BasicDataSource 配置引數

這些配置均在dbcp原始碼的BasicDataSource類的createPoolableConnectionFactory方法中使用和初始化。具體程式碼如下：

protected PoolableConnectionFactory createPoolableConnectionFactory(final ConnectionFactory driverConnectionFactory)
        throws SQLException {
    PoolableConnectionFactory connectionFactory = null;
    try {
        connectionFactory = new PoolableConnectionFactory(driverConnectionFactory,
                ObjectNameWrapper.unwrap(registeredJmxObjectName));
        connectionFactory.setValidationQuery(validationQuery);
        connectionFactory.setValidationQueryTimeout(validationQueryTimeoutSeconds);
        connectionFactory.setConnectionInitSql(connectionInitSqls);
        connectionFactory.setDefaultReadOnly(defaultReadOnly);
        connectionFactory.setDefaultAutoCommit(defaultAutoCommit);
        connectionFactory.setDefaultTransactionIsolation(defaultTransactionIsolation);
        connectionFactory.setDefaultCatalog(defaultCatalog);
        connectionFactory.setCacheState(cacheState);
        connectionFactory.setPoolStatements(poolPreparedStatements);
        connectionFactory.setMaxOpenPreparedStatements(maxOpenPreparedStatements);
        connectionFactory.setMaxConnLifetimeMillis(maxConnLifetimeMillis);
        connectionFactory.setRollbackOnReturn(getRollbackOnReturn());
        connectionFactory.setEnableAutoCommitOnReturn(getEnableAutoCommitOnReturn());
        connectionFactory.setDefaultQueryTimeout(getDefaultQueryTimeout());
        connectionFactory.setFastFailValidation(fastFailValidation);
        connectionFactory.setDisconnectionSqlCodes(disconnectionSqlCodes);
        validateConnectionFactory(connectionFactory);
    } catch (final RuntimeException e) {
        throw e;
    } catch (final Exception e) {
        throw new SQLException("Cannot create PoolableConnectionFactory (" + e.getMessage() + ")", e);
    }
    return connectionFactory;
}

接下來就是對這些配置的說明：

連線配置

提交屬性

連線屬性

注意⚠️：如果maxIdle設定的太小，當應用的負載比較高時，連線數會很快的超過maxIdle，但是應用使用完以後會立即被回收，但是此時應用負載依然很高，應用會再此申請連線，這時候連線數️會超過maxIdle，但是會永遠小於maxTotal，出現這種情況會連線會一直被建立然後銷燬，來來回回往往復復，連線數就會在maxIdle上下來回震盪。針對負載比較高的應用，最好設定maxIdle接近於maxTotal，例如設定的數量為maxTotal-1甚至等於maxTotal，或者無限制。

連線檢測

連線移除