java - 在 ThreadLocal 中包装 JDBC 连接单例

Question

在阅读第一部分后，我正在开发使用普通 JDBC 的小型 CRUD 应用程序，以及基于 Connection 枚举的单例的 Java Concurrency in Practice我只是喜欢 ThreadLocal 编写线程安全代码的方法，我的问题是:

在 ThreadLocal 中包装全局 JDBC 连接时被认为是一种好的做法？

Answer 1

When wrapping global JDBC connection in a ThreadLocal considered a good practice ?

很大程度上取决于细节。如果有大量线程，那么每个线程都将打开自己的连接，这可能会让人望而却步。然后，当线程处于 hibernate 状态时，您将拥有停滞不前的连接。

最好使用可重入的连接池。然后您可以重用已经打开但当前未使用的连接，但将连接数限制为同时工作所需的最少连接数。 Apache's DBCP是一个很好的例子，并且经过深思熟虑。

引用他们的文档:

Creating a new connection for each user can be time consuming (often requiring multiple seconds of clock time), in order to perform a database transaction that might take milliseconds. Opening a connection per user can be unfeasible in a publicly-hosted Internet application where the number of simultaneous users can be very large. Accordingly, developers often wish to share a "pool" of open connections between all of the application's current users. The number of users actually performing a request at any given time is usually a very small percentage of the total number of active users, and during request processing is the only time that a database connection is required.