if (inited) {            return;        }
        // bug fixed for dead lock, for issue #2980				// 利用类加载机制（天然线程安全，保证类只加载一次）实现驱动只注册一次        DruidDriver.getInstance();
        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());

if (this.jdbcUrl != null) {  this.jdbcUrl = this.jdbcUrl.trim();  initFromWrapDriverUrl();}

for (Filter filter : filters) {  filter.init(this);}

if (this.dbTypeName == null || this.dbTypeName.length() == 0) {  this.dbTypeName = JdbcUtils.getDbType(jdbcUrl, null);}
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");                }            }
            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");            }
            if (this.driverClass != null) {                this.driverClass = driverClass.trim();            }

// 通过spi机制加载用户自定义的过滤器initFromSPIServiceLoader();// 解析兼容部分特殊驱动resolveDriver();// oracle、db2、mysql特殊检查处理initCheck();// 初始化ExceptionSorter，initExceptionSorter();// 初始化ValidConnectionCheckerinitValidConnectionChecker();// 检查validationQuery参数配置是否完整validationQueryCheck();

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);

// 保存正常的连接，获取的数据库连接就是从这个数组获取connections = new DruidConnectionHolder[maxActive];// 保存需要丢弃的连接evictConnections = new DruidConnectionHolder[maxActive];// 保存需要进行keepAlive检查的连接keepAliveConnections = new DruidConnectionHolder[maxActive];

// 异步初始化连接if (createScheduler != null && asyncInit) {  for (int i = 0; i < initialSize; ++i) {    submitCreateTask(true);  }} else if (!asyncInit) {  // init connections  // 同步初始化连接  while (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);      }    }  }

// 打印线程池配置信息createAndLogThread();// 线程池扩容createAndStartCreatorThread();// 线程池缩容createAndStartDestroyThread();

if (keepAlive) {  // async fill to minIdle  if (createScheduler != null) {    for (int i = 0; i < minIdle; ++i) {      submitCreateTask(true);    }  } else {    this.emptySignal();  }}

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);}