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Posted to commits@maven.apache.org by rf...@apache.org on 2021/05/21 13:41:44 UTC
[maven-enforcer] 01/01: [MENFORCER-384] Introduce Maven Enforcer
Extension
This is an automated email from the ASF dual-hosted git repository.
rfscholte pushed a commit to branch MENFORCER-384
in repository https://gitbox.apache.org/repos/asf/maven-enforcer.git
commit a6cf1a910997bb91fc0c6304387bcb3e2ea11598
Author: rfscholte <rf...@apache.org>
AuthorDate: Fri May 21 15:41:28 2021 +0200
[MENFORCER-384] Introduce Maven Enforcer Extension
---
maven-enforcer-extension/pom.xml | 124 +++++++++++++++
maven-enforcer-extension/src/it/mrm/settings.xml | 73 +++++++++
.../projects/defaults/.mvn/enforcer-extension.xml | 42 +++++
.../src/it/projects/defaults/.mvn/extensions.xml | 28 ++++
.../src/it/projects/defaults/pom.xml | 29 ++++
.../src/it/projects/invoker.properties | 19 +++
.../extensions/enforcer/EnforceExtension.java | 176 +++++++++++++++++++++
maven-enforcer-extension/src/site/apt/index.apt | 46 ++++++
.../src/site/markdown/usage.md.vm | 54 +++++++
maven-enforcer-extension/src/site/site.xml | 34 ++++
pom.xml | 1 +
11 files changed, 626 insertions(+)
diff --git a/maven-enforcer-extension/pom.xml b/maven-enforcer-extension/pom.xml
new file mode 100644
index 0000000..354fbed
--- /dev/null
+++ b/maven-enforcer-extension/pom.xml
@@ -0,0 +1,124 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+ <parent>
+ <groupId>org.apache.maven.enforcer</groupId>
+ <artifactId>enforcer</artifactId>
+ <version>3.0.0-M4-SNAPSHOT</version>
+ </parent>
+ <groupId>org.apache.maven.extensions</groupId>
+ <artifactId>maven-enforcer-extension</artifactId>
+
+ <build>
+ <plugins>
+ <plugin>
+ <groupId>org.eclipse.sisu</groupId>
+ <artifactId>sisu-maven-plugin</artifactId>
+ <executions>
+ <execution>
+ <id>index-project</id>
+ <goals>
+ <goal>main-index</goal>
+ </goals>
+ </execution>
+ </executions>
+ </plugin>
+ </plugins>
+ </build>
+
+ <dependencies>
+ <dependency>
+ <groupId>org.apache.maven</groupId>
+ <artifactId>maven-core</artifactId>
+ <scope>provided</scope>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.maven.plugin-tools</groupId>
+ <artifactId>maven-plugin-annotations</artifactId>
+ <scope>provided</scope>
+ </dependency>
+ </dependencies>
+
+ <profiles>
+ <profile>
+ <id>run-its</id>
+ <properties>
+ <maven.it.failure.ignore>false</maven.it.failure.ignore>
+ </properties>
+ <build>
+ <plugins>
+ <plugin>
+ <groupId>org.apache.maven.plugins</groupId>
+ <artifactId>maven-invoker-plugin</artifactId>
+ <version>3.2.2</version>
+ <configuration>
+ <showErrors>true</showErrors>
+ <projectsDirectory>src/it/projects</projectsDirectory>
+ <cloneProjectsTo>${project.build.directory}/it</cloneProjectsTo>
+ <preBuildHookScript>setup</preBuildHookScript>
+ <postBuildHookScript>verify</postBuildHookScript>
+ <localRepositoryPath>${project.build.directory}/local-repo</localRepositoryPath>
+ <settingsFile>src/it/mrm/settings.xml</settingsFile>
+ <ignoreFailures>${maven.it.failure.ignore}</ignoreFailures>
+ <goals>
+ <goal>validate</goal>
+ </goals>
+ </configuration>
+ <executions>
+ <execution>
+ <id>integration-test</id>
+ <goals>
+ <goal>install</goal>
+ <goal>run</goal>
+ </goals>
+ </execution>
+ </executions>
+ </plugin>
+ <plugin>
+ <groupId>org.codehaus.mojo</groupId>
+ <artifactId>mrm-maven-plugin</artifactId>
+ <version>1.2.0</version>
+ <executions>
+ <execution>
+ <goals>
+ <goal>start</goal>
+ <goal>stop</goal>
+ </goals>
+ </execution>
+ </executions>
+ <configuration>
+ <propertyName>repository.proxy.url</propertyName>
+ <repositories>
+ <mockRepo>
+ <source>src/it/mrm/repository</source>
+ </mockRepo>
+ <proxyRepo />
+ </repositories>
+ </configuration>
+ </plugin>
+ </plugins>
+ </build>
+ </profile>
+ </profiles>
+</project>
\ No newline at end of file
diff --git a/maven-enforcer-extension/src/it/mrm/settings.xml b/maven-enforcer-extension/src/it/mrm/settings.xml
new file mode 100644
index 0000000..80734c5
--- /dev/null
+++ b/maven-enforcer-extension/src/it/mrm/settings.xml
@@ -0,0 +1,73 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+-->
+<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
+ http://maven.apache.org/xsd/settings-1.0.0.xsd">
+ <mirrors>
+ <mirror>
+ <id>mrm-maven-plugin</id>
+ <name>Mock Repository Manager</name>
+ <url>@repository.proxy.url@</url>
+ <mirrorOf>*</mirrorOf>
+ </mirror>
+ </mirrors>
+ <profiles>
+ <profile>
+ <id>it-repo</id>
+ <repositories>
+ <repository>
+ <id>snapshots</id>
+ <url>@repository.proxy.url@</url>
+ <releases>
+ <enabled>true</enabled>
+ <checksumPolicy>ignore</checksumPolicy>
+ <updatePolicy>never</updatePolicy>
+ </releases>
+ <snapshots>
+ <enabled>true</enabled>
+ <checksumPolicy>ignore</checksumPolicy>
+ <updatePolicy>always</updatePolicy>
+ </snapshots>
+ </repository>
+ </repositories>
+ <pluginRepositories>
+ <pluginRepository>
+ <id>snapshots</id>
+ <url>@repository.proxy.url@</url>
+ <releases>
+ <enabled>true</enabled>
+ <checksumPolicy>ignore</checksumPolicy>
+ <updatePolicy>never</updatePolicy>
+ </releases>
+ <snapshots>
+ <enabled>true</enabled>
+ <checksumPolicy>ignore</checksumPolicy>
+ <updatePolicy>always</updatePolicy>
+ </snapshots>
+ </pluginRepository>
+ </pluginRepositories>
+ </profile>
+ </profiles>
+ <activeProfiles>
+ <activeProfile>it-repo</activeProfile>
+ </activeProfiles>
+</settings>
\ No newline at end of file
diff --git a/maven-enforcer-extension/src/it/projects/defaults/.mvn/enforcer-extension.xml b/maven-enforcer-extension/src/it/projects/defaults/.mvn/enforcer-extension.xml
new file mode 100644
index 0000000..8e86524
--- /dev/null
+++ b/maven-enforcer-extension/src/it/projects/defaults/.mvn/enforcer-extension.xml
@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+<extension>
+ <executions>
+ <!-- defaults -->
+ <execution>
+ <configuration>
+ <rules>
+ <AlwaysPass />
+ </rules>
+ </configuration>
+ </execution>
+ <!-- configured -->
+ <execution>
+ <id>custom-id</id>
+ <phase>process-classes</phase>
+ <configuration>
+ <rules>
+ <AlwaysFail/>
+ </rules>
+ </configuration>
+ </execution>
+ </executions>
+</extension>
\ No newline at end of file
diff --git a/maven-enforcer-extension/src/it/projects/defaults/.mvn/extensions.xml b/maven-enforcer-extension/src/it/projects/defaults/.mvn/extensions.xml
new file mode 100644
index 0000000..da62f81
--- /dev/null
+++ b/maven-enforcer-extension/src/it/projects/defaults/.mvn/extensions.xml
@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+-->
+<extensions xmlns="http://maven.apache.org/EXTENSIONS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/EXTENSIONS/1.0.0 http://maven.apache.org/xsd/core-extensions-1.0.0.xsd">
+ <extension>
+ <groupId>org.apache.maven.extensions</groupId>
+ <artifactId>maven-enforcer-extension</artifactId>
+ <version>@project.version@</version>
+ </extension>
+</extensions>
\ No newline at end of file
diff --git a/maven-enforcer-extension/src/it/projects/defaults/pom.xml b/maven-enforcer-extension/src/it/projects/defaults/pom.xml
new file mode 100644
index 0000000..2c4a137
--- /dev/null
+++ b/maven-enforcer-extension/src/it/projects/defaults/pom.xml
@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<project>
+ <modelVersion>4.0.0</modelVersion>
+
+ <groupId>org.apache.maven.its.enforcer</groupId>
+ <artifactId>test</artifactId>
+ <version>1.0</version>
+
+</project>
diff --git a/maven-enforcer-extension/src/it/projects/invoker.properties b/maven-enforcer-extension/src/it/projects/invoker.properties
new file mode 100644
index 0000000..9bbbd74
--- /dev/null
+++ b/maven-enforcer-extension/src/it/projects/invoker.properties
@@ -0,0 +1,19 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+invoker.goals.1 = validate
+invoker.goals.2 = verify
+invoker.buildResult.2 = failure
diff --git a/maven-enforcer-extension/src/main/java/org/apache/maven/extensions/enforcer/EnforceExtension.java b/maven-enforcer-extension/src/main/java/org/apache/maven/extensions/enforcer/EnforceExtension.java
new file mode 100644
index 0000000..b5aff43
--- /dev/null
+++ b/maven-enforcer-extension/src/main/java/org/apache/maven/extensions/enforcer/EnforceExtension.java
@@ -0,0 +1,176 @@
+package org.apache.maven.extensions.enforcer;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Properties;
+
+import javax.inject.Named;
+
+import org.apache.maven.AbstractMavenLifecycleParticipant;
+import org.apache.maven.MavenExecutionException;
+import org.apache.maven.execution.MavenSession;
+import org.apache.maven.model.Build;
+import org.apache.maven.model.Plugin;
+import org.apache.maven.model.PluginExecution;
+import org.apache.maven.project.MavenProject;
+import org.codehaus.plexus.util.xml.Xpp3Dom;
+import org.codehaus.plexus.util.xml.Xpp3DomBuilder;
+import org.codehaus.plexus.util.xml.pull.XmlPullParserException;
+
+/**
+ * Extends every MavenProject with the maven-enforcer-plugin, adding executions as defined in
+ * <code>.mvn/enforcer-extension.xml</code>
+ *
+ * @since 3.0.0
+ */
+@Named( "enforcer" )
+public class EnforceExtension extends AbstractMavenLifecycleParticipant
+{
+ private static final String ENFORCER_EXTENSION_XML = ".mvn/enforcer-extension.xml";
+
+ private static final String POM_PROPERTIES =
+ "/META-INF/maven/org.apache.maven.extensions/maven-enforcer-extension/pom.properties";
+
+ @Override
+ public void afterProjectsRead( MavenSession session )
+ throws MavenExecutionException
+ {
+ Xpp3Dom configuration;
+ Path config = Paths.get( session.getExecutionRootDirectory(), ENFORCER_EXTENSION_XML );
+ if ( Files.isRegularFile( config ) )
+ {
+ try ( Reader reader = Files.newBufferedReader( config, StandardCharsets.UTF_8 ) )
+ {
+ configuration = Xpp3DomBuilder.build( reader );
+ }
+ catch ( XmlPullParserException | IOException e )
+ {
+ throw new MavenExecutionException( "Failed to read " + ENFORCER_EXTENSION_XML, e );
+ }
+ }
+ else
+ {
+ return;
+ }
+
+ List<PluginExecution> executions = null;
+ Xpp3Dom executionsDom = configuration.getChild( "executions" );
+ if ( executionsDom != null )
+ {
+ executions = new ArrayList<>();
+ for ( Xpp3Dom executionDom : executionsDom.getChildren( "execution" ) )
+ {
+ executions.add( getPluginExecution( executionDom ) );
+
+ }
+ }
+
+ if ( executions == null )
+ {
+ return;
+ }
+
+ for ( MavenProject project : session.getProjects() )
+ {
+ Plugin enforcerPlugin = null;
+ for ( Plugin plugin : project.getBuildPlugins() )
+ {
+ if ( "maven-enforcer-plugin".equals( plugin.getArtifactId() )
+ && "org.apache.maven.plugins".equals( plugin.getGroupId() ) )
+ {
+ enforcerPlugin = plugin;
+ }
+ }
+
+ if ( enforcerPlugin == null )
+ {
+ enforcerPlugin = new Plugin();
+ enforcerPlugin.setGroupId( "org.apache.maven.plugins" );
+ enforcerPlugin.setArtifactId( "maven-enforcer-plugin" );
+
+ try ( InputStream is = EnforceExtension.class.getResourceAsStream( POM_PROPERTIES ) )
+ {
+ Properties properties = new Properties();
+ properties.load( is );
+ enforcerPlugin.setVersion( properties.getProperty( "version" ) );
+ }
+ catch ( IOException e )
+ {
+ // noop
+ }
+
+ if ( project.getBuildPlugins().isEmpty() )
+ {
+ Build build = project.getBuild();
+ if ( build == null )
+ {
+ build = new Build();
+ project.setBuild( build );
+ }
+ build.setPlugins( Collections.singletonList( enforcerPlugin ) );
+ }
+ else
+ {
+ List<Plugin> buildPlugins = new ArrayList<>( project.getBuildPlugins() );
+ buildPlugins.add( enforcerPlugin );
+ project.getBuild().setPlugins( buildPlugins );
+ }
+ }
+
+ for ( PluginExecution pe : executions )
+ {
+ enforcerPlugin.addExecution( pe );
+ }
+ }
+ }
+
+ private static PluginExecution getPluginExecution( Xpp3Dom execution )
+ {
+ PluginExecution pluginExecution = new PluginExecution();
+ pluginExecution.setId( get( execution, "id", "default-extension" ) );
+ pluginExecution.addGoal( "enforce" );
+ pluginExecution.setPhase( get( execution, "phase", "validate" ) );
+ // here we must use Mavens internal configuration implementation
+ pluginExecution.setConfiguration( execution.getChild( "configuration" ) );
+ return pluginExecution;
+ }
+
+ private static String get( Xpp3Dom elm, String name, String defaultValue )
+ {
+ if ( elm == null || elm.getChild( name ) == null )
+ {
+ return defaultValue;
+ }
+ else
+ {
+ return elm.getChild( name ).getValue();
+ }
+ }
+}
diff --git a/maven-enforcer-extension/src/site/apt/index.apt b/maven-enforcer-extension/src/site/apt/index.apt
new file mode 100644
index 0000000..1d00ac3
--- /dev/null
+++ b/maven-enforcer-extension/src/site/apt/index.apt
@@ -0,0 +1,46 @@
+~~ Licensed to the Apache Software Foundation (ASF) under one
+~~ or more contributor license agreements. See the NOTICE file
+~~ distributed with this work for additional information
+~~ regarding copyright ownership. The ASF licenses this file
+~~ to you under the Apache License, Version 2.0 (the
+~~ "License"); you may not use this file except in compliance
+~~ with the License. You may obtain a copy of the License at
+~~
+~~ http://www.apache.org/licenses/LICENSE-2.0
+~~
+~~ Unless required by applicable law or agreed to in writing,
+~~ software distributed under the License is distributed on an
+~~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+~~ KIND, either express or implied. See the License for the
+~~ specific language governing permissions and limitations
+~~ under the License.
+
+ ------
+ Introduction
+ ------
+ Robert Scholte
+ ------
+ May 2021
+ ------
+
+Maven Enforcer Extension - The Extended Loving Iron Fist of Maven\x99
+
+ The Enforcer Extension provides a way to globally define rules without making use of pom inheritence.
+ This way you don't have to adjust the pom.xml , but you can enforce a set of rules.
+
+* Usage
+
+ General instructions on how to use the Enforcer Plugin can be found on the {{{./usage.html}usage page}}.
+
+ In case you still have questions regarding the plugin's usage, please have a look at the {{{./faq.html}FAQ}} and feel
+ free to contact the {{{./mailing-lists.html}user mailing list}}. The posts to the mailing list are archived and could
+ already contain the answer to your question as part of an older thread. Hence, it is also worth browsing/searching
+ the {{{./mailing-lists.html}mail archive}}.
+
+ If you feel like the plugin is missing a feature or has a defect, you can fill a feature request or bug report in our
+ {{{./issue-management.html}issue tracker}}. When creating a new issue, please provide a comprehensive description of your
+ concern. Especially for fixing bugs it is crucial that the developers can reproduce your problem. For this reason,
+ entire debug logs, POMs or most preferably little demo projects attached to the issue are very much appreciated.
+ Of course, patches are welcome, too. Contributors can check out the project from our
+ {{{./scm.html}source repository}} and will find supplementary information in the
+ {{{/guides/development/guide-helping.html}guide to helping with Maven}}.
diff --git a/maven-enforcer-extension/src/site/markdown/usage.md.vm b/maven-enforcer-extension/src/site/markdown/usage.md.vm
new file mode 100644
index 0000000..a9a4ec9
--- /dev/null
+++ b/maven-enforcer-extension/src/site/markdown/usage.md.vm
@@ -0,0 +1,54 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+Usage
+=====
+
+To use the maven-enforcer-extension, you must register the extension and configuration.
+
+Maven Extension
+---------------
+
+You have 2 ways to use Maven extensions within your builds:
+
+* add `maven-enforcer-extension-${project.version}.jar` in `${maven.home}/lib/ext` (no extra dependencies required),
+
+* (since Maven 3.3.1) configure your extension in [.mvn/extensions.xml](https://maven.apache.org/ref/current/maven-embedder/core-extensions.html).
+
+There is actually a third way: add the extension to the `pom.xml`, but in that case it makes more sense to use the [maven-enforcer-plugin](../maven-enforcer-plugin/) instead.
+
+Enforcer Extension
+------------------
+
+The `.mvn/enforcer-extension.xml` in the root of your Maven project is where you define your rules.
+It's content is similar to an execution-block of the maven-enforcer-plugin
+
+```xml
+<extension>
+ <executions>
+ <execution>
+ <id/> <!-- default: default-extension -->
+ <phase/> <!-- default: validate -->
+ <configuration> <!-- see Plugin Configuration -->
+ <rules/>
+ </configuration>
+ </execution>
+ </executions>
+</extension>
+```
diff --git a/maven-enforcer-extension/src/site/site.xml b/maven-enforcer-extension/src/site/site.xml
new file mode 100644
index 0000000..3929b21
--- /dev/null
+++ b/maven-enforcer-extension/src/site/site.xml
@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<project xmlns="http://maven.apache.org/DECORATION/1.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/DECORATION/1.0.0 http://maven.apache.org/xsd/decoration-1.0.0.xsd"
+ name="Maven Enforcer plugin">
+ <body>
+ <menu name="Overview">
+ <item name="Introduction" href="index.html"/>
+ <item name="Usage" href="usage.html"/>
+ <!-- According to https://issues.apache.org/jira/browse/MNGSITE-152 -->
+ <item name="License" href="http://www.apache.org/licenses/"/>
+ <item name="Download" href="../download.html"/>
+ </menu>
+ </body>
+</project>
diff --git a/pom.xml b/pom.xml
index 6902e5c..d98ac64 100644
--- a/pom.xml
+++ b/pom.xml
@@ -40,6 +40,7 @@
<module>enforcer-api</module>
<module>enforcer-rules</module>
<module>maven-enforcer-plugin</module>
+ <module>maven-enforcer-extension</module>
</modules>
<scm>