数据库连接池java实现小结

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Java SQL JDBC thread 互联网

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 <newcount 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 <newcount 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(); } } } }</newcount></newcount>

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