RFR: 7027: Avoid NPE for callers of TransformRegistry#getTransformData

[Marcus Hirt]

On Sun, 29 Nov 2020 19:27:48 GMT, Gunnar Morling <github.com+28612+gunnarmorling at openjdk.org> wrote:

> …) of no transform data exists
> 
> @thegreystone, @Josh-Matsuoka, et al., this fixes an NPE in the `Transformer` class if there is no metadata for the given class (we unconditionally try to iterate over the returned list). I noticed this while debugging something else, it seems this NPE gets swallowed elsewhere, but creating it over and over is costly of course.
> 
> I think never returning null from a collection method is a good practice anyways, so I've changed it accordingly. Could someone log an issue for this, so I can reference it? Thanks!

Changes requested by hirt (Lead).

agent/src/main/java/org/openjdk/jmc/agent/TransformRegistry.java line 2:

> 1: /*
> 2:  * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.

Update copyright year - 2018, 2020.

agent/src/test/java/org/openjdk/jmc/agent/test/TestDefaultTransformRegistry.java line 2:

> 1: /*
> 2:  * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.

Update copyright year - 2018, 2020.

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PR: https://git.openjdk.java.net/jmc/pull/169