aether-api/src/main/java/org/eclipse/aether/resolution/ArtifactResolutionException.java

/*
 * 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.
 */
package org.eclipse.aether.resolution;

import java.util.Collections;
import java.util.List;

import org.eclipse.aether.RepositoryException;
import org.eclipse.aether.transfer.ArtifactNotFoundException;
import org.eclipse.aether.transfer.RepositoryOfflineException;

/**
 * Thrown in case of a unresolvable artifacts.
 */
public class ArtifactResolutionException
    extends RepositoryException
{

    private final transient List<ArtifactResult> results;

    /**
     * Creates a new exception with the specified results.
     * 
     * @param results The resolution results at the point the exception occurred, may be {@code null}.
     */
    public ArtifactResolutionException( List<ArtifactResult> results )
    {
        super( getMessage( results ), getCause( results ) );
        this.results = ( results != null ) ? results : Collections.<ArtifactResult> emptyList();
    }

    /**
     * Creates a new exception with the specified results and detail message.
     * 
     * @param results The resolution results at the point the exception occurred, may be {@code null}.
     * @param message The detail message, may be {@code null}.
     */
    public ArtifactResolutionException( List<ArtifactResult> results, String message )
    {
        super( message, getCause( results ) );
        this.results = ( results != null ) ? results : Collections.<ArtifactResult> emptyList();
    }

    /**
     * Creates a new exception with the specified results, detail message and cause.
     * 
     * @param results The resolution results at the point the exception occurred, may be {@code null}.
     * @param message The detail message, may be {@code null}.
     * @param cause The exception that caused this one, may be {@code null}.
     */
    public ArtifactResolutionException( List<ArtifactResult> results, String message, Throwable cause )
    {
        super( message, cause );
        this.results = ( results != null ) ? results : Collections.<ArtifactResult> emptyList();
    }

    /**
     * Gets the resolution results at the point the exception occurred. Despite being incomplete, callers might want to
     * use these results to fail gracefully and continue their operation with whatever interim data has been gathered.
     * 
     * @return The resolution results or {@code null} if unknown.
     */
    public List<ArtifactResult> getResults()
    {
        return results;
    }

    /**
     * Gets the first result from {@link #getResults()}. This is a convenience method for cases where callers know only
     * a single result/request is involved.
     * 
     * @return The (first) resolution result or {@code null} if none.
     */
    public ArtifactResult getResult()
    {
        return ( results != null && !results.isEmpty() ) ? results.get( 0 ) : null;
    }

    private static String getMessage( List<? extends ArtifactResult> results )
    {
        StringBuilder buffer = new StringBuilder( 256 );

        buffer.append( "The following artifacts could not be resolved: " );

        int unresolved = 0;

        String sep = "";
        for ( ArtifactResult result : results )
        {
            if ( !result.isResolved() )
            {
                unresolved++;

                buffer.append( sep );
                buffer.append( result.getRequest().getArtifact() );
                sep = ", ";
            }
        }

        Throwable cause = getCause( results );
        if ( cause != null )
        {
            if ( unresolved == 1 )
            {
                buffer.setLength( 0 );
                buffer.append( cause.getMessage() );
            }
            else
            {
                buffer.append( ": " ).append( cause.getMessage() );
            }
        }

        return buffer.toString();
    }

    private static Throwable getCause( List<? extends ArtifactResult> results )
    {
        for ( ArtifactResult result : results )
        {
            if ( !result.isResolved() )
            {
                Throwable notFound = null, offline = null;
                for ( Throwable t : result.getExceptions() )
                {
                    if ( t instanceof ArtifactNotFoundException )
                    {
                        if ( notFound == null )
                        {
                            notFound = t;
                        }
                        if ( offline == null && t.getCause() instanceof RepositoryOfflineException )
                        {
                            offline = t;
                        }
                    }
                    else
                    {
                        return t;
                    }

                }
                if ( offline != null )
                {
                    return offline;
                }
                if ( notFound != null )
                {
                    return notFound;
                }
            }
        }
        return null;
    }

}