package chapter10;

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

public class ConnPool implements java.io.Serializable{
  private String driver = null;
  private String url = null;
  private int size = 0;
  private String username = "";
  private String password = "";
  private DbConn dc=null;
  private Vector pool = null;

  public ConnPool(){}

  public void setDriver(String driver){
    if (driver!=null) this.driver=driver;
  }
  public String getDriver(){
    return driver;
  }

  public void setURL(String url){
    if (url!=null) this.url=url;
  }
  public String getURL(){
    return url;
  }

  public void setSize(int size){
    if (size>1) this.size=size;
  }
  public int getSize(){
    return size;
  }

  public void setUsername(String username){
    if (username!=null) this.username=username;
  }
  public String getUserName(){
    return username;
  }

  public void setPassword(String password){
    if (password!=null) this.password=password;
  }
  public String getPassword(){
    return password;
  }
//以上主要是設置其數據的連接參數
  public void setConnBean(DbConn dc){
    if (dc!=null) this.dc=dc;
  }
  public DbConn getConnBean() throws Exception{
    Connection conn = getConnection();
    DbConn dc = new DbConn(conn);
    dc.setInuse(true);
    return dc;
  }

  private Connection createConnection() throws Exception{
    Connection con = null;
    con = DriverManager.getConnection(url,username,password);
    return con;
  }

  public synchronized void initializePool() throws Exception{
    if (driver==null)
      throw new Exception("No Driver Provided!");
    if (url==null)
      throw new Exception("No URL Proviced!");
    if (size<1)
      throw new Exception("Connection Pool Size is less then 1!");
    try{
      Class.forName(driver);
      for (int i=0; i<size; i++){
        Connection con = createConnection();
        if (con!=null){
          DbConn dc = new DbConn(con);
          addConnection(dc);
        }
      }
    }catch (Exception e){
      System.err.println(e.getMessage());
      throw new Exception(e.getMessage());
    }
  }

  private void addConnection(DbConn conn){
    if (pool==null) pool=new Vector(size);
    pool.addElement(conn);
  }

  public synchronized void releaseConnection(Connection con){
    for (int i=0; i<pool.size(); i++){
      DbConn connBean = (DbConn)pool.elementAt(i);
      if (connBean.getConnection()==con){
        System.err.println("Release No." + i + " Connection!");
        connBean.setInuse(false);
        break;
      }
    }
  }

  public synchronized Connection getConnection() throws Exception{
    DbConn dc = null;
    for (int i=0; i<pool.size(); i++){
      dc = (DbConn)pool.elementAt(i);
      if (dc.getInuse()==false){
        dc.setInuse(true);
        Connection con = dc.getConnection();
        return con;
      }
    }
    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();
  }

  public synchronized void emptyPool(){
    for (int i=0; i<pool.size(); i++){
      System.err.println("Close No." + i + " JDBC Connection!");
      DbConn connBean = (DbConn)pool.elementAt(i);
      if (dc.getInuse()==false)
        dc.close();
      else{
        try{
          java.lang.Thread.sleep(20000);
          dc.close();
        }catch (InterruptedException ie){
          System.err.println(ie.getMessage());
        }
      }
    }
   }
}
//連接數據庫的javabean
class DbConn implements java.io.Serializable{
  private Connection conn = null;
  private boolean inuse = false;

  public DbConn(){}
  public DbConn(Connection conn){
    if (conn!=null) this.conn = conn;
  }

  public Connection getConnection(){
    return conn;
  }
  public void setConnection(Connection conn){
    this.conn = conn;
  }

  public void setInuse(boolean inuse){
    this.inuse = inuse;
  }
  public boolean getInuse(){
    return inuse;
  }

  public void close(){
    try{
      conn.close();
    }catch (SQLException sqle){
      System.err.println(sqle.getMessage());
    }
  }
}