Disadvantages of using threadlocal + filter to process connection pool

Currently, we recommend using servletfilter and threadlocal to process database connection pools or hibernate session factories. The principle is to use threadlocal to make the entire request process use the same connection instance or session instance!

The advantage is that

1. You do not need to fetch connections from the connection pool multiple times, and the performance is better (I am skeptical, because the consumption of retrieving connections from the connection pool is negligible)
2. the lazy load feature of hibernate can be used.
3.CodeMore brief and nice-looking
4. resources can be reliably released

However, I want to remind people using this method, first listing two disadvantages:

1. because the filter must be configured with URL-pattern, you must configure each page in your system that requires database connection separately (this will cause the web. the XML file is too large). Otherwise, some pages with static content will also occupy database connection resources.

Of course, this is also a solution, that is, to allocate resources on demand. When getconnection or getsession is called, allocate resources again.

2. when some pages require long-running operations, such as network operations and processing of large files, database operations only account for a very small part, in this case, the database connection resource is occupied for a long time, but no operation is performed. If this page has a very large number of concurrent accesses, the connection pool will be used up.

Although there are such shortcomings, we can still solve them through some workarounds! Here, I just want to remind developers not to simply considerModeThe model is important, but it is not something that can be used in all directions. Whether a system is good or not is determined by the user, not by the designer or developer, therefore, when considering a design method, we should compare the advantages and disadvantages and their direct consequences for users, and make a trade-off!