一个连接池的例子（来自jive）（3）.txt

一个新的采集工具 一个新的采集工具 一个新的采集工具

作者：sonymusic
email: [e-mail]
日期：2001-5-17 11:34:25
//文件：DbConnectionDefaultPool.java的第三部分


		/**
		 * Returns the age of a connection -- the time since it was handed out to
		 * an application.
		 */
		public long getAge(Connection conn) { // Returns the age of the connection in millisec.
			int thisconn = idOfConnection(conn);
			return System.currentTimeMillis() - connLockTime[thisconn];
		}

		private void createConn(int i) throws SQLException {
			 Date now = new Date();
			 try {
				Class.forName (dbDriver);
				Properties dbProp = new Properties();
				//log.println("Creating.....");
				dbProp.put("user", dbLogin);
				dbProp.put("password", dbPassword);
				dbProp.put("characterEncoding","gb2112");
				//dbProp.put("useUnicode", "true");
		
				connPool[i] = DriverManager.getConnection
						  (dbServer,dbProp);
				//log.println("Created Ok...");
				connStatus[i]=0;
				connID[i]=connPool[i].toString();
				connLockTime[i]=0;
				connCreateDate[i] =  now.getTime();
			}
			catch (ClassNotFoundException e2) {}
				
			log.println(now.toString() + "  Opening connection " + String.valueOf(i) +
					" " + connPool[i].toString() + ":");
		}
	
		/**
		 * Shuts down the housekeeping thread and closes all connections
		 * in the pool. Call this method from the destroy() method of the servlet.
		 */

		/**
		 * Multi-phase shutdown.  having following sequence:
		 * <OL>
		 * <LI><code>getConnection()</code> will refuse to return connections.
		 * <LI>The housekeeping thread is shut down.<br>
		 *    Up to the time of <code>millis</code> milliseconds after shutdown of
		 *    the housekeeping thread, <code>freeConnection()</code> can still be
		 *    called to return used connections.
		 * <LI>After <code>millis</code> milliseconds after the shutdown of the
		 *    housekeeping thread, all connections in the pool are closed.
		 * <LI>If any connections were in use while being closed then a
		 *    <code>SQLException</code> is thrown.
		 * <LI>The log is closed.
		 * </OL><br>
		 * Call this method from a servlet destroy() method.
		 *
		 * @param      millis   the time to wait in milliseconds.
		 * @exception  SQLException if connections were in use after
		 * <code>millis</code>.
		 */
		public void destroy(int millis) throws SQLException {
	
			// Checking for invalid negative arguments is not necessary,
			// Thread.join() does this already in runner.join().

			// Stop issuing connections
			available=false;

			// Shut down the background housekeeping thread
			runner.interrupt();

			// Wait until the housekeeping thread has died.
			try { runner.join(millis); }
			catch(InterruptedException e){} // ignore
		
			// The housekeeping thread could still be running
			// (e.g. if millis is too small). This case is ignored.
			// At worst, this method will throw an exception with the
	        // clear indication that the timeout was too short.

			long startTime=System.currentTimeMillis();

			// Wait for freeConnection() to return any connections
			// that are still used at this time.
			int useCount;
			while((useCount=getUseCount())>0 && System.currentTimeMillis() - startTime <=  millis) {
				try { Thread.sleep(500); }
				catch(InterruptedException e) {} // ignore
			}

			// Close all connections, whether safe or not
			for(int i=0; i < currConnections; i++) {
				try {
					connPool[i].close();
				}
				catch (SQLException e1)
				{
					log.println("Cannot close connections on Destroy");
				}
			}

			if(useCount > 0) {
				//bt-test successful
				String msg="Unsafe shutdown: Had to close "+useCount+
		            " active DB connections after "+millis+"ms";
				log.println(msg);
				// Close all open files
				log.close();
				// Throwing following Exception is essential because servlet authors
				// are likely to have their own error logging requirements.
				throw new SQLException(msg);
			}

			// Close all open files
			log.close();

		}//End destroy()


		/**
		 * Less safe shutdown.  Uses default timeout value.
		 * This method simply calls the <code>destroy()</code> method
		 * with a <code>millis</code>
		 * value of 10000 (10 seconds) and ignores <code>SQLException</code>
		 * thrown by that method.
		 * @see     #destroy(int)
		 */
		public void destroy() {
			try {
				destroy(10000);
			}
			catch(SQLException e) {}
		}

		/**
		 * Returns the number of connections in use.
		 */
		// This method could be reduced to return a counter that is
		// maintained by all methods that update connStatus.
		// However, it is more efficient to do it this way because:
		// Updating the counter would put an additional burden on the most
		// frequently used methods; in comparison, this method is
		// rarely used (although essential).
		public int getUseCount() {
			int useCount=0;
			synchronized(connStatus) {
				for(int i=0; i < currConnections; i++) {
					if(connStatus[i] > 0) { // In use
						useCount++;
					}
				}
			}
			return useCount;
		}//End getUseCount()

		/**
		 * Returns the number of connections in the dynamic pool.
		 */
		public int getSize() {
			return currConnections;
		}//End getSize()

	}

	/**
	 * An implementation of the Connection interface that wraps an underlying
	 * Connection object. It releases the connection back to a connection pool
	 * when Connection.close() is called.
	 */
	public class ConnectionWrapper  implements Connection {

		private Connection connection;
		private ConnectionPool connectionPool;

		public ConnectionWrapper(Connection connection, ConnectionPool connectionPool) {
			this.connection = connection;
			this.connectionPool = connectionPool;
		}

		/**
		 * Instead of closing the underlying connection, we simply release
		 * it back into the pool.
		 */
		public void close() throws SQLException {
			connectionPool.freeConnection(this.connection);
			//Release object references. Any further method calls on the
			//connection will fail.
			connection = null;
			connectionPool = null;
		}

		public Statement createStatement() throws SQLException {
			return connection.createStatement();
		}

		public PreparedStatement prepareStatement(String sql) throws SQLException {
			return connection.prepareStatement(sql);
		}

		public CallableStatement prepareCall(String sql) throws SQLException {
			return connection.prepareCall(sql);
		}

		public String nativeSQL(String sql) throws SQLException {
			return connection.nativeSQL(sql);
		}

		public void setAutoCommit(boolean autoCommit) throws SQLException {
			connection.setAutoCommit(autoCommit);
		}

		public boolean getAutoCommit() throws SQLException {
			return connection.getAutoCommit();
		}

		public void commit() throws SQLException {
			connection.commit();
		}

		public void rollback() throws SQLException {
			connection.rollback();
		}

		public boolean isClosed() throws SQLException {
			return connection.isClosed();
		}

		public DatabaseMetaData getMetaData() throws SQLException {
			return connection.getMetaData();
		}

		public void setReadOnly(boolean readOnly) throws SQLException {
			connection.setReadOnly(readOnly);
		}

		public boolean isReadOnly() throws SQLException {
			return connection.isReadOnly();
		}

		public void setCatalog(String catalog) throws SQLException {
			connection.setCatalog(catalog);
		}

		public String getCatalog() throws SQLException {
			return connection.getCatalog();
		}

		public void setTransactionIsolation(int level) throws SQLException {
			connection.setTransactionIsolation(level);
		}

		public int getTransactionIsolation() throws SQLException {
			return connection.getTransactionIsolation();
		}

		public SQLWarning getWarnings() throws SQLException {
			return connection.getWarnings();
		}

		public void clearWarnings() throws SQLException {
			connection.clearWarnings();
		}

		public Statement createStatement(int resultSetType, int resultSetConcurrency)
				throws SQLException
		{
			return connection.createStatement(resultSetType, resultSetConcurrency);
		}

		public PreparedStatement prepareStatement(String sql, int resultSetType,
				int resultSetConcurrency) throws SQLException
		{
			return connection.prepareStatement(sql, resultSetType, resultSetConcurrency);
		}

		public CallableStatement prepareCall(String sql, int resultSetType,
				int resultSetConcurrency) throws SQLException
		{
			return prepareCall(sql, resultSetType, resultSetConcurrency);
		}

		public Map getTypeMap() throws SQLException {
			return connection.getTypeMap();
		}

		public void setTypeMap(Map map) throws SQLException {
			connection.setTypeMap(map);
		}

	}
}