1. What I wish I Knew About

2. @aalmiray | andresalmiray.com
Andres
Almiray
Seasoned Sourceror
@ Oracle
Java Champion
Hackergarten
github.com/aalmiray

8. @aalmiray | andresalmiray.com
Override Project
Properties

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mvn -Dkey=value
• Properties may be defined
• In a <properties> block
• By plugins
• Property values defined on the command line have
precedence

10. DEMO

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mvn G:A:V:goal

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Invoke plugins on the go
• Any plugin may be applied using the long notation
G:A:V:goal, in other words
mvn com.github.ekryd.echo-maven-plugin:echo-maven-
plugin:1.2.0:echo -Decho.message="Hello World!"

13. DEMO

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Dependency
Resolution

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Dependencies
• Dependencies defined in a <dependencies> block are
known as direct dependencies.
• Dependencies brought by direct dependencies are known
as transitive dependencies.
• Maven resolves dependencies by locality
- direct in the current POM. Last found wins (closest).
- direct in the parent hierarchy.
- transitive in the hierarchy based on number of hops to
reach it. First found wins.

21. DEMO

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Semantic Versioning?
https://twitter.com/rfscholte/status/1243226856914063360

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Use the <dependencyManagement> block!

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http://maven.apache.org/enforcer/maven-enforcer-plugin/

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maven-enforcer-plugin
https://twitter.com/aalmiray/status/1243515942560313350

26. http://andresalmiray.com/maven-dependencies-pop-quiz-results

28. http://andresalmiray.com/maven-dependencies-pop-quiz-results

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Surviving Dependency Hell with Maven
https://saturnism.me/talk/surviving-dependency-hell-maven/

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mvn verify
• The Reactor knows how to build all requirements.
• The install goal should only be used when artifacts must
be published to the local repository.
• Invoking clean diminishes the reuse of intermediate
results -> defeats incremental builds.

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Broken Buildtools and Bad Behaviors;
The Maven Story by Robert Scholte
https://www.youtube.com/watch?v=2HyGxtsDf60

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mvn -am -pl

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Partial Execution
• Maven runs multi-project builds inside a Reactor.
• The Reactor executes goals for all projects.
• mvn -pl <paths> executes the given goals for all projects
in <paths>
• mvn -am -pl <paths> also executes for all prerequisites in
the Reactor

39. DEMO

41. @aalmiray | andresalmiray.com
Restrictions
• All invoked plugin goals must exist in every project!
• Define common plugins in parent POMs using a
combination of <pluginManagement> and <plugins>.
• You’d be forced to define dummy values for plugins in
some cases.

42. DEMO

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Aggregating POMs

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Aggregating POMs
• These POM files define a <modules> section.
• They are typically also parent POMs but they DO NOT
have to be!
• Also, values in <module> are paths, not project names.

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File Structure & POM

46. DEMO

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BOM Files

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BOM Definition

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BOM Consumption

50. DEMO

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Resources
• https://blogs.oracle.com/developers/mastering-maven-
the-series
• https://cguntur.me/2020/05/20/understanding-apache-
maven-the-series
• https://kordamp.org/kordamp-gradle-plugins

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The preceding is intended to outline our general product direction. It is intended for information
purposes only, and may not be incorporated into any contract. It is not a commitment to deliver
any material, code, or functionality, and should not be relied upon in making purchasing
decisions. The development, release, timing, and pricing of any features or functionality
described for Oracle’s products may change and remains at the sole discretion of Oracle
Corporation.
Statements in this presentation relating to Oracle’s future plans, expectations, beliefs,
intentions and prospects are “forward-looking statements” and are subject to material risks and
uncertainties. A detailed discussion of these factors and other risks that affect our business is
contained in Oracle’s Securities and Exchange Commission (SEC) filings, including our most
recent reports on Form 10-K and Form 10-Q under the heading “Risk Factors.” These filings
are available on the SEC’s website or on Oracle’s website at http://www.oracle.com/investor. All
information in this presentation is current as of September 2019 and Oracle undertakes no duty
to update any statement in light of new information or future events.
Safe Harbor Statement

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