Is shutdown-hook a good practice?

Question

I have a Service that makes requests via a RestClient.

What is the Java best practice between:

1. Opening and closing the connection every time I make a request
2. Opening the connection at class initialization and closing it in a ShutdownHook
3. Something I didn't think of

Answer 1

What is the Java best practice between

^{There are no "best practices". Please read and contemplate No Best Practices}

1. Opening and closing the connection every time I make a request

That's inefficient, especially if you are talking to an HTTPS endpoint.

Also, if you accidentally fail to close the connection, there is a potential that you will leak resources. It depends on how you open the connection.

2. Opening the connection at class initialization and closing it in a ShutdownHook.

OK but, don't need to close it in a shutdown hook. All of your application's outstanding network connections will be closed by the operating system when your application exits. Closing them explicitly is unnecessary.

3. Something I didn't think of ...

a. Open the connection once at the start (in class initialization, via a singleton, whatever) ... and don't bother to close it. (See above.)

b. Use an HTTP client or REST client library that can manage a connection pool. Especially if your application is multi-threaded, or if it talks to multiple HTTP or HTTPS endpoints.