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From sjcorbett <>
Subject [GitHub] incubator-brooklyn pull request: Adds boolean ConfigKey.isNonNull(...
Date Wed, 26 Nov 2014 18:05:54 GMT
Github user sjcorbett commented on the pull request:
    I'd argue it does simplify the code. It is not only preventing `set(null)`, it also provides
a standard way to catch missing configuration when an entity is created. Currently, to check
a ConfigKey was set you have to write something like:
    public void init() {
        checkNotNull(getConfig(MY_CONFIG), "Entity requires a value for MY_CONFIG");
    This splits the statement of intent that a value for `MY_CONFIG` must be set when the
entity is created away from definition of the key. There is no feasible way for us to generate
documentation that indicates that `MY_CONFIG` must be set.
    With the change in this pull request we can replace the check in the `init` method by
defining the config key as:
    ConfigKey<Object> MY_CONFIG = ConfigKeys.newConfigKey(Object.class)
    Attempts to create entities missing mandatory configuration are automatically caught in
`InternalEntityFactory`. We can extend the jsgui to indicate required configuration when you're
adding an app or an entity (and even prevent submissions that are missing such values) or
are browsing the catalogue. We can also indicate required configuration in the catalogue documentation
on the Brooklyn website.
    The change is backwards compatible - all existing ConfigKeys remain nullable. The nulling-a-parents-key
case is valid. I envisage this being used selectively rather than left, right and centre.
    It should definitely be annotated `@Beta`.

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