java MySQL 连接器/JDBC 线程安全吗？
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Is MySQL Connector/JDBC thread safe?
提问by Emil H
Is the standard MySQL JDBC driver thread-safe? Specifically I want to use a single connection across all threads, but each statement will only be used in a single thread. Are there certain scenarios that are safe and others that aren't? What's your experience here?
标准的 MySQL JDBC 驱动程序线程安全吗？具体来说，我想在所有线程中使用单个连接，但每个语句只会在单个线程中使用。是否有某些情况是安全的，而另一些则不安全？你在这里有什么体验？
采纳答案by ChssPly76
Transactions are started / committed per connection. Unless you're doing some very specific stuff (I can't really think of an example where that would be justified to be honest), you're better off with a connection pool and connection per thread.
每个连接启动/提交事务。除非你正在做一些非常具体的事情（我真的想不出一个诚实的例子），你最好使用连接池和每个线程的连接。
回答by ChssPly76
If autocommit = 1, then it is very feasible to have multiple threads share the same connection, provided the access to the connection is synchronized. If autocommit = 0, you will have to control access to the connection via some sort of mutex until the commit happens.
如果 autocommit = 1，那么多个线程共享同一个连接是非常可行的，前提是对连接的访问是同步的。如果 autocommit = 0，您将必须通过某种互斥锁控制对连接的访问，直到提交发生。
Unless you absolutely are limited in the amount of connections your application can have, a connection pool may be a more viable alternative.
除非您的应用程序可以拥有的连接数量绝对受到限制，否则连接池可能是更可行的替代方案。
回答by Alex
Based on my recent experience, Connectionobject is not thread safe in Connector/J 5.1.33.
根据我最近的经验，Connection对象在 Connector/J 5.1.33 中不是线程安全的。
I've ran into a deadlock situation described in bug 67760. Not sure if it is a bug, but one reasonable advice from the discussion was:
我遇到了错误 67760 中描述的死锁情况。不确定这是否是一个错误，但讨论中的一个合理建议是：
[12 Dec 2012 20:33] Todd Farmer
Please do not use a single Connection object across multiple threads without proper synchronization. Connector/J - and more importantly, the MySQL client-server protocol - does not allow for concurrent operations using the same Connection object. If a Connection object must be shared across threads, it is the responsibility of the application code author to ensure operations are properly serialized.
[2012 年 12 月 12 日 20:33] 托德·法默
请不要在没有适当同步的情况下跨多个线程使用单个 Connection 对象。Connector/J - 更重要的是，MySQL 客户端-服务器协议 - 不允许使用相同的 Connection 对象进行并发操作。如果必须跨线程共享 Connection 对象，则应用程序代码作者有责任确保操作正确序列化。
