druid获取链接Connection

public DruidPooledConnection getConnectionDirect(long maxWaitMillis) throws SQLException { int notFullTimeoutRetryCnt = 0; for (;;) { // handle notFullTimeoutRetry DruidPooledConnection poolableConnection; try { poolableConnection = getConnectionInternal(maxWaitMillis);//先获取链接，如果超时就报错 } catch (GetConnectionTimeoutException ex) { if (notFullTimeoutRetryCnt <= this.notFullTimeoutRetryCount && !isFull()) { notFullTimeoutRetryCnt++; if (LOG.isWarnEnabled()) { LOG.warn("get connection timeout retry : " + notFullTimeoutRetryCnt); } continue; } throw ex; } if (testOnBorrow) { //测试数据库是否可用 boolean validate = testConnectionInternal(poolableConnection.holder, poolableConnection.conn); if (!validate) { if (LOG.isDebugEnabled()) { LOG.debug("skip not validate connection."); } Connection realConnection = poolableConnection.conn; discardConnection(realConnection); continue; } } else { Connection realConnection = poolableConnection.conn; //使用之前检查链接是否还是有效的 if (poolableConnection.conn.isClosed()) { discardConnection(null); // 传入null，避免重复关闭 continue; } if (testWhileIdle) { final DruidConnectionHolder holder = poolableConnection.holder; long currentTimeMillis = System.currentTimeMillis(); long lastActiveTimeMillis = holder.lastActiveTimeMillis; long lastKeepTimeMillis = holder.lastKeepTimeMillis; if (lastKeepTimeMillis > lastActiveTimeMillis) { lastActiveTimeMillis = lastKeepTimeMillis; } long idleMillis = currentTimeMillis - lastActiveTimeMillis; long timeBetweenEvictionRunsMillis = this.timeBetweenEvictionRunsMillis; if (timeBetweenEvictionRunsMillis <= 0) { timeBetweenEvictionRunsMillis = DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS; } if (idleMillis >= timeBetweenEvictionRunsMillis || idleMillis < 0 // unexcepted branch ) { boolean validate = testConnectionInternal(poolableConnection.holder, poolableConnection.conn); if (!validate) { if (LOG.isDebugEnabled()) { LOG.debug("skip not validate connection."); } discardConnection(realConnection); continue; } } } } if (removeAbandoned) {//是否需要保留？ //不明白为什么要检测这个步骤 StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace(); poolableConnection.connectStackTrace = stackTrace; poolableConnection.setConnectedTimeNano(); poolableConnection.traceEnable = true; activeConnectionLock.lock(); try { //所有可用的链接 activeConnections.put(poolableConnection, PRESENT); } finally { activeConnectionLock.unlock(); } } if (!this.defaultAutoCommit) { //设置了是否自动提交 poolableConnection.setAutoCommit(false); } return poolableConnection; } }