src/main/java/org/apache/maven/artifact/resolver/conflict/OldestConflictResolver.java

package org.apache.maven.artifact.resolver.conflict;

/*
 * 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.artifact.resolver.ResolutionNode;
import org.apache.maven.artifact.versioning.ArtifactVersion;
import org.apache.maven.artifact.versioning.OverConstrainedVersionException;

/**
 * Resolves conflicting artifacts by always selecting the <em>oldest</em> declaration. Oldest is defined as the
 * declaration whose version is less according to <code>ArtifactVersion.compareTo</code>.
 * 
 * @author <a href="mailto:markhobson@gmail.com">Mark Hobson</a>
 * @version $Id$
 * @see ArtifactVersion#compareTo(Object)
 * @since 3.0
 */
public class OldestConflictResolver
    implements ConflictResolver
{
    // ConflictResolver methods -----------------------------------------------
    
    /*
     * @see org.apache.maven.artifact.resolver.conflict.ConflictResolver#resolveConflict(org.apache.maven.artifact.resolver.ResolutionNode,
     *      org.apache.maven.artifact.resolver.ResolutionNode)
     */
    public ResolutionNode resolveConflict( ResolutionNode node1, ResolutionNode node2 )
    {
        try
        {
            ArtifactVersion version1 = node1.getArtifact().getSelectedVersion();
            ArtifactVersion version2 = node2.getArtifact().getSelectedVersion();
            
            return version1.compareTo( version2 ) <= 0 ? node1 : node2;
        }
        catch (OverConstrainedVersionException exception)
        {
            // TODO: log message or throw exception?
            
            return null;
        }
    }
}