org.eclipse.sisu.inject/src/org/eclipse/sisu/space/QualifierCache.java

/*******************************************************************************
 * Copyright (c) 2010, 2015 Sonatype, Inc.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Stuart McCulloch (Sonatype, Inc.) - initial API and implementation
 *******************************************************************************/
package org.eclipse.sisu.space;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import javax.inject.Qualifier;

/**
 * Caching {@link ClassVisitor} that maintains a map of known {@link Qualifier} annotations.
 */
final class QualifierCache
    implements ClassVisitor
{
    // ----------------------------------------------------------------------
    // Constants
    // ----------------------------------------------------------------------

    private static final String QUALIFIER_DESC = "Ljavax/inject/Qualifier;";

    private static final String NAMED_DESC = "Ljavax/inject/Named;";

    // ----------------------------------------------------------------------
    // Implementation fields
    // ----------------------------------------------------------------------

    private static final Map<String, Boolean> cachedResults = seedResults();

    private boolean isQualified;

    // ----------------------------------------------------------------------
    // Public methods
    // ----------------------------------------------------------------------

    public void enterClass( final int modifiers, final String name, final String _extends, final String[] _implements )
    {
        // no-op
    }

    public AnnotationVisitor visitAnnotation( final String desc )
    {
        isQualified |= QUALIFIER_DESC.equals( desc );
        return null;
    }

    public void leaveClass()
    {
        // no-op
    }

    // ----------------------------------------------------------------------
    // Local methods
    // ----------------------------------------------------------------------

    /**
     * Scans the given annotation type to see if it is marked with {@link Qualifier}.
     * 
     * @param space The class space
     * @param desc The annotation descriptor
     * @return {@code true} if the annotation is a qualifier; otherwise {@code false}
     */
    boolean qualify( final ClassSpace space, final String desc )
    {
        if ( NAMED_DESC.equals( desc ) )
        {
            return true;
        }
        final Boolean result = cachedResults.get( desc );
        if ( null == result )
        {
            isQualified = false;

            final String name = desc.substring( 1, desc.length() - 1 );
            SpaceScanner.accept( this, space.getResource( name + ".class" ) );
            cachedResults.put( desc, Boolean.valueOf( isQualified ) );

            return isQualified;
        }
        return result.booleanValue();
    }

    /**
     * Seeds the cache with the fully-qualified names listed in the 'sisu.qualifiers' system property.
     * 
     * @return Seeded results
     */
    private static Map<String, Boolean> seedResults()
    {
        final Map<String, Boolean> results = new ConcurrentHashMap<String, Boolean>( 32, 0.75f, 1 );
        try
        {
            final String qualifiers = System.getProperty( "sisu.qualifiers" );
            if ( qualifiers != null && qualifiers.length() > 0 )
            {
                final StringBuilder buf = new StringBuilder( "L" );
                for ( final String q : qualifiers.trim().split( "\\s*,\\s*" ) )
                {
                    buf.append( q.replace( '.', '/' ) ).append( ';' );
                    results.put( buf.toString(), Boolean.TRUE );
                    buf.setLength( 1 );
                }
            }
        }
        catch ( final RuntimeException e ) // NOPMD
        {
            // couldn't access system property, leave results unseeded
        }
        return results;
    }
}