Maven POM file best practices

Author: Vina Martin (Deactivated)

Plugins:

• Eliminate phase overrides OR be sure to provide proper documentation to explain why this override is necessary
• Jacoco overrides cause Maven warnings in most/all poms because the version is missing, evaluate a solution for this to clean up Maven warnings
• Consider moving plugins that may be used across downstream projects to ddf-parent's pluginManagement definition

Dependencies:

• Eliminate unused, redundant dependencies
• IntelliJ can help find duplicated dependencies in poms
• Evaluate dependencies that may have been copy-pasted and are not used
• Double check embed dependencies and import package
• Tighten dependency scopes when possible (6 scopes are available: compile, provided, runtime, test, system, import)
• Try to eliminate hardcoded version numbers when possible
• Try to eliminate overwritten version numbers OR be sure to provide proper documentation to explain version overrides
• Evaluate version inconsistencies and eliminate them using properties in the root pom OR dependency management when possible
• Remove usages of <dependencyManagement> at modules that do not have any sub modules (there is nothing to inherit these dependencies)
• Instead refactor these sections to simply be <dependencies> for any dependencies in <dependencyManagement> that this module needs
• Eliminate the anti-pattern of having submodules listed in <dependencyManagement>
• Refactor poms to explicitly use project.version for submodule dependencies and scope them properly
• Consider refactoring global dependencies into <dependencyManagement> (This can be difficult with the test dependencies)
• Consider eliminating dependencies in <dependencyManagement> that have a version property
• Since these dependencies already have a version property, simply refactor poms that inherit this dependency to explicitly use the version property instead of getting it from dependency management
• Refactor version properties that are duplicated in multiple submodules to live in the most appropriate parent pom
• Some submodules redefine the same version properties for their submodules; however, these properties should live in the appropriate parent pom so the versions do not diverge
• Remove dependency conflicts with dependency management

Style:

• Consistency in the layout of poms makes poms easy to read at a glance
• Consider refactoring poms where the dependencies stanza is at the end to have this stanza toward the top (under <packaging>) as it is in most poms in the code base
• Enforce consistent <name> styling throughout the code base
• Enforce documenting low/non-existent Jacoco coverage numbers
• (Going forward) Consider grouping dependencies and use comments to explain how/why they are used (especially for new dependencies and overrides)
• Always document confusing, weird, or hardcoded versions/dependencies/plugins to make it easier for other developers (ideally, we would not have any of these, though!)