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数据库连接池java实现小结 |
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作者：未知 来源：月光软件站 加入时间：2005-2-28 月光软件站 |
因为工作需要要使用到连接池，所以拜读了互联网上众多前辈的文章，学了不少经验，这里想做一个小结，加上自己的想法和在一起，希望能给大家一些帮助。
目的：
消除数据库频繁连接带来的开销和瓶颈。
解决方案：
不过多的限制用户的使用，既不能太多的要求用户按规定的方法得到和使用数据库连
尽量保持用户的习惯
目前的很多方法都是要求用户只能按规定方法使用连接，不能使用直接关闭数据连接的方法。解决办法就是使用代理类，来中间解决。可以参考http://www-900.ibm.com/developerWorks/cn/java/l-connpoolproxy/index.shtml
能维护连接的正常状态
因为针对数据库连接创建的资源，如果不能及时的释放，就会影响下一次数据连接的使用。例如在sql 2k中，一个连接不同创建多条Statement否则操作时会有数据连接占线的异常，所以必须在归还连接以后释放这些资源。
//判断是使用了createStatement语句
if (CREATESTATE.equals(method.getName()))
{
obj = method.invoke(conn, args);
statRef = (Statement)obj;//记录语句
return obj;
}
//判断是否调用了close的方法，如果调用close方法则把连接置为无用状态
if(CLOSE.equals(method.getName()))
{
//设置不使用标志
setIsFree(false);
//检查是否有后续工作，清除该连接无用资源
if (statRef != null)
statRef.close();
if (prestatRef != null)
prestatRef.close();
return null;
}
正确保护类不被违例使用
一个考虑就是不能让用户随便使用代理类，而只能自己使用，一个就是用内部私有类，一个就是使用只有指定类才能调用的标志。我的实现就是采用后者。
/**
* 创建连接的工厂，只能让工厂调用
* @param factory 要调用工厂，并且一定被正确初始化
* @param param 连接参数
* @return 连接
*/ static public _Connection getConnection(ConnectionFactory factory, ConnectionParam param)
{
if (factory.isCreate())//判断是否正确初始化的工厂
{ _Connection _conn = new _Connection(param);
return _conn; }
else
return null;
}
提供良好的用户接口，简单实用
使用静态方法创建工厂，然后来得到连接，使用完全和普通的Connection方法一样，没有限制。同时为了方便，设置了连接参数类和工厂参数类。
ConnectionParam param = new ConnectionParam(driver,url,user,password);
ConnectionFactory cf = null;//new ConnectionFactory(param, new FactoryParam());
try
{
cf = new ConnectionFactory(param,new FactoryParam());
Connection conn1 = cf.getFreeConnection();
Connection conn2 = cf.getFreeConnection();
Connection conn3 = cf.getFreeConnection();
Statement stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery("select * from requests");
if (rs.next())
{
System.out.println("conn1 y");
}
else
{
System.out.println("conn1 n");
}
stmt.close();
conn1.close();
为了实现连接池的正常运作，使用了单态模
/** * 使用指定的参数创建一个连接池 */
public ConnectionFactory(ConnectionParam param, FactoryParam fparam) throws SQLException
{
//不允许参数为空
if ((param == null)||(fparam == null)) throw new SQLException("ConnectionParam和FactoryParam不能为空");
if (m_instance == null)
{
synchronized(ConnectionFactory.class)
{
if (m_instance == null)
{
//new instance
//参数定制
m_instance = new ConnectionFactory();
m_instance.connparam = param;
m_instance.MaxConnectionCount = fparam.getMaxConn();
m_instance.MinConnectionCount = fparam.getMinConn();
m_instance.ManageType = fparam.getType();
m_instance.isflag = true;
//初始化，创建MinConnectionCount个连接
System.out.println("connection factory 创建！");
try
{
for (int i=0; i < m_instance.MinConnectionCount; i++)
{
_Connection _conn = _Connection.getConnection(m_instance, m_instance.connparam);
if (_conn == null) continue;
System.out.println("connection创建");
m_instance.FreeConnectionPool.add(_conn);//加入空闲连接池
m_instance.current_conn_count ++; //标志是否支持事务
m_instance.supportTransaction = _conn.isSupportTransaction();
}
} catch(Exception e) {
e.printStackTrace();
} //根据策略判断是否需要查询
if (m_instance.ManageType != 0)
{
Thread t = new Thread(new FactoryMangeThread(m_instance));
t.start(); } } } } }
连接池的管理
对于连接池的管理，我是设想使用静态管理和动态管理两种策略，设置了最大限制，和恒定的连接数。使用了2个池，一个空闲池，一个使用池。静态就是使用的时候发现空闲连接不够再去检查。动态就是使用了一个线程定时检查。
//根据策略判断是否需要查询
if (m_instance.ManageType != 0)
{
Thread t = new Thread(new FactoryMangeThread(m_instance));
t.start();
}
//连接池调度线程
public class FactoryMangeThread implements Runnable
{
ConnectionFactory cf = null;
long delay = 1000;
public FactoryMangeThread(ConnectionFactory obj)
{
cf = obj;
}
/* (non-Javadoc)
* @see java.lang.Runnable#run()
*/
public void run()
{
while(true)
{
try
{
Thread.sleep(delay);
} catch(InterruptedException e){}
System.out.println("eeeee"); //判断是否已经关闭了工厂，那就退出监听
if (cf.isCreate())
cf.schedule();
else
System.exit(1); }}}
最后给出完整的源代码：
--------------------------------------------------------------------------------
_Connectio.java
package scut.ailab.connectionpool;
import java.lang.reflect.*;
import java.sql.*;
/**
* @author youyongming
* 定义数据库连接的代理类
*/
public class _Connection implements InvocationHandler
{
//定义连接 private Connection conn = null;
//定义监控连接创建的语句
private Statement statRef = null;
private PreparedStatement prestatRef = null;
//是否支持事务标志
private boolean supportTransaction = false;
//数据库的忙状态
private boolean isFree = false;
//最后一次访问时间
long lastAccessTime = 0;
//定义要接管的函数的名字
String CREATESTATE = "createStatement";
String CLOSE = "close"; String PREPARESTATEMENT = "prepareStatement";
String COMMIT = "commit";
String ROLLBACK = "rollback";
/**
* 构造函数，采用私有，防止被直接创建
* @param param 连接参数
*/
private _Connection(ConnectionParam param)
{
//记录日至
try{
//创建连接
Class.forName(param.getDriver()).newInstance();
conn = DriverManager.getConnection(param.getUrl(),param.getUser(), param.getPassword());
DatabaseMetaData dm = null;
dm = conn.getMetaData();
//判断是否支持事务
supportTransaction = dm.supportsTransactions();
} catch(Exception e) { e.printStackTrace(); } }
/**
* (non-Javadoc)
* @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
*/
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
{
Object obj = null;
//判断是否调用了close的方法，如果调用close方法则把连接置为无用状态
if(CLOSE.equals(method.getName()))
{
//设置不使用标志
setIsFree(false);
//检查是否有后续工作，清除该连接无用资源
if (statRef != null)
statRef.close();
if (prestatRef != null)
prestatRef.close(); return null; }
//判断是使用了createStatement语句
if (CREATESTATE.equals(method.getName()))
{
obj = method.invoke(conn, args);
statRef = (Statement)obj;
//记录语句
return obj; }
//判断是使用了prepareStatement语句
if (PREPARESTATEMENT.equals(method.getName()))
{ obj = method.invoke(conn, args); prestatRef = (PreparedStatement)obj; return obj; } //如果不支持事务，就不执行该事物的代码
if ((COMMIT.equals(method.getName())||ROLLBACK.equals(method.getName())) && (!isSupportTransaction()))
return null;
obj = method.invoke(conn, args);
//设置最后一次访问时间，以便及时清除超时的连接
lastAccessTime = System.currentTimeMillis();
return obj; }
/**
* 创建连接的工厂，只能让工厂调用
* @param factory 要调用工厂，并且一定被正确初始化
* @param param 连接参数
* @return 连接
*/
static public _Connection getConnection(ConnectionFactory factory, ConnectionParam param)
{
if (factory.isCreate())
//判断是否正确初始化的工厂
{ _Connection _conn = new _Connection(param);
return _conn;
}
else
return null;
}
public Connection getFreeConnection()
{
//返回数据库连接conn的接管类，以便截住close方法
Connection conn2 = (Connection)Proxy.newProxyInstance(conn.getClass().getClassLoader(), conn.getClass().getInterfaces(),this);
return conn2;
}
/**
* 该方法真正的关闭了数据库的连接
* @throws SQLException
*/
void close() throws SQLException
{
//由于类属性conn是没有被接管的连接，因此一旦调用close方法后就直接关闭连接
conn.close();
}
public void setIsFree(boolean value)
{ isFree = value; }
public boolean isFree() { return isFree; }
/**
* 判断是否支持事务
* @return boolean
*/
public boolean isSupportTransaction()
{ return supportTransaction; }
}
--------------------------------------------------------------------------------
ConnectionFactory.java
package scut.ailab.connectionpool;
/**
* @author youyongming
*/
import java.util.LinkedHashSet;import java.sql.*;
import java.util.Iterator;
public class ConnectionFactory
{ private static ConnectionFactory m_instance = null;
//在使用的连接池
private LinkedHashSet ConnectionPool = null;
//空闲连接池
private LinkedHashSet FreeConnectionPool = null;
//最大连接数
private int MaxConnectionCount = 4;
//最小连接数
private int MinConnectionCount = 2;
//当前连接数 private int current_conn_count = 0;
//连接参数
private ConnectionParam connparam = null;
//是否创建工厂的标志
private boolean isflag = false;
//是否支持事务
private boolean supportTransaction = false;
//定义管理策略
private int ManageType = 0;
private ConnectionFactory()
{
ConnectionPool = new LinkedHashSet();
FreeConnectionPool = new LinkedHashSet(); }
/**
* 使用指定的参数创建一个连接池
*/
public ConnectionFactory(ConnectionParam param, FactoryParam fparam) throws SQLException
{
//不允许参数为空
if ((param == null)||(fparam == null)) throw new SQLException("ConnectionParam和FactoryParam不能为空");
if (m_instance == null)
{
synchronized(ConnectionFactory.class)
{
if (m_instance == null)
{
//new instance
//参数定制
m_instance = new ConnectionFactory();
m_instance.connparam = param;
m_instance.MaxConnectionCount = fparam.getMaxConn();
m_instance.MinConnectionCount = fparam.getMinConn();
m_instance.ManageType = fparam.getType();
m_instance.isflag = true;
//初始化，创建MinConnectionCount个连接
System.out.println("connection factory 创建！");
try
{
for (int i=0; i < m_instance.MinConnectionCount; i++)
{
_Connection _conn = _Connection.getConnection(m_instance, m_instance.connparam);
if (_conn == null) continue;
System.out.println("connection创建");
m_instance.FreeConnectionPool.add(_conn);
//加入空闲连接池
m_instance.current_conn_count ++;
//标志是否支持事务
m_instance.supportTransaction = _conn.isSupportTransaction();
}
} catch(Exception e) { e.printStackTrace(); }
//根据策略判断是否需要查询
if (m_instance.ManageType != 0)
{
Thread t = new Thread(new FactoryMangeThread(m_instance));
t.start(); } } } } }
/**
* 标志工厂是否已经创建
* @return boolean
*/
public boolean isCreate()
{ return m_instance.isflag; }
/**
* 从连接池中取一个空闲的连接
* @return Connection
* @throws SQLException
*/ public synchronized Connection getFreeConnection() throws SQLException
{
Connection conn = null;
//获取空闲连接
Iterator iter = m_instance.FreeConnectionPool.iterator();
while(iter.hasNext())
{
_Connection _conn = (_Connection)iter.next();
//找到未用连接
if(!_conn.isFree())
{
conn = _conn.getFreeConnection();
_conn.setIsFree(true);
//移出空闲区
m_instance.FreeConnectionPool.remove(_conn);
//加入连接池
m_instance.ConnectionPool.add(_conn);
break; } }
//检查空闲池是否为空
if (m_instance.FreeConnectionPool.isEmpty())
{
//再检查是否能够分配
if (m_instance.current_conn_count < m_instance.MaxConnectionCount)
{
//新建连接到空闲连接池
int newcount = 0 ;
//取得要建立的数目
if (m_instance.MaxConnectionCount - m_instance.current_conn_count >=m_instance.MinConnectionCount)
{
newcount = m_instance.MinConnectionCount;
}
else
{
newcount = m_instance.MaxConnectionCount - m_instance.current_conn_count; }
//创建连接
for (int i=0;i {
_Connection _conn = _Connection.getConnection(m_instance, m_instance.connparam); m_instance.FreeConnectionPool.add(_conn);
m_instance.current_conn_count ++; } }
else {
//如果不能新建，检查是否有已经归还的连接
iter = m_instance.ConnectionPool.iterator();
while(iter.hasNext())
{ _Connection _conn = (_Connection)iter.next();
if(!_conn.isFree())
{
conn = _conn.getFreeConnection();
_conn.setIsFree(false);
m_instance.ConnectionPool.remove(_conn);
m_instance.FreeConnectionPool.add(_conn);
break; } } } }
if (FreeConnectionPool.isEmpty())
//再次检查是否能分配连接
if(conn == null)
{ iter = m_instance.FreeConnectionPool.iterator();
while(iter.hasNext())
{ _Connection _conn = (_Connection)iter.next();
if(!_conn.isFree())
{
conn = _conn.getFreeConnection();
_conn.setIsFree(true);
m_instance.FreeConnectionPool.remove(_conn);
m_instance.ConnectionPool.add(_conn); break; } }
if(conn == null)
//如果不能则说明无连接可用
throw new SQLException("没有可用的数据库连接"); }
System.out.println("get connection"); return conn; }
/**
* 关闭该连接池中的所有数据库连接
* @throws SQLException
*/
public synchronized void close() throws SQLException
{ this.isflag = false; SQLException excp = null;
//关闭空闲池
Iterator iter = m_instance.FreeConnectionPool.iterator();
while(iter.hasNext())
{
try{ ((_Connection)iter.next()).close(); System.out.println("close connection:free");
m_instance.current_conn_count --;
}catch(Exception e)
{ if(e instanceof SQLException)
excp = (SQLException)e; } }
//关闭在使用的连接池
iter = m_instance.ConnectionPool.iterator();
while(iter.hasNext())
{
try{
((_Connection)iter.next()).close();
System.out.println("close connection:inused");
m_instance.current_conn_count --;
}catch(Exception e)
{ if(e instanceof SQLException)
excp = (SQLException)e; } }
if(excp != null) throw excp; }
/**
* 返回是否支持事务
* @return boolean
*/
public boolean isSupportTransaction()
{
return m_instance.supportTransaction; }
/**
* 连接池调度管理
*
*/ public void schedule()
{ Connection conn = null;
//再检查是否能够分配
Iterator iter = null;
//检查是否有已经归还的连接
{
iter = m_instance.ConnectionPool.iterator();
while(iter.hasNext())
{ _Connection _conn = (_Connection)iter.next();
if(!_conn.isFree())
{ conn = _conn.getFreeConnection();
_conn.setIsFree(false);
m_instance.ConnectionPool.remove(_conn);
m_instance.FreeConnectionPool.add(_conn);
break; } } }
if (m_instance.current_conn_count < m_instance.MaxConnectionCount)
{
//新建连接到空闲连接池
int newcount = 0 ;
//取得要建立的数目
if (m_instance.MaxConnectionCount - m_instance.current_conn_count >=m_instance.MinConnectionCount)
{
newcount = m_instance.MinConnectionCount;
} else {
newcount = m_instance.MaxConnectionCount - m_instance.current_conn_count; }
//创建连接
for (int i=0;i {
_Connection _conn = _Connection.getConnection(m_instance, m_instance.connparam); m_instance.FreeConnectionPool.add(_conn);
m_instance.current_conn_count ++; } } }}
--------------------------------------------------------------------------------
ConnectionParam.java
package scut.ailab.connectionpool;
import java.io.Serializable;
/**
* @author youyongming
* 实现数据库连接的参数类
*/
public class ConnectionParam implements Serializable
{ private String driver; //数据库驱动程序
private String url; //数据连接的URL
private String user; //数据库用户名
private String password; //数据库密码
/**
* 唯一的构造函数，需要指定连接的四个必要参数
* @param driver 数据驱动
* @param url 数据库连接url
* @param user 用户名
* @param password 密码
*/
public ConnectionParam(String driver,String url,String user,String password)
{ this.driver = driver; this.url = url; this.user = user; this.password = password; }
public String getDriver() { return driver; }
public String getPassword() { return password; }
public String getUrl() { return url; }
public String getUser() { return user; }
public void setDriver(String driver) { this.driver = driver; }
public void setPassword(String password) { this.password = password; }
public void setUrl(String url) { this.url = url; }
public void setUser(String user) { this.user = user; }
/**
* @see java.lang.Object#clone()
*/
public Object clone()
{
ConnectionParam param = new ConnectionParam(driver,url,user,password); return param;
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
public boolean equals(Object obj)
{
if(obj instanceof ConnectionParam)
{
ConnectionParam param = (ConnectionParam)obj;
return ((driver.compareToIgnoreCase(param.getDriver()) == 0)&& (url.compareToIgnoreCase(param.getUrl()) == 0)&& (user.compareToIgnoreCase(param.getUser()) == 0)&& (password.compareToIgnoreCase(param.getPassword()) == 0)); }
return false;
}
}
--------------------------------------------------------------------------------
FactoryMangeThread.java
/* * Created on 2003-5-13 *
* To change the template for this generated file go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
package scut.ailab.connectionpool;
/**
* @author youyongming *
*/
//连接池调度线程
public class FactoryMangeThread implements Runnable
{
ConnectionFactory cf = null;
long delay = 1000;
public FactoryMangeThread(ConnectionFactory obj)
{ cf = obj; }
/* (non-Javadoc)
* @see java.lang.Runnable#run()
*/
public void run()
{ while(true)
{
try
{
Thread.sleep(delay);
} catch(InterruptedException e){}
System.out.println("eeeee");
//判断是否已经关闭了工厂，那就退出监听
if (cf.isCreate())
cf.schedule();
else
System.exit(1); } }}
--------------------------------------------------------------------------------
FactoryParam.java
/* * Created on 2003-5-13 *
* To change the template for this generated file go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
package scut.ailab.connectionpool;
/**
* @author youyongming *
*///连接池工厂参数
public class FactoryParam
{
//最大连接数
private int MaxConnectionCount = 4;
//最小连接数
private int MinConnectionCount = 2;
//回收策略
private int ManageType = 0;
public FactoryParam() { }
/**
* 构造连接池工厂参数的对象
* @param max 最大连接数
* @param min 最小连接数
* @param type 管理策略
*/
public FactoryParam(int max, int min, int type)
{
this.ManageType = type;
this.MaxConnectionCount = max;
this.MinConnectionCount = min; }
/** * 设置最大的连接数
* @param value
*/
public void setMaxConn(int value)
{
this.MaxConnectionCount = value; }
/**
* 获取最大连接数
* @return
*/
public int getMaxConn()
{ return this.MaxConnectionCount; }
/**
* 设置最小连接数
* @param value
*/
public void setMinConn(int value)
{ this.MinConnectionCount = value; }
/**
* 获取最小连接数
* @return
*/
public int getMinConn()
{
return this.MinConnectionCount;
}
public int getType()
{ return this.ManageType;
}}
------------------------------------------------------------------------------
testmypool.java
/*
* Created on 2003-5-13
* To change the template for this generated file go to * Window>Preferences>Java>Code Generation>Code and Comments */
package scut.ailab.connectionpool;
/**
* @author youyongming *
*/
import java.sql.*;
public class testmypool
{
public void test1()
{
String user = "DevTeam";
String password = "DevTeam";
String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
String url = "jdbc:odbc:gfqh2";
ConnectionParam param = new ConnectionParam(driver,url,user,password);
ConnectionFactory cf = null;
new ConnectionFactory(param, new FactoryParam());
try{ cf = new ConnectionFactory(param,new FactoryParam());
Connection conn1 = cf.getFreeConnection();
Connection conn2 = cf.getFreeConnection();
Connection conn3 = cf.getFreeConnection();
Statement stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery("select * from requests");
if (rs.next())
{ System.out.println("conn1 y");
} else
{
System.out.println("conn1 n");
}
stmt.close();
conn1.close();
Connection conn4 = cf.getFreeConnection();
Connection conn5 = cf.getFreeConnection();
stmt = conn5.createStatement();
rs = stmt.executeQuery("select * from requests");
if (rs.next()) {
System.out.println("conn5 y");
} else {
System.out.println("conn5 n");
}
conn2.close();
conn3.close();
conn4.close();
conn5.close();
}
catch(Exception e)
{
e.printStackTrace(); }
finally
{
try
{
cf.close();
} catch(Exception e) {
e.printStackTrace();
} } }
public static void main(String[] args)
{ String user = "DevTeam";
String password = "DevTeam";
String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
String url = "jdbc:odbc:gfqh2";
ConnectionParam param = new ConnectionParam(driver,url,user,password);
ConnectionFactory cf = null;
new ConnectionFactory(param,new FactoryParam());
try{
cf = new ConnectionFactory(param,new FactoryParam());
ConnectionFactory cf1= new ConnectionFactory(param,new FactoryParam());
Connection conn1 = null;
long time = System.currentTimeMillis();
for (int i=0; i <10;i++)
{ conn1 = cf.getFreeConnection();
Statement stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery("select * from requests");
if (rs.next())
{ System.out.println("conn1 y"); }
else
{ System.out.println("conn1 n"); }
conn1.close(); }
System.out.println("pool:" + (System.currentTimeMillis()-time));
time = System.currentTimeMillis();
Class.forName(param.getDriver()).newInstance();
for (int i=0; i <10;i++)
{
conn1 = DriverManager.getConnection(param.getUrl(),param.getUser(), param.getPassword());
Statement stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery("select * from requests");
if (rs.next())
{
System.out.println("conn1 y");
} else {
System.out.println("conn1 n");
} conn1.close();
}
System.out.println("no pool:" + (System.currentTimeMillis()-time));
} catch(Exception e)
{ e.printStackTrace(); }
finally{
try{
cf.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
}
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相关文章：相关软件： |
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