The Maven enforcer plugin lets you control or enforce constraints in your build environment. These could be the Maven version, Java version, operating system parameters, and even user-defined rules.
The plugin defines two goals: enforce and displayInfo. The enforcer:enforce goal will execute all the defined rules against all the modules in a multi-module Maven project, while enforcer:displayInfo will display the project compliance details with respect to the standard rule set.
The maven-enforcer-plugin is not defined in the super POM and should be explicitly defined in your project POM file:
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.3.1</version>
<executions>
<execution>
<id>enforce-versions</id>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<requireMavenVersion>
<version>3.2.1</version>
</requireMavenVersion>
<requireJavaVersion>
<version>1.6</version>
</requireJavaVersion>
<requireOS>
<family>mac</family>
</requireOS>
</rules>
</configuration>
</execution>
</executions>
</plugin>
</plugins>The previous plugin configuration enforces the Maven version to be 3.2.1, the Java version to be 1.6, and the operating system to be in the Mac family.
The Apache Axis2 project uses the enforcer plugin to make sure that no application POM file defines Maven repositories. All the artifacts required by Axis2 are expected to be in the Maven central repository. The following configuration element is extracted from http://svn.apache.org/repos/asf/axis/axis2/java/core/trunk/modules/parent/pom.xml. Here, it bans all the repositories and plugin repositories, except snapshot repositories:
<plugin>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.1</version>
<executions>
<execution>
<phase>validate</phase>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<requireNoRepositories>
<banRepositories>true</banRepositories>
<banPluginRepositories>true</banPluginRepositories>
<allowSnapshotRepositories>true</allowSnapshotRepositories>
<allowSnapshotPluginRepositories>true</allowSnapshotPluginRepositories>
</requireNoRepositories>
</rules>
</configuration>
</execution>
</executions>
</plugin>Note
In addition to the standard rule set ships with the enforcer plugin, you can also define your own rules. More details about how to write custom rules are available at http://maven.apache.org/enforcer/enforcer-api/writing-a-custom-rule.html.