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

package org.apache.maven.enforcer.rule;

/*
 * 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 org.apache.maven.ProjectDependenciesResolver;
import org.apache.maven.enforcer.rule.api.EnforcerRule;
import org.apache.maven.enforcer.rule.api.EnforcerRuleException;
import org.apache.maven.enforcer.rule.api.EnforcerRuleHelper;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.plugin.logging.Log;
import org.apache.maven.project.MavenProject;
import org.codehaus.plexus.component.configurator.expression.ExpressionEvaluationException;
import org.codehaus.plexus.component.repository.exception.ComponentLookupException;

/**
 * @author <a href="mailto:brianf@apache.org">Brian Fox</a>
 * @author <a href="mailto:belingueres@gmail.com">Gabriel Belingueres</a>
 */
public class MyCustomRule
    implements EnforcerRule
{
    /**
     * Simple param. This rule fails if the value is true.
     */
    private boolean shouldIfail = false;

    public void execute( EnforcerRuleHelper helper )
        throws EnforcerRuleException
    {
        Log log = helper.getLog();

        try
        {
            // get the various expressions out of the helper.
            MavenProject project = (MavenProject) helper.evaluate( "${project}" );
            MavenSession session = (MavenSession) helper.evaluate( "${session}" );
            String target = (String) helper.evaluate( "${project.build.directory}" );
            String artifactId = (String) helper.evaluate( "${project.artifactId}" );
            String mavenVersion = (String) helper.evaluate( "${maven.version}" );

            // retrieve any component out of the session directly
            ProjectDependenciesResolver resolver = helper.getComponent( ProjectDependenciesResolver.class );

            log.info( "Retrieved Target Folder: " + target );
            log.info( "Retrieved ArtifactId: " +artifactId );
            log.info( "Retrieved Project: " + project );
            log.info( "Retrieved Maven version: " + mavenVersion );
            log.info( "Retrieved Session: " + session );
            log.info( "Retrieved Resolver: " + resolver );

            if ( this.shouldIfail )
            {
                throw new EnforcerRuleException( "Failing because my param said so." );
            }
        }
        catch ( ComponentLookupException e )
        {
            throw new EnforcerRuleException( "Unable to lookup a component " + e.getLocalizedMessage(), e );
        }
        catch ( ExpressionEvaluationException e )
        {
            throw new EnforcerRuleException( "Unable to lookup an expression " + e.getLocalizedMessage(), e );
        }
    }

    /**
     * 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.
     * 
     * The easiest way to do this is to return a hash computed from the values of your parameters.
     * 
     * If your rule is not cacheable, then the result here is not important, you may return anything.
     */
    public String getCacheId()
    {
        //no hash on boolean...only parameter so no hash is needed.
        return Boolean.toString( this.shouldIfail );
    }

    /**
     * This tells the system if the results are cacheable at all. Keep in mind that during
     * forked builds and other things, a given rule may be executed more than once for the same
     * project. This means that even things that change from project to project may still 
     * be cacheable in certain instances.
     */
    public boolean isCacheable()
    {
        return false;
    }

    /**
     * If the rule is cacheable and the same id is found in the cache, the stored results
     * are passed to this method to allow double checking of the results. Most of the time 
     * this can be done by generating unique ids, but sometimes the results of objects returned
     * by the helper need to be queried. You may for example, store certain objects in your rule
     * and then query them later.
     */
    public boolean isResultValid( EnforcerRule rule )
    {
        return false;
    }

    /**
     * Injects the value of the shouldIfail parameter into the custom rule.
     * 
     * @param shouldIfail set to true if you want the rule to fail. false to succeed.
     */
    public void setShouldIfail( boolean shouldIfail )
    {
        this.shouldIfail = shouldIfail;
    }

}