maven-toolchain-builder/src/main/java/org/apache/maven/toolchain/merge/MavenToolchainMerger.java

package org.apache.maven.toolchain.merge;

/*
 * 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.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import org.apache.maven.toolchain.model.PersistedToolchains;
import org.apache.maven.toolchain.model.ToolchainModel;
import org.codehaus.plexus.util.xml.Xpp3Dom;

/**
 *
 * @author Robert Scholte
 * @since 3.2.4
 */
public class MavenToolchainMerger
{

    public void merge( PersistedToolchains dominant, PersistedToolchains recessive, String recessiveSourceLevel )
    {
        if ( dominant == null || recessive == null )
        {
            return;
        }

        recessive.setSourceLevel( recessiveSourceLevel );

        shallowMerge( dominant.getToolchains(), recessive.getToolchains(), recessiveSourceLevel );
    }

    private void shallowMerge( List<ToolchainModel> dominant, List<ToolchainModel> recessive,
                               String recessiveSourceLevel )
    {
        Map<Object, ToolchainModel> merged = new LinkedHashMap<>();

        for ( ToolchainModel dominantModel : dominant )
        {
            Object key = getToolchainModelKey( dominantModel );

            merged.put( key, dominantModel );
        }

        for ( ToolchainModel recessiveModel : recessive )
        {
            Object key = getToolchainModelKey( recessiveModel );

            ToolchainModel dominantModel = merged.get( key );
            if ( dominantModel == null )
            {
                recessiveModel.setSourceLevel( recessiveSourceLevel );
                dominant.add( recessiveModel );
            }
            else
            {
                mergeToolchainModelConfiguration( dominantModel, recessiveModel );
            }
        }
    }

    protected void mergeToolchainModelConfiguration( ToolchainModel target,
                                                    ToolchainModel source )
    {
        Xpp3Dom src = (Xpp3Dom) source.getConfiguration();
        if ( src != null )
        {
            Xpp3Dom tgt = (Xpp3Dom) target.getConfiguration();
            if ( tgt == null )
            {
                tgt = Xpp3Dom.mergeXpp3Dom( new Xpp3Dom( src ), tgt );
            }
            else
            {
                tgt = Xpp3Dom.mergeXpp3Dom( tgt, src );
            }
            target.setConfiguration( tgt );
        }
    }

    protected Object getToolchainModelKey( ToolchainModel model )
    {
        return model;
    }

}