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https://issues.apache.org/jira/browse/MSHADE-205?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Karl Heinz Marbaise updated MSHADE-205:
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Fix Version/s: 2.4.2
> Better use of ClazzpathUnit for improved jar minimization
> ---------------------------------------------------------
>
> Key: MSHADE-205
> URL: https://issues.apache.org/jira/browse/MSHADE-205
> Project: Maven Shade Plugin
> Issue Type: Improvement
> Affects Versions: 2.4.1
> Reporter: Benoit Perrot
> Fix For: 2.4.2
>
>
> Minimizing an uber-jar consists in assessing the relevance of classes of all
> artifacts on which the project being processed depends: when a class is not
> identified as being used, it is simply removed from the final jar.
> To support implicit uses (e.g. dynamically loaded classes), it is possible to
> explicitly tell the maven-shade-plugin that a classes must be specifically
> included.
> The algorithm for assessing the relevance of these classes is roughly the
> following:
> {code}
> // All classes are initially considered as irrelevant
> for each artifact in dependencies:
> for each class in the set of irrelevant ones:
> if artifact contains class && class is specifically included:
> remove class from the set of irrelevant ones
> {code}
> Checking whether an artifact contains a class or not is done by invoking the
> {{getClazzes()}} method on {{org.vafer.jdependency}} {{ClazzpathUnit}}.
> Contrary to what its name suggests, this method is not as harmless as it
> seems: it actually builds a hash set and fills it up with the entire set of
> classes in a given jar _each time it is called_. (See ClazzpathUnit.java,
> line 36 at the time of writing)
> The instance of {{ClazzpathUnit}} is not modified during the iteration, so
> simply caching the result of this {{getClazzes()}} would avoid the creation
> and filling of the said set, and greatly increase the speed of the process.
> The improvement obviously depends on the number of artifacts used by the
> project being processed, and the number of classes inside them. We observed
> very significant gains on our industrial cases.
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