oracle - 当 session 在没​​有连接的情况下打开和关闭时，Hibernate 查询停止

Question

我们有一个使用 Hibernate 查询 Oracle 数据库的 Grails 应用程序。

通过诸如 SQL Developer 之类的工具直接针对数据库运行一个相对简单的条件查询，最坏情况下只需要二十分之一秒，而现在则需要几分之一秒到 30 秒完成。

将 logSql 设置为 true 并确认生成的 SQL 是高性能的(解释计划成本约为 100，执行时间为 10-30 毫秒)，我们在通过将其日志记录级别设置为 TRACE 来更深入地了解 Hibernate 在做什么。

这是我们在标准输出中看到的:

******************** START HIBERNATE QUERY TRACE *****************
start time (millis): 1400772671767
2014-05-22 11:31:11,767 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - begin
2014-05-22 11:31:11,767 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - current autocommit status: true
2014-05-22 11:31:11,767 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - disabling autocommit
2014-05-22 11:31:11,767 [http-bio-8080-exec-5] TRACE jdbc.JDBCContext  - after transaction begin
2014-05-22 11:31:11,770 [http-bio-8080-exec-5] TRACE loader.Loader  - querySpaces is [REDACTED]
2014-05-22 11:31:11,770 [http-bio-8080-exec-5] TRACE loader.Loader  - transformer=org.hibernate.transform.RootEntityResultTransformer returnTypes=[ REDACTED ] returnClasses=[ class REDACTED ]
2014-05-22 11:31:11,770 [http-bio-8080-exec-5] DEBUG jdbc.AbstractBatcher  - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
2014-05-22 11:31:11,771 [http-bio-8080-exec-5] DEBUG hibernate.SQL  - select REDACTED
2014-05-22 11:31:11,771 [http-bio-8080-exec-5] TRACE jdbc.AbstractBatcher  - preparing statement
2014-05-22 11:31:11,771 [http-bio-8080-exec-5] TRACE sql.BasicBinder  - binding parameter [1] as REDACTED
2014-05-22 11:31:11,771 [http-bio-8080-exec-5] TRACE sql.BasicBinder  - binding parameter [2] as REDACTED
2014-05-22 11:31:11,772 [http-bio-8080-exec-5] TRACE sql.BasicBinder  - binding parameter [3] as REDACTED
2014-05-22 11:31:11,772 [http-bio-8080-exec-5] TRACE loader.Loader  - Bound [4] parameters total
2014-05-22 11:31:12,323 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564865835008
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564865839104
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564874059776
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564874059777
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:14,332 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:16,339 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564882284544
2014-05-22 11:31:16,339 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:16,339 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:16,339 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564882284545
2014-05-22 11:31:16,340 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:16,340 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:18,348 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564890513408
2014-05-22 11:31:18,348 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:18,348 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:18,348 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564890513409
2014-05-22 11:31:18,349 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:18,349 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:20,356 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564898738176
2014-05-22 11:31:20,356 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:20,356 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:20,356 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564898738177
2014-05-22 11:31:20,357 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:20,357 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564906958848
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564906962944
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:24,373 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564915191808
2014-05-22 11:31:24,373 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:24,373 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:24,373 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564915191809
2014-05-22 11:31:24,374 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:24,374 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564923408384
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564923408385
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564931633152
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564931633153
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:28,388 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:30,395 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564939857920
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564939862016
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:32,403 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564948082688
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564948086784
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:34,408 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564956295168
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564956299264
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564964519936
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564964519937
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:36,417 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:38,421 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564972732416
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564972736512
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:40,428 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564980953088
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564980957184
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:42,436 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564989177856
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564989181952
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:44,441 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564997390336
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564997394432
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:46,449 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737565005615104
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737565005619200
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737565013839872
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737565013843968
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:49,985 [http-bio-8080-exec-5] DEBUG jdbc.AbstractBatcher  - about to open ResultSet (open ResultSets: 0, globally: 0)
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE loader.Loader  - processing result set
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE loader.Loader  - done processing result set (0 rows)
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] DEBUG jdbc.AbstractBatcher  - about to close ResultSet (open ResultSets: 1, globally: 1)
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] DEBUG jdbc.AbstractBatcher  - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE jdbc.AbstractBatcher  - closing statement
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE loader.Loader  - total objects hydrated: 0
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] DEBUG engine.StatefulPersistenceContext  - initializing non-lazy collections
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE loader.Loader  - transformer=org.hibernate.transform.RootEntityResultTransformer returnTypes=[ REDACTED ] returnClasses=[ class REDACTED ]
2014-05-22 11:31:49,987 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - commit
2014-05-22 11:31:49,987 [http-bio-8080-exec-5] TRACE impl.SessionImpl  - automatically flushing session
2014-05-22 11:31:49,987 [http-bio-8080-exec-5] TRACE def.AbstractFlushingEventListener  - flushing session
2014-05-22 11:31:49,987 [http-bio-8080-exec-5] REDACTED
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE jdbc.ConnectionManager  - registering flush begin
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE jdbc.ConnectionManager  - registering flush end
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE def.AbstractFlushingEventListener  - post flush
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE jdbc.JDBCContext  - before transaction completion
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE impl.SessionImpl  - before transaction completion
2014-05-22 11:31:49,991 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - re-enabling autocommit
2014-05-22 11:31:49,991 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - committed JDBC Connection
2014-05-22 11:31:49,991 [http-bio-8080-exec-5] TRACE jdbc.JDBCContext  - after transaction completion
2014-05-22 11:31:49,991 [http-bio-8080-exec-5] DEBUG jdbc.ConnectionManager  - transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources!
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] TRACE impl.SessionImpl  - after transaction completion
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] DEBUG impl.SessionImpl  - disconnecting session
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] TRACE jdbc.ConnectionManager  - performing cleanup
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] DEBUG jdbc.ConnectionManager  - releasing JDBC connection [ (open PreparedStatements: 0, globally: 0) (open ResultSets: 0, globally: 0)]
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] TRACE jdbc.JDBCContext  - after transaction completion
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] DEBUG jdbc.ConnectionManager  - transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources!
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] TRACE impl.SessionImpl  - after transaction completion
end time (millis): 1400772709992
difference: 38.225 seconds
******************* END HIBERNATE QUERY TRACE ********************

让我提醒您注意什么引起了我们的注意 - 大约每 2 秒重复的六行 - opened session 然后 closing session 然后 connection已经为空，在一毫秒的跨度内完成了两次。

Hibernate 每隔 2 秒左右打开并立即关闭 2 个 session ？我的解释正确吗？什么情况下它会做这样的事情？

DataSource.groovy中的数据源配置是基本的:

dataSource_REDACTED {
        driverClassName = 'oracle.jdbc.OracleDriver'
        dialect = 'org.hibernate.dialect.Oracle10gDialect'
        url = 'jdbc:oracle:thin:@REDACTED:1521/REDACTED'
        username = 'REDACTED'
        password = 'REDACTED'
        pooled = true
        properties {
            maxActive = 20
            minIdle = 1
            initialSize = 10
            testOnBorrow = true
            testWhileIdle = true
            validationQuery = "SELECT 1 FROM DUAL"
        }
}

没有 properties{} 阻塞在那里，所以无论使用空闲超时等属性的默认值。

同一个文件中还有一个hibernate配置:

hibernate {
    cache.use_second_level_cache = true
    cache.use_query_cache = true
    cache.provider_class = 'net.sf.ehcache.hibernate.EhCacheProvider'
} 

正如我之前所说，我正在执行的条件查询非常简单:

withTransaction {
    List<MyAwesomeClass> awesomeThings = withCriteria {
        between("importantTime", startDate, endDate)
        eq("importantField", targetValue)
    }
 }

条件查询是从 Controller 直接调用的 Grails 域类中的方法运行的，而不是事务服务，因此我将其包装在 withTransaction 中。

总之，简而言之，这是怎么回事？为什么在某事(不确定是什么)发生并且查询实际执行之前， session 会如此​​困惑？尝试创建连接时是否与数据库本身的可用性有关？

Answer 1

这行引起了我的注意:

transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources! 
TRACE jdbc.JDBCContext  - after autocommit

根据 Hibernate docs :

ON_CLOSE - is essentially the legacy behavior described above. The Hibernate session obtains a connection when it first needs to perform some JDBC access and holds unto that connection until the session is closed.

on_close - says to use ConnectionReleaseMode.ON_CLOSE. This setting is left for backwards compatibility, but its use is highly discouraged.

JPA 确实允许您执行查询，即使您没有在事务中运行，但我不建议您使用此设置。

我总是将所有 Hibernate 代码包装在一个事务中，对于只读操作，我选择 readOnly=true 标志。

每个线程似乎连续打开和关闭两个 session ，如果那是因为您运行两个连续的查询，您可以通过在同一 session 中运行它们来优化它。

因为您打开和关闭 session 的速度如此之快，所以您也在打开和关闭 JDBC 连接，并且您的设置不包含任何连接池。除非您使用连接池，否则创建和销毁连接的成本将非常高。

查看我的 benchmark on how connection pooling可以显着提高您的应用程序性能。

所以:

1. 始终使用交易
2. 使用连接池