二、得到和返回连接

　　DBConnectionManager提供getConnection（）方法和freeConnection方法，这些方法有客户程序使用。所有的方法以连接池名字所参数，并调用特定的连接池对象。

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;

}

public void freeConnection(String name, Connection con) {

DBConnectionPool pool = (DBConnectionPool) pools.get(name);

if (pool != null) {

pool.freeConnection(con);

}

}

　　三、关闭

　　最后，由一个release（）方法，用来完好地关闭连接池。每个DBConnectionManager客户必须调用getInstance()方法引用。有一个计数器跟踪客户的数量。方法release()在客户关闭时调用，技术器减1。当最后一个客户释放，DBConnectionManager关闭所有的连接池。

List 11-14

public synchronized void release() {

// Wait until called by the last client

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("Deregistered JDBC driver " + driver.getClass().getName());

}

catch (SQLException e) {

log(e, "Can not deregister JDBC driver: " +

driver.getClass().getName());

}

}

}

当所有连接池关闭，所有jdbc驱动程序也被注销。

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