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@Cleanup

Automatic resource management: Call your close() methods safely with no hassle.

Overview

- You can use @Cleanup to ensure a given resource is automatically cleaned up before the code execution path exits your - current scope. You do this by annotating any local variable declaration with the @Cleanup annotation like so:
- @Cleanup InputStream in = new FileInputStream("some/file");
- As a result, at the end of the scope you're in, in.close() is called. This call is guaranteed to run by way of a - try/finally construct. Look at the example below to see how this works. -

- If the type of object you'd like to cleanup does not have a close() method, but some other no-argument method, you can - specify the name of this method like so:
- @Cleanup("dispose") org.eclipse.swt.widgets.CoolBar bar = new CoolBar(parent, 0);
- By default, the cleanup method is presumed to be close(). A cleanup method that takes 1 or more arguments cannot be called via - @Cleanup. -

With Lombok

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Vanilla Java

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Supported configuration keys:

lombok.cleanup.flagUsage = [warning | error] (default: not set): Lombok will flag any usage of @Cleanup as a warning or error if configured.

Small print

- In the finally block, the cleanup method is only called if the given resource is not null. However, if you use delombok - on the code, a call to lombok.Lombok.preventNullAnalysis(Object o) is inserted to prevent warnings if static code analysis could - determine that a null-check would not be needed. Compilation with lombok.jar on the classpath removes that method call, - so there is no runtime dependency. -

- If your code throws an exception, and the cleanup method call that is then triggered also throws an exception, then the original exception - is hidden by the exception thrown by the cleanup call. You should not rely on this 'feature'. Preferably, lombok would like to generate - code so that, if the main body has thrown an exception, any exception thrown by the close call is silently swallowed (but if the main body - exited in any other way, exceptions by the close call will not be swallowed). The authors of lombok do not currently know of a feasible way - to implement this scheme, but if java updates allow it, or we find a way, we'll fix it. -

- You do still need to handle any exception that the cleanup method can generate! -

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