package com.jewes;
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
//建立DBConnectionManager
public class DBConnectionManager
{static private DBConnectionManager instance;
static private int clients;
private Vector drivers=new Vector();
private PrintWriter log;
private Hashtable pools=new Hashtable();
//返回唯一的实列
static synchronized public DBConnectionManager getInstance()
{if(instance==null)
{instance=new DBConnectionManager();
} clients++;
return instance;
}
//构造函数！
private DBConnectionManager()
{init();
} //结束构造函数
//释放一个连接
public void freeConnection(String name,Connection con)
{DBConnectionPool pool=(DBConnectionPool)pools.get(name);
if(pool!=null)
{pool.freeConnection(con);
} }
//结束释放一个连接
//取得一个连接
public Connection getConnection(String name)
{DBConnectionPool pool=(DBConnectionPool)pools.get(name);
if(pool!=null)
{return pool.getConnection();
} return null;
}
public Connection getConnection(String name,long time)
{DBConnectionPool pool=(DBConnectionPool)pools.get(name);
if(pool!=null)
{return pool.getConnection(time);
} return null;
} //结束getconnection
//关闭所有连接
public synchronized void release()
{ {if(--clients!=0)
return;
} Enumeration allPools=pools.elements();
while(allPools.hasMoreElements())
{DBConnectionPool pool=(DBConnectionPool)allPools.nextElement();
pool.release();
} Enumeration allDrivers=drivers.elements();
while(allDrivers.hasMoreElements())
{Driver driver=(Driver)allDrivers.nextElement();
try
{DriverManager.deregisterDriver(driver);
log("撤消JDBC驱动程序"+driver.getClass().getName());
} catch(SQLException e)
{log(e,"无法撤消JDBC驱动程序的注册"+driver.getClass().getName());
} }
} private void createPools(Properties props)
{Enumeration propNames=props.propertyNames();
while(propNames.hasMoreElements())
{String name=(String) propNames.nextElement();
if(name.endsWith(".url"))
{String poolName=name.substring(0,name.lastIndexOf("."));
String url=props.getProperty(poolName+".url");
if(url==null)
{log("没有连接池"+poolName+"指定的URL");
continue;
} String user=props.getProperty(poolName+".user");
String password=props.getProperty(poolName+".password");
String maxconn= props.getProperty(poolName+".maxconn","0");
int max;
try
{max=Integer.valueOf(maxconn).intvalue();
} catch(NumberFormatException e)
{log("错误的最大连接数："+maxconn+".连接池"+poolName);
max=0;
} DBConnectionPool pool=new DBConnectionPool(poolName,url,user,password,max);
pools.put(poolName,pool);
log("成功创建连接池"+poolName);
} }
}
private void init()
{InputStream is=getClass().getResourceAsStream("/db.properties");
Properties dbProps=new Properties();
try
{dbProps.load(is);
} catch(Exception e)
{System.err.println("不能读取属性文件。请确保db.properties在你的CLASSPATH中");
return;
} String logFile=dbProps.getProperty("logfile","DBConnectionManager.log");
try
{log=new PrintWriter(new FileWriter(logFile,true),true);
} catch(IOException e)
{System.err.println("无法打开日志文件："+logFile);
log=new PrintWriter(System.err);
} loadDriver(dbProps);
createPools(dbProps);
}
private void loadDriver(Properties props)
{String driverClasses=props.getProperty("drivers");
StringTokenizer st=new StringTokenizer(driverClasses);
while(st.hasMoreElements())
{String driverClassName=st.nextToken().trim();
try
{Driver driver=(Driver)Class.forName(driverClassName).newInstance();
DriverManager.registerDriver(driver);
drivers.addElement(driver);
log("成功注册驱动程序"+driverClassName);
} catch(Exception e)
{log("无法注册驱动程序:"+driverClassName+",错误"+e);
} }
}
private void log(String msg)
{log.println(new Date()+":"+msg);
} private void log(Throwable e,String msg)
{log.println(new Date()+":"+msg);
e.printStackTrace(log);
} class DBConnectionPool
{private int checkOut;
private Vector freeConnections=new Vector();
private int maxconn;
private String name;
private String password;
private String URL;
private String user;
public DBConnectionPool(String name,String URL,String user,String password,int maxconn)
{this.name=name;
this.URL=URL;
this.password=password;
this.user=user;
this.maxconn=maxconn;
} public synchronized void freeConnection(Connection con)
{freeConnections.addElement(con);
checkOut--;
notifyAll();
} public synchronized Connection getConnection()
{Connection con=null;
if(freeConnections.size()>0)
{con=(Connection)freeConnections.firstElement();
freeConnections.removeElementAt(0);
try
{if(con.isClosed())
{log("从连接池"+name+"删除一个连接");
con=getConnection();
} }
catch(SQLException e)
{log("从连接池"+name+"删除一个连接");
con=getConnection();
} }
else if(maxconn==0||checkOut<maxconn)
{con=newConnection();
} if(con!=null)
{checkOut++;
} return con;
}
public synchronized Connection getConnection(long timeout)
{long startTime=new Date().getTime();
Connection con;
while((con=getConnection())==null)
{ try
{wait(timeout);
} catch(InterruptedException e)
{}
if((new Date().getTime()-startTime)>=timeout)
{return null;
} }
return con;
} public void release()
{Enumeration allConnections=freeConnections.elements();
while(allConnections.hasMoreElements())
{Connection con=(Connection)allConnections.nextElement();
try
{con.close();
log("关闭连接池"+name+"中的连接");
} catch(SQLException e)
{log(e,"无法关闭连接池"+name+"中的连接");
} }
freeConnections.removeAllElements();
} private Connection newConnection()
{Connection con=null;
try
{con=DriverManager.getConnection(URL,user,password);
log("连接池"+name+"创建一个新的连接");
} catch(SQLException e)
{log(e,"无法创建下列URL的连接"+URL);
return null;
} return con;
} }
}
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