null;
       try{
           for(int i=0;i<min;i++){
             tempCon=this.createCon(classDriver,url,user,password);
             connectionPool.addElement(tempCon);
           }
           count = min;
      }catch(Exception e){
           throw new SQLException();
      }
  }

   /**
 * 从连接池获取可用连接.可以指定客户程序能够等待的最长时间
 * 参见前一个getConnection()方法.
 *
 * @param timeout 以毫秒计的等待时间限制
 */
 public synchronized Connection getConnection(long timeout) {
     long startTime = System.currentTimeMillis();
     while ((con = getConnection()) == null) {
       try {
       wait(timeout);
       }
       catch (InterruptedException e) {}
     if ((System.currentTimeMillis() - startTime) >= timeout) {
     // wait()返回的原因是超时
       return null;
       }
     }
     return con;
 }
   public synchronized Connection getConnection(){
      if(connectionPool.size()>0){
          con = (Connection)connectionPool.firstElement() ;
          connectionPool.removeElementAt(0);
          try{
            if(con.isClosed()){
              con = getConnection();
            }
          }catch(Exception e){e.printStackTrace();
             return null ;
          }
          return con;
      }else if(count < max){
         try{
             for(int i=0;i<addCount;i++){
                con=this.createCon(classDriver,url,user,password);
                connectionPool.addElement(con);
             }
              count+=addCount;
         }catch(Exception e){
            e.printStackTrace();
         }
         con = getConnection();
          return con;

      }
      return null ;
   }
   public synchronized void freeConnection(Connection con){
     connectionPool.addElement(con);
   }
   private Connection createCon(String driver,String url,String user,String pwd)throws SQLException{
       Connection tempCon=null;
       String className=driver;
         try{
          Class.forName(className).newInstance();
         }
         catch(Exception e)
         {
           throw new SQLException("not class");
         }
         try {

           // setConnectionProvider((ConnectionProvider)conClass.newInstance());
            tempCon=DriverManager.getConnection(url,user,pwd);

            }
          catch(Exception e) {
               throw new SQLException("can not create a connection");

          }
      return tempCon;
   }
   public synchronized void destroy(){
       Enumeration allConnections = connectionPool.elements();
       while (allConnections.hasMoreElements()) {
        con = (Connection) allConnections.nextElement();
         try {
            con.close();

         } catch (SQLException e) {
               e.printStackTrace();
         }
       }
        connectionPool.removeAllElements();
   }
}