[MENFORCER-455] New Enforcer API

enforcer-api/pom.xml

@@ -48,6 +48,29 @@
 
   <build>
     <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-resources-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>custom-rule</id>
+            <goals>
+              <goal>copy-resources</goal>
+            </goals>
+            <phase>pre-site</phase>
+            <configuration>
+              <outputDirectory>${project.build.directory}/custom-rule-sample</outputDirectory>
+              <escapeString>\</escapeString>
+              <resources>
+                <resource>
+                  <directory>src/custom-rule-sample</directory>
+                  <filtering>true</filtering>
+                </resource>
+              </resources>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-assembly-plugin</artifactId>

enforcer-api/src/custom-rule-sample/pom.xml

@@ -18,46 +18,65 @@
   * under the License. 
   *
 -->
+<!-- START SNIPPET: project-pom -->
 <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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+         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>
+
   <groupId>custom-rule</groupId>
   <artifactId>custom-rule-sample</artifactId>
-  <packaging>jar</packaging>
   <version>1.0</version>
+
   <name>My Custom Rule</name>
   <description>This is my custom rule.</description>
+
   <properties>
     <api.version>${project.version}</api.version>
-    <maven.version>3.0</maven.version>
+    <maven.version>${maven.version}</maven.version>
+    <!-- use JDK 1.8 at least -->
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <maven.compiler.target>1.8</maven.compiler.target>
   </properties>
+
   <dependencies>
     <dependency>
       <groupId>org.apache.maven.enforcer</groupId>
       <artifactId>enforcer-api</artifactId>
-      <version>${api.version}</version>
+      <version>\${api.version}</version>
       <scope>provided</scope>
     </dependency>
     <dependency>
       <groupId>org.apache.maven</groupId>
       <artifactId>maven-core</artifactId>
-      <version>${maven.version}</version>
+      <version>\${maven.version}</version>
       <scope>provided</scope>
     </dependency>
     <dependency>
-      <groupId>org.apache.maven</groupId>
-      <artifactId>maven-plugin-api</artifactId>
-      <version>${maven.version}</version>
+      <groupId>javax.inject</groupId>
+      <artifactId>javax.inject</artifactId>
+      <version>1</version>
       <scope>provided</scope>
     </dependency>
-    <dependency>
-      <groupId>junit</groupId>
-      <artifactId>junit</artifactId>
-      <version>4.13.2</version>
-      <scope>test</scope>
-    </dependency>
   </dependencies>
+
   <build>
+    <plugins>
+      <plugin>
+        <!-- generate index of project components -->
+        <groupId>org.eclipse.sisu</groupId>
+        <artifactId>sisu-maven-plugin</artifactId>
+        <version>0.9.0.M1</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>main-index</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
   </build>
-</project>
+
+</project>
+    <!-- END SNIPPET: project-pom -->

enforcer-api/src/custom-rule-sample/src/main/java/org/example/custom/rule/MyCustomRule.java

@@ -0,0 +1,103 @@
+/*
+ * 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.
+ */
+
+// START SNIPPET: rule-implementation
+package org.example.custom.rule;
+
+import javax.inject.Inject;
+import javax.inject.Named;
+
+import java.util.List;
+
+import org.apache.maven.enforcer.rule.api.AbstractEnforcerRule;
+import org.apache.maven.enforcer.rule.api.EnforcerRuleException;
+import org.apache.maven.execution.MavenSession;
+import org.apache.maven.project.MavenProject;
+import org.apache.maven.rtinfo.RuntimeInformation;
+
+/**
+ * Custom Enforcer Rule - example
+ */
+@Named("myCustomRule") // rule name - must start from lowercase character
+public class MyCustomRule extends AbstractEnforcerRule {
+
+    /**
+     * Simple param. This rule fails if the value is true.
+     */
+    private boolean shouldIfail = false;
+
+    /**
+     * Rule parameter as list of items.
+     */
+    private List<String> listParameters;
+
+    // Inject needed Maven components
+
+    @Inject
+    private MavenProject project;
+
+    @Inject
+    private MavenSession session;
+
+    @Inject
+    private RuntimeInformation runtimeInformation;
+
+    public void execute() throws EnforcerRuleException {
+
+        getLog().info("Retrieved Target Folder: " + project.getBuild().getDirectory());
+        getLog().info("Retrieved ArtifactId: " + project.getArtifactId());
+        getLog().info("Retrieved Project: " + project);
+        getLog().info("Retrieved Maven version: " + runtimeInformation.getMavenVersion());
+        getLog().info("Retrieved Session: " + session);
+        getLog().warnOrError("Parameter shouldIfail: " + shouldIfail);
+        getLog().info(() -> "Parameter listParameters: " + listParameters);
+
+        if (this.shouldIfail) {
+            throw new EnforcerRuleException("Failing because my param said so.");
+        }
+    }
+
+    /**
+     * If your rule is cacheable, you must return a unique id when parameters or conditions
+     * change that would cause the result to be different. Multiple cached results are stored
+     * based on their id.
+     * <p>
+     * The easiest way to do this is to return a hash computed from the values of your parameters.
+     * <p>
+     * If your rule is not cacheable, then you don't need to override this method or return null
+     */
+    @Override
+    public String getCacheId() {
+        //no hash on boolean...only parameter so no hash is needed.
+        return Boolean.toString(shouldIfail);
+    }
+
+    /**
+     * A good practice is provided toString method for Enforcer Rule.
+     * <p>
+     * Output is used in verbose Maven logs, can help during investigate problems.
+     *
+     * @return rule description
+     */
+    @Override
+    public String toString() {
+        return String.format("MyCustomRule[level=%s, shouldIfail=%b]", getLevel(), shouldIfail);
+    }
+}
+// END SNIPPET: rule-implementation