package connection;
import java.io.Serializable;
import java.sql.*;
import java.util.*;

public class ConnPool implements java.io.Serializable{
  private String driver = null; //數(shù)據(jù)庫驅動程序對象
  private String url = null; //數(shù)據(jù)源的位置
  private int size = 0; //連接池的最大連接數(shù)目
  private String username = ""; //數(shù)據(jù)源的用戶名
  private String password = ""; //數(shù)據(jù)源的密碼
  private DbConn dc=null; 
  private Vector pool = null; //連接池中的連接列表

  public ConnPool(){}
  
  //設置數(shù)據(jù)庫驅動程序
  public void setDriver(String driver){
    if (driver!=null) this.driver=driver;
  }
  
  //獲取數(shù)據(jù)庫驅動程序
  public String getDriver(){
    return driver;
  }

  //設置數(shù)據(jù)源的位置
  public void setURL(String url){
    if (url!=null) this.url=url;
  }
  
  //獲取數(shù)據(jù)源的位置
  public String getURL(){
    return url;
  }
  
  //設置最大連接數(shù)
  public void setSize(int size){
    if (size>1) this.size=size;
  }
  
  //獲取最大連接數(shù)
  public int getSize(){
    return size;
  }
  
  //設置數(shù)據(jù)源的用戶名
  public void setUsername(String username){
    if (username!=null) this.username=username;
  }
  
  //獲取數(shù)據(jù)源的用戶名
  public String getUserName(){
    return username;
  }

  //設置數(shù)據(jù)源的密碼
  public void setPassword(String password){
    if (password!=null) this.password=password;
  }
  
  //獲取數(shù)據(jù)源的密碼
  public String getPassword(){
    return password;
  }

  //設置用于單個連接任務的DbConn對象
  public void setConnBean(DbConn dc){
    if (dc!=null) this.dc=dc;
  }
  
  //獲取用于單個連接任務的DbConn對象
  public DbConn getConnBean() throws Exception{
    Connection conn = getConnection();
    DbConn dc = new DbConn(conn); //實例化DbConn類
    dc.setInuse(true);  //設置此連接可用
    return dc;
  }

  //創(chuàng)建到數(shù)據(jù)庫的連接
  private Connection createConnection() throws Exception{
    Connection con = null;
    con = DriverManager.getConnection(url,username,password);
    return con;
  }
  
  //初始化連接池
  public synchronized void initializePool() throws Exception{
    if (driver==null) //如果沒有加載驅動
      throw new Exception("No Driver Provided!");
    if (url==null)  //如果沒有設置數(shù)據(jù)源的位置
      throw new Exception("No URL Proviced!");
    if (size<1) //如果當前沒有可用的連接
      throw new Exception("Connection Pool Size is less than 1!");
    try{
      Class.forName(driver);
      for (int i=0; i<size; i++){
      	//創(chuàng)建連接
        Connection con = createConnection();
        if (con!=null){
          //將指定連接加入連接向量末尾
          DbConn dc = new DbConn(con);
          addConnection(dc);
        }
      }
    }catch (Exception e){
      System.err.println(e.getMessage());
      throw new Exception(e.getMessage());
    }
  }

  //將指定連接加入連接向量末尾
  private void addConnection(DbConn conn){
    if (pool==null) pool=new Vector(size);
    pool.addElement(conn);
  }

  //釋放指定連接的資源
  public synchronized void releaseConnection(Connection con){
    for (int i=0; i<pool.size(); i++){
      DbConn connBean = (DbConn)pool.elementAt(i);
      if (connBean.getConnection()==con){
      	//尋找到指定連接，將其置為未使用狀態(tài)
        connBean.setInuse(false);
        break;
      }
    }
  }

  //從連接池得到一個連接
  public synchronized Connection getConnection() throws Exception{
    DbConn dc = null;
    for (int i=0; i<pool.size(); i++){
      dc = (DbConn)pool.elementAt(i); // 從連接列表中獲得所有連接
      if (dc.getInuse()==false){
      	//如果還有未使用的連接，則使用這個連接
        dc.setInuse(true);
        Connection con = dc.getConnection();
        return con;
      }
    }
    //如果連接都已使用，則新建一連接
    try{
      Connection con = createConnection();
      dc = new DbConn(con);
      dc.setInuse(true);
      pool.addElement(dc);
    }catch (Exception e){
      System.err.println(e.getMessage());
      throw new Exception(e.getMessage());
    }
    return dc.getConnection();
  }

  //清空連接池，釋放資源
  public synchronized void emptyPool(){
    for (int i=0; i<pool.size(); i++){
      DbConn connBean = (DbConn)pool.elementAt(i);
      if (dc.getInuse()==false)
        dc.close(); //釋放連接資源
      else{
        try{
          java.lang.Thread.sleep(20000);
          dc.close();
        }catch (InterruptedException ie){
          System.err.println(ie.getMessage());
        }
      }
    }
   }
}