700字范文 > Alibaba Druid 源码阅读（三）数据库连接池初始化探索

Alibaba Druid 源码阅读（三）数据库连接池初始化探索

时间：2018-12-10 23:17:25

简介

上文中探索了Alibaba Druid的连接池初始化和获取连接的关键代码，接下来详细看看初始化部分

数据库连接池初始化

对整个代码加上注释，如下：

public void init() throws SQLException {// 已经初始化过了，直接返回if (inited) {return;}// bug fixed for dead lock, for issue #2980DruidDriver.getInstance();// 初始化时上锁final ReentrantLock lock = this.lock;try {lock.lockInterruptibly();} catch (InterruptedException e) {throw new SQLException("interrupt", e);}boolean init = false;try {if (inited) {return;}initStackTrace = Utils.toString(Thread.currentThread().getStackTrace());// 这部分尚不清楚作用this.id = DruidDriver.createDataSourceId();if (this.id > 1) {long delta = (this.id - 1) * 100000;this.connectionIdSeedUpdater.addAndGet(this, delta);this.statementIdSeedUpdater.addAndGet(this, delta);this.resultSetIdSeedUpdater.addAndGet(this, delta);this.transactionIdSeedUpdater.addAndGet(this, delta);}// 数据库连接urlif (this.jdbcUrl != null) {this.jdbcUrl = this.jdbcUrl.trim();initFromWrapDriverUrl();}// filter相关，目前为空for (Filter filter : filters) {filter.init(this);}// 获取数据库类型if (this.dbTypeName == null || this.dbTypeName.length() == 0) {this.dbTypeName = JdbcUtils.getDbType(jdbcUrl, null);}// 针对 mysql、mariadb、oceanbase、ads 做其特有的处理DbType dbType = DbType.of(this.dbTypeName);if (dbType == DbType.mysql|| dbType == DbType.mariadb|| dbType == DbType.oceanbase|| dbType == DbType.ads) {boolean cacheServerConfigurationSet = false;if (this.connectProperties.containsKey("cacheServerConfiguration")) {cacheServerConfigurationSet = true;} else if (this.jdbcUrl.indexOf("cacheServerConfiguration") != -1) {cacheServerConfigurationSet = true;}if (cacheServerConfigurationSet) {this.connectProperties.put("cacheServerConfiguration", "true");}}// 下面就是一些配置的效验// 这部分是不是放到最前面比较好？if (maxActive <= 0) {throw new IllegalArgumentException("illegal maxActive " + maxActive);}if (maxActive < minIdle) {throw new IllegalArgumentException("illegal maxActive " + maxActive);}if (getInitialSize() > maxActive) {throw new IllegalArgumentException("illegal initialSize " + this.initialSize + ", maxActive " + maxActive);}if (timeBetweenLogStatsMillis > 0 && useGlobalDataSourceStat) {throw new IllegalArgumentException("timeBetweenLogStatsMillis not support useGlobalDataSourceStat=true");}if (maxEvictableIdleTimeMillis < minEvictableIdleTimeMillis) {throw new SQLException("maxEvictableIdleTimeMillis must be grater than minEvictableIdleTimeMillis");}if (keepAlive && keepAliveBetweenTimeMillis <= timeBetweenEvictionRunsMillis) {throw new SQLException("keepAliveBetweenTimeMillis must be grater than timeBetweenEvictionRunsMillis");}// driverClass相关if (this.driverClass != null) {this.driverClass = driverClass.trim();}// 下面这段有些初始化加载和检查，但不是看的太明白initFromSPIServiceLoader();resolveDriver();initCheck();initExceptionSorter();initValidConnectionChecker();validationQueryCheck();// Stat 的作用是啥，目前尚不清楚if (isUseGlobalDataSourceStat()) {dataSourceStat = JdbcDataSourceStat.getGlobal();if (dataSourceStat == null) {dataSourceStat = new JdbcDataSourceStat("Global", "Global", this.dbTypeName);JdbcDataSourceStat.setGlobal(dataSourceStat);}if (dataSourceStat.getDbType() == null) {dataSourceStat.setDbType(this.dbTypeName);}} else {dataSourceStat = new JdbcDataSourceStat(this.name, this.jdbcUrl, this.dbTypeName, this.connectProperties);}dataSourceStat.setResetStatEnable(this.resetStatEnable);// 关键的数据库连接池相关的，在获取连接中就是从DruidConnectionHolder中获取的connections = new DruidConnectionHolder[maxActive];evictConnections = new DruidConnectionHolder[maxActive];keepAliveConnections = new DruidConnectionHolder[maxActive];SQLException connectError = null;// 这段看大致意思的异步去生成数据库物理连接// 因为else中是可以看出直接获取了数据库的物理连接，然后放到DruidConnectionHolder中if (createScheduler != null && asyncInit) {for (int i = 0; i < initialSize; ++i) {submitCreateTask(true);}} else if (!asyncInit) {// init connectionswhile (poolingCount < initialSize) {try {PhysicalConnectionInfo pyConnectInfo = createPhysicalConnection();DruidConnectionHolder holder = new DruidConnectionHolder(this, pyConnectInfo);connections[poolingCount++] = holder;} catch (SQLException ex) {LOG.error("init datasource error, url: " + this.getUrl(), ex);if (initExceptionThrow) {connectError = ex;break;} else {Thread.sleep(3000);}}}if (poolingCount > 0) {poolingPeak = poolingCount;poolingPeakTime = System.currentTimeMillis();}}// 一些辅助性，日志啥的初始化操作createAndLogThread();createAndStartCreatorThread();createAndStartDestroyThread();initedLatch.await();init = true;initedTime = new Date();registerMbean();if (connectError != null && poolingCount == 0) {throw connectError;}// 前面使用的是initialSize 初始连接数// 这个使用的是 keepAlive 看着意思是空闲连接数if (keepAlive) {// async fill to minIdleif (createScheduler != null) {for (int i = 0; i < minIdle; ++i) {submitCreateTask(true);}} else {this.emptySignal();}}} catch (SQLException e) {LOG.error("{dataSource-" + this.getID() + "} init error", e);throw e;} catch (InterruptedException e) {throw new SQLException(e.getMessage(), e);} catch (RuntimeException e){LOG.error("{dataSource-" + this.getID() + "} init error", e);throw e;} catch (Error e){LOG.error("{dataSource-" + this.getID() + "} init error", e);throw e;} finally {inited = true;lock.unlock();if (init && LOG.isInfoEnabled()) {String msg = "{dataSource-" + this.getID();if (this.name != null && !this.name.isEmpty()) {msg += ",";msg += this.name;}msg += "} inited";LOG.info(msg);}}}