Java Spring - 事务只读
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Spring - Transaction Readonly
提问by AAK
Just wanted your expert opinions on declarative transaction management for Spring. Here is my setup:
只是想了解您对 Spring 声明式事务管理的专家意见。这是我的设置：
- DAO layer is plain old JDBC using Spring JdbcTemplate (No Hibernate etc)
- Service layer is POJO with declarative transactions as follows -
save*, readonly = false, rollback for Throwable
- DAO 层是使用 Spring JdbcTemplate（无 Hibernate 等）的普通旧 JDBC
- 服务层是具有声明性事务的 POJO，如下所示 -
save*, readonly = false, rollback for Throwable
Things work fine with above setup. However when I say get*, readonly = true, I see errors in my log file saying Database connection cannot be marked as readonly. This happens for all get* methods in service layer.
上面的设置一切正常。但是，当我说时get*, readonly = true，我在日志文件中看到错误说Database connection cannot be marked as readonly. 服务层中的所有 get* 方法都会发生这种情况。
Now my questions are:
现在我的问题是：
A. Do I have to set get*as readonly? All my get*methods are pure read DB operations. I do not wish to run them in any transaction context. How serious is the above error?
A. 我必须设置get*为只读吗？我所有的get*方法都是纯读数据库操作。我不希望在任何事务上下文中运行它们。上述错误有多严重？
B. When I remove the get*configuration, I do not see the errors. Morever, all my simple get*operations are performed without transactions. Is this the way to go?
B. 当我删除get*配置时，我没有看到错误。而且，我所有的简单get*操作都是在没有事务的情况下执行的。这是要走的路吗？
C. Why would anyone want to have transactional methods where readonly = true? Is there any practical significance of this configuration?
C. 为什么有人想要在何处使用事务方法readonly = true？这个配置有什么实际意义吗？
Thank you! As always, your responses are much appreciated!
谢谢！与往常一样，非常感谢您的回复！
采纳答案by Bozho
This posttells that the behaviour or the readOnlyflag is persistence-mechanism-dependent.
这篇文章告诉我们行为或readOnly标志是依赖于持久性机制的。
C.Yes, when using hibernate, it gives performance benefits by setting the flush mode to FLUSH_NEVER(as described in the linked post)
C.是的，当使用休眠时，它通过将刷新模式设置为FLUSH_NEVER（如链接帖子中所述）来提高性能
B.Yes, JDBC calls do not require a transaction (hibernate requires one), so removing the @Transactionalconfiguration trims all transaction management.
B.是的，JDBC 调用不需要事务（hibernate 需要一个），因此删除@Transactional配置会修剪所有事务管理。
A.I'd assume spring is calling connection.setReadOnly(true)but your JDBC driver doesn't support this
答：我假设 spring 正在调用，connection.setReadOnly(true)但您的 JDBC 驱动程序不支持此功能
The bottom-line is : don't use readonlytransactions with plain JDBC.
底线是：不要使用readonly带有普通 JDBC 的事务。
And another thing - transactions are supposed to span multiplequeries. Don't make your transactions too fine-grained. Make them a unit of work.
另一件事 - 交易应该跨越多个查询。不要让您的交易过于精细。使它们成为一个工作单元。
回答by matt b
A. Do I have to say get* as readonly? All my get* methods are pure read DB operations. I do not wish to run them in any transaction context. How serious is the above error?
A. 我必须说 get* 为只读吗？我所有的 get* 方法都是纯读取数据库操作。我不希望在任何事务上下文中运行它们。上述错误有多严重？
Actually, you probably still want to run all of your get()s in the context of a transaction, to make sure that you are getting consistent reads. If on the other hand, you don't care about this, you can set the transaction level accordingly.
实际上，您可能仍然希望get()在事务的上下文中运行所有s，以确保获得一致的读取。另一方面，如果您不关心这一点，则可以相应地设置事务级别。
C. Why would anyone want to have transactional methods where readonly = true? Is there any practical significance of this configuration?
C. 为什么有人想要 readonly = true 的事务方法？这个配置有什么实际意义吗？
- To help protect against errant writes within get()` methods
- For optimization purposes. Not only can Hibernate make use of this information, as Bozho mentioned, but some databases/JDBC drivers can also be make use of this info.
- 帮助防止 get()` 方法中的错误写入
- 出于优化目的。正如 Bozho 提到的，Hibernate 不仅可以利用这些信息，而且一些数据库/JDBC 驱动程序也可以利用这些信息。
