谁能给我发一段完整的数据库连接池代码？

Answer 1

数据库连接是最常用的提高性能的方法，总结了一下：1 定义数据库访问接口public interface IDatabaseConnection
{
public abstract Connection createConnection();
public abstract void closeConnection(Connection conn);
}2 实现该接口2.1 直接连接，连接速度较慢，用户量较大时资源占用很大public Connection createConnection()
{
try
{
SystemParameter SP = new SystemParameter();
Class.forName(DBDRIVER).newInstance();
Connection con =
DriverManager.getConnection(
DBDRIVER_URL,
DBUSER,
DBPASSWORD);
return con;
}
catch (ClassNotFoundException e)
{
e.printStackTrace();
return null;
}
catch (SQLException e)
{ e.printStackTrace();
return null;
}
catch (InstantiationException e)
{ e.printStackTrace();
return null;
}
catch (IllegalAccessException e)
{ e.printStackTrace();
return null;
}
}
public void closeConnection(Connection conn)
{
if(conn!=null) try
{
conn.close();
}
catch (SQLException e)
{

e.printStackTrace();
} }2.2 DBConnectionManager、DBConnectionPool方式这个连接池是网上比较多的连接池代码public class DBConnectionManager
{
static private DBConnectionManager instance; /*唯一实例*/
static private int clients;
/*该计数代表引用DBConnectionManager唯一实例的客户程序总数，
它将被用于控制连接池的关闭操作 */
//Added by leo on 2001-5-23
static private String DEFAULTCONNECTIONPOOL = "homepage"; private Vector drivers = new Vector();
private PrintWriter logPrint;
private Hashtable pools = new Hashtable();
private SystemParameter sp = new SystemParameter();
/**
返回唯一实例。如果是第一次调用此方法，则创建实例
*/
static synchronized public DBConnectionManager getInstance()
{
if (instance == null)
{
instance = new DBConnectionManager();
}
clients++;
return instance;
} /**
建构函数私有以防止其它对象创建本类实例
*/
public DBConnectionManager()
{
init();
} /** Added by leo on 2001-5-23
使用默认的连接池名,创建并返回新连接
*
* @return Connection 可用连接或null
*/
public Connection getConnection()
{
return getConnection(DEFAULTCONNECTIONPOOL);
} /**
获得一个可用的(空闲的)连接.如果没有可用连接,且已有连接数小于最大连接数
限制,则创建并返回新连接
*
* @param name 在属性文件中定义的连接池名字
* @return Connection 可用连接或null
*/
public Connection getConnection(String name)
{
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null)
{
return pool.getConnection();
}
return null;
} /**
获得一个可用连接.若没有可用连接,且已有连接数小于最大连接数限制,
则创建并返回新连接.否则,在指定的时间内等待其它线程释放连接.
*
* @param name 连接池名字
* @param time 以毫秒计的等待时间
* @return Connection 可用连接或null
*/
public Connection getConnection(String name, long time)
{
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null)
{
return pool.getConnection(time);
}
return null;
} /** Added by leo on 2001-5-23
将连接对象返回给默认的连接池
*
* @param con 连接对象
*/
public void freeConnection(Connection con)
{
String name = DEFAULTCONNECTIONPOOL;
freeConnection(name, con);
} /**
将连接对象返回给由名字指定的连接池
*
* @param name 在属性文件中定义的连接池名字
* @param con 连接对象
*/
public void freeConnection(String name, Connection con)
{
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null)
{
pool.freeConnection(con);
}
} /**
关闭所有连接,撤销驱动程序的注册
*/
public synchronized void release()
{ // 等待直到最后一个客户程序调用
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() + "的注册");
}
catch (SQLException e)
{
log(e, "无法撤消下列JDBC驱动程序的注册" + driver.getClass().getName());
}
}
} /**
根据指定属性创建连接池实例.
*
* @param props 连接池属性
*/
private void createPools()
{

String poolName = sp.DBPOOLNAME;
String url = sp.DBDRIVER_URL;
String user = sp.DBUSER;
String password = sp.DBPASSWORD;
int max = sp.DBMAXCONN;

DBConnectionPool pool =
new DBConnectionPool(poolName, url, user, password, max);
pools.put(poolName, pool);
log("成功创建连接池" + poolName); } /**
读取属性完成初始化
*/
private void init()
{ logPrint=new PrintWriter(System.out);
loadDrivers();
createPools();
} /**
装载和注册所有JDBC驱动程序
*
* @param props 属性
*/
private void loadDrivers()
{

String driverClassName = sp.DBDRIVER;
try
{
Driver driver =
(Driver) Class.forName(driverClassName).newInstance();
DriverManager.registerDriver(driver);
drivers.addElement(driver);
log("成功JDBC注册驱动程序" + driverClassName);
}
catch (Exception e)
{
log("无法注册JDBC驱动程序；" + driverClassName + "，错误：" + e);
}

} /**
将文本信息写入日志文件
缺省为packaged
*/
void log(String msg)
{
logPrint.println(new java.util.Date() + ": " + msg);
} /**
将文本信息与异常写入日志文件
*/
void log(Throwable e, String msg)
{
logPrint.println(new java.util.Date() + ": " + msg);
e.printStackTrace(logPrint);
}}------------------------------------------------------class DBConnectionPool
{
private int checkedOut;
private PrintWriter logPrint;
private Vector freeConnections = new Vector();
private int maxConn;
private String name;
private String password;
private String URL;
private String user; /**
创建新的连接池
*@param name 连接池名字
*@param URL 数据库的JDBC URL
*@param user 数据库帐号,或null
*@param password 密码,或null
*@param maxConn 此连接池允许建立的最大连接数
*/
public DBConnectionPool(String name, String URL, String user, String password, int maxConn)
{
this.name = name;
this.URL = URL;
this.user = user;
this.password = password;
this.maxConn = maxConn;
logPrint = new PrintWriter(System.out);

} /**
将不再使用的连接返回给连接池
*@param con 客户程序释放的连接
*/
public synchronized void freeConnection(Connection con)
{
freeConnections.addElement(con);
checkedOut--;
notifyAll();
} /**
从连接池获得一个可用连接，如没有空闲的连接且当前连接数小于最大连接数，则创建新连接，
如原来登记为可用的连接不再有效，则从向量删除之，然后递归调用自己以尝试新的可用连接
*/
public synchronized Connection getConnection()
{
Connection con = null;
if(freeConnections.size() > 0)
{// 获取向量中第一个可用连接
con = (Connection)freeConnections.firstElement();
freeConnections.removeElementAt(0);
try
{
if(con.isClosed())
{
log("从连接池" + name + "删除一个无效连接");
con = getConnection();
}
}
catch(SQLException e)
{
log("从连接池" + name + "删除一个无效连接");
con = getConnection();
}
}
else if(maxConn == 0 || checkedOut < maxConn)
{
con = newConnection();
}
if(con != null)
{
checkedOut++;
}
return con;
} /**
从连接池获取可用连接，可以指定客户程序能够等待的最长时间
*@param timeout 以毫秒计的等待时间限制
*/
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;
} /**
关闭所有连接
*/
public synchronized void release()
{
Enumeration allConnections = freeConnections.elements();
while(allConnections.hasMoreElements())
{
Connection con = (Connection)allConnections.nextElement();
try
{
con.close();
log("关闭连接池" + name + "中的一个连接");
}
catch(SQLException e)
{
log(e, "无法关闭连接池" + name + "中的连接");
}
}
freeConnections.removeAllElements();
} /**
创建新的连接
*/
private Connection newConnection()
{
Connection con = null;
try
{
if(user == null)
{
con = DriverManager.getConnection(URL);
}
else
{
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;
} /**
将文本信息写入日志文件
缺省为packaged
*/
void log(String msg)
{
logPrint.println(new Date() + ": " + msg);
} /**
将文本信息与异常写入日志文件
*/
void log(Throwable e, String msg)
{
logPrint.println(new Date() + ": " + msg);
e.printStackTrace(logPrint);
}
}
---------------------------------DBConnectionManager connMgr = DBConnectionManager.getInstance();
public Connection createConnection()
{ Connection dBConn = connMgr.getConnection(new SystemParameter().DBPOOLNAME);
return dBConn;
} public void closeConnection(Connection conn)
{
connMgr.freeConnection(new SystemParameter().DBPOOLNAME, conn);
connMgr.release(); }
经过测试，使用这种方法，会造成数据库大量死锁，证明该连接池实现方法存在隐患也可能是因为它不属于webserver容器自身的，不具有可管理性。2.3 tomcat连接池public Connection createConnection()
{ try
{
Context initCtx = new InitialContext();
DataSource ds;
ds = (DataSource) initCtx.lookup("java:comp/env/"+new SystemParameter().JDBC_SOURCE);
return ds.getConnection();
}
catch (NamingException e)
{ e.printStackTrace();
return null;
}
catch (SQLException e)
{ e.printStackTrace();
return null;
} } public void closeConnection(Connection conn)
{
if(conn!=null)try
{
conn.close();
conn=null;
}
catch (SQLException e)
{

e.printStackTrace();
}

}2.4 weblogic连接池public Connection createConnection()
{
Context ctx = null;
Hashtable ht = new Hashtable();
ht.put(Context.INITIAL_CONTEXT_FACTORY, CONTEXT_FACTORY);
ht.put(Context.PROVIDER_URL, URL);
// ht.put(Context.SECURITY_PRINCIPAL, "admin");
// ht.put(Context.SECURITY_CREDENTIALS, "11111111"); Connection conn = null; try
{
ctx = new InitialContext(ht);
DataSource ds = (DataSource) ctx.lookup(POOL_NAME);
return ds.getConnection();
}
catch (NamingException e)
{ e.printStackTrace();
}
catch (SQLException e)
{ e.printStackTrace();
}
return null; } public void closeConnection(Connection conn)
{
if (conn != null)
try
{
conn.close();
conn = null;
}
catch (SQLException e)
{ e.printStackTrace();
} }3，4的方法比较好