失眠网 > Alibaba Druid 源码阅读（五）数据库连接池连接关闭探索

Alibaba Druid 源码阅读（五）数据库连接池连接关闭探索

时间：2018-09-30 18:59:12

简介

在上文中探索了数据库连接池的获取，下面接着初步来探索下数据库连接的关闭，看看其中具体执行了那些操作

连接关闭

下面的具体的代码，相关的位置，加上了自己的注释：

@Overridepublic void close() throws SQLException {// 下面两段检查避免重复关闭if (this.disable) {return;}DruidConnectionHolder holder = this.holder;if (holder == null) {if (dupCloseLogEnable) {LOG.error("dup close");}return;}// 判断是否是一样的线程，不是则使用异步关闭DruidAbstractDataSource dataSource = holder.getDataSource();boolean isSameThread = this.getOwnerThread() == Thread.currentThread();if (!isSameThread) {dataSource.setAsyncCloseConnectionEnable(true);}if (dataSource.isAsyncCloseConnectionEnable()) {syncClose();return;}if (!pareAndSet(this, 0, 1)) {return;}try {// 连接关闭时的一些增强？for (ConnectionEventListener listener : holder.getConnectionEventListeners()) {listener.connectionClosed(new ConnectionEvent(this));}// Filter也能作用到连接关闭时?List<Filter> filters = dataSource.getProxyFilters();if (filters.size() > 0) {FilterChainImpl filterChain = new FilterChainImpl(dataSource);filterChain.dataSource_recycle(this);} else {recycle();}} finally {CLOSING_UPDATER.set(this, 0);}this.disable = true;}public void recycle() throws SQLException {if (this.disable) {return;}DruidConnectionHolder holder = this.holder;if (holder == null) {if (dupCloseLogEnable) {LOG.error("dup close");}return;}if (!this.abandoned) {DruidAbstractDataSource dataSource = holder.getDataSource();dataSource.recycle(this);}this.holder = null;conn = null;transactionInfo = null;closed = true;}

下面是具体的recycle()函数内容：

/*** 回收连接*/protected void recycle(DruidPooledConnection pooledConnection) throws SQLException {final DruidConnectionHolder holder = pooledConnection.holder;if (holder == null) {LOG.warn("connectionHolder is null");return;}// 一个warn，并没有直接返回if (logDifferentThread //&& (!isAsyncCloseConnectionEnable()) //&& pooledConnection.ownerThread != Thread.currentThread()//) {LOG.warn("get/close not same thread");}final Connection physicalConnection = holder.conn;// 使用双重检查锁，将traceEnable,目前尚不清楚其具体作用if (pooledConnection.traceEnable) {Object oldInfo = null;activeConnectionLock.lock();try {if (pooledConnection.traceEnable) {oldInfo = activeConnections.remove(pooledConnection);pooledConnection.traceEnable = false;}} finally {activeConnectionLock.unlock();}if (oldInfo == null) {if (LOG.isWarnEnabled()) {LOG.warn("remove abandonded failed. activeConnections.size " + activeConnections.size());}}}final boolean isAutoCommit = holder.underlyingAutoCommit;final boolean isReadOnly = holder.underlyingReadOnly;final boolean testOnReturn = this.testOnReturn;try {// check need to rollback?if ((!isAutoCommit) && (!isReadOnly)) {pooledConnection.rollback();}// reset holder, restore default settings, clear warningsboolean isSameThread = pooledConnection.ownerThread == Thread.currentThread();if (!isSameThread) {final ReentrantLock lock = pooledConnection.lock;lock.lock();try {holder.reset();} finally {lock.unlock();}} else {holder.reset();}if (holder.discard) {return;}// 如果计数标识大于配置的最大数，则关闭连接if (phyMaxUseCount > 0 && holder.useCount >= phyMaxUseCount) {// 关闭了连接// 同时如果活跃连接数小于配置的最小活跃数，会发送通知（具体作用后面再查看）discardConnection(holder);return;}// 计数标识设置if (physicalConnection.isClosed()) {lock.lock();try {if (holder.active) {activeCount--;holder.active = false;}closeCount++;} finally {lock.unlock();}return;}// 检测连接是否还有效，无效则返还，并设置计数标识位if (testOnReturn) {boolean validate = testConnectionInternal(holder, physicalConnection);if (!validate) {JdbcUtils.close(physicalConnection);destroyCountUpdater.incrementAndGet(this);lock.lock();try {if (holder.active) {activeCount--;holder.active = false;}closeCount++;} finally {lock.unlock();}return;}}if (holder.initSchema != null) {holder.conn.setSchema(holder.initSchema);holder.initSchema = null;}// 这里又关闭了一次连接// 在非enable的情况下if (!enable) {discardConnection(holder);return;}boolean result;final long currentTimeMillis = System.currentTimeMillis();// 连接超时关闭？这个超时具体是指什么还没搞清楚if (phyTimeoutMillis > 0) {long phyConnectTimeMillis = currentTimeMillis - holder.connectTimeMillis;if (phyConnectTimeMillis > phyTimeoutMillis) {discardConnection(holder);return;}}// 设置计数标识，同时没有关闭连接，而是放入池中lock.lock();try {if (holder.active) {activeCount--;holder.active = false;}closeCount++;result = putLast(holder, currentTimeMillis);recycleCount++;} finally {lock.unlock();}if (!result) {JdbcUtils.close(holder.conn);LOG.info("connection recyle failed.");}} catch (Throwable e) {// 异常情况下关闭连接holder.clearStatementCache();if (!holder.discard) {discardConnection(holder);holder.discard = true;}LOG.error("recyle error", e);recycleErrorCountUpdater.incrementAndGet(this);}}