1、简介
在本文中，我们将了解 com.alibaba.druid.pool.DruidDataSource#getConnection() 方法的执行流程。
2、环境
os-window10druid-1.2.8jdk-1.8.0_312maven-3.8.1
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3、获取连接流程
1、调用 com.alibaba.druid.pool.DruidDataSource#getConnection(long)重载方法
@Overridepublic DruidPooledConnection getConnection() throws SQLException { return getConnection(maxWait);}
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2、执行 init()初始化方法，如果 Filter 集合不为空则利用责任链模式执行 Filter 的 dataSource_getConnection 方法。
public DruidPooledConnection getConnection(long maxWaitMillis) throws SQLException { init();
if (filters.size() > 0) { FilterChainImpl filterChain = new FilterChainImpl(this); return filterChain.dataSource_connect(this, maxWaitMillis); } else { return getConnectionDirect(maxWaitMillis); }}
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3、最后都是执行 com.alibaba.druid.pool.DruidDataSource#getConnectionDirect 方法。getConnectionDirect 代码逻辑如下：
3.1、执行 com.alibaba.druid.pool.DruidDataSource#getConnectionInternal 方法
DruidPooledConnection poolableConnection;try { poolableConnection = getConnectionInternal(maxWaitMillis);} catch (GetConnectionTimeoutException ex) { if (notFullTimeoutRetryCnt <= this.notFullTimeoutRetryCount && !isFull()) { notFullTimeoutRetryCnt++; if (LOG.isWarnEnabled()) { LOG.warn("get connection timeout retry : " + notFullTimeoutRetryCnt); } continue; } throw ex;}
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3.2、testOnBorrow 参数为 true 时检查连接是否可用，不可用的连接进行丢弃处理
if (testOnBorrow) {boolean validate = testConnectionInternal(poolableConnection.holder, poolableConnection.conn);if (!validate) {if (LOG.isDebugEnabled()) {LOG.debug("skip not validate connection.");}
discardConnection(poolableConnection.holder);continue;}}
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3.3、testOnBorrow 参数为 false 时的执行流程如下：
3.3.1、检查连接是否被关闭
if (poolableConnection.conn.isClosed()) { discardConnection(poolableConnection.holder); // 传入null，避免重复关闭 continue;}
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3.3.2、检查是否配置了 testWhileIdle、removeAbandoned 参数，并根据配置做相应的处理。
if (testWhileIdle) { final DruidConnectionHolder holder = poolableConnection.holder; long currentTimeMillis = System.currentTimeMillis(); long lastActiveTimeMillis = holder.lastActiveTimeMillis; long lastExecTimeMillis = holder.lastExecTimeMillis; long lastKeepTimeMillis = holder.lastKeepTimeMillis;
if (checkExecuteTime && lastExecTimeMillis != lastActiveTimeMillis) { lastActiveTimeMillis = lastExecTimeMillis; }
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(poolableConnection.holder); continue; } }}}
if (removeAbandoned) { StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace(); poolableConnection.connectStackTrace = stackTrace; poolableConnection.setConnectedTimeNano(); poolableConnection.traceEnable = true;
activeConnectionLock.lock(); try { activeConnections.put(poolableConnection, PRESENT); } finally { activeConnectionLock.unlock(); }}
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3.3.3、检查是否默认自动提交
if (!this.defaultAutoCommit) { poolableConnection.setAutoCommit(false);}
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