ddewaele / pedantic-pom-enforcers

One does not simply write a POM file

Pedantic POM Enforcers

- One does not simply write a POM file

Have you ever experienced symptoms like headaches, unfocused anger or a feeling of total resignation when looking at a Maven project where everybody adds and changes stuff just as they need? Do people call you a "POM-Nazi" if you show them how to setup proper and well organized projects?

If so, the Pedantic POM Enforcers are absolutely the thing you need!

What are the Pedantic POM Enforcers?

The Pedantic POM Enforcers consist of serveral Maven enforcer rules that help you keep your project setup consistent and organized. For example, the enforcer rules ensure that your POM files are organized in a well-defined manner, that your <modules>/<dependencyManagement>/<dependencies>/<pluginManagement> sections are sorted in a reasonable way and that version numbers, plugin configurations, etc. are defined only on places where it makes sense.

How to use the Pedantic POM Enforcers

The Pedantic POM Enforcers are available on Maven Central. So no further repository configuration is required.

To activate the enforcer rules, just declare them in the configuration of the maven-enforcer-plugin. The simplest way of doing this is using the CompoundPedanticEnforcer, which is able to aggregate all choosen enforcer rules. The compound enforcer is also more efficient than using the single enforcer rules separately.

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-enforcer-plugin</artifactId>
      <version>1.1</version>
      <configuration>
        <rules>
          <compound implementation="com.github.ferstl.maven.pomenforcers.CompoundPedanticEnforcer">
            <!-- Enforcers -->
            <enforcers>POM_SECTION_ORDER,MODULE_ORDER,DEPENDENCY_MANAGEMENT_ORDER,DEPENDENCY_ORDER,PLUGIN_MANAGEMENT_ORDER</enforcers>
          
            <!-- Further configuration of the declared enforcer rules -->
            ...
          </compound>
        </rules>
        <fail>true</fail>
      </configuration>
      <dependencies>
        <dependency>
          <groupId>com.github.ferstl</groupId>
          <artifactId>pedantic-pom-enforcers</artifactId>
          <version>1.0.0</version>
        </dependency>
      </dependencies>
    </plugin>
    ...
  </plugins>
</build>

Why comma-separated Strings?

You may wonder why comma-separated strings are used to configure the enforcer rules although the maven-enforcer-plugin supports structured configurations like

<!-- Note: This configuration is not valid for the Pedantic POM Enforcers! -->
<enforcers>
  <enforcer>POM_SECTION_ORDER</enforcer>
  <enforcer>MODULE_ORDER</enforcer>
  ...
</enforcers>

The reason is simple: The comma-separated strings can be defined as <properties> in a POM file. In case a submodule requires a different configuration, the properties can easily be overwritten in the submodule's POM. This allows to add or remove specific enforcer rules or to alter configuration values without redefining the whole plugin configuration.

Available Enforcer Rules

These are the currently available Pedantic POM Enforcers. The ID in parentheses is required by the CompoundPedanticEnforcer's configuration. For further details take a look at the Wiki.

Enforcer Rule	ID	Description
CompoundPedanticEnforcer	n/a	Used to aggregate several pedantic enforcer rules.
PedanticPomSectionOrderEnforcer	POM_SECTION_ORDER	This enforcer makes sure that the sections in your POM files are in a defined order.
PedanticModuleOrderEnforcer	MODULE_ORDER	This enforcer makes sure that your modules section is sorted alphabetically.
PedanticDependencyManagementOrderEnforcer	DEPENDENCY_MANAGEMENT_ORDER	This enforcer makes sure that all artifacts in your dependency management are ordered.
PedanticDependencyManagementLocationEnforcer	DEPENDENCY_MANAGEMENT_LOCATION	Enforces that only a well-defined set of POMs may declare plugin management.
PedanticDependencyOrderEnforcer	DEPENDENCY_ORDER	This enforcer makes sure that all artifacts in your dependencies section are ordered.
PedanticDependencyConfigurationEnforcer	DEPENDENCY_CONFIGURATION	This enforcer makes sure that dependency versions and exclusions are declared in the <dependencyManagement> section.
PedanticDependencyScopeEnforcer	DEPENDENCY_SCOPE	Enforces that the configured dependencies have to be defined within a specific scope.
PedanticPluginManagementOrderEnforcer	PLUGIN_MANAGEMENT_ORDER	This enforcer makes sure that all plugins in your plugin management section are ordered.
PedanticPluginConfigurationEnforcer	PLUGIN_CONFIGURATION	Enforces that plugin versions, configurations and dependencies are defined in the <pluginManagement> section.
PedanticPluginManagementLocationEnforcer	PLUGIN_MANAGEMENT_LOCATION	Enforces that only a well-defined set of POMs may declare plugin management.