DefaultQueryExecutorManager.java

/*
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.xwiki.query.internal;

import java.lang.reflect.Type;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Provider;
import javax.inject.Singleton;

import org.xwiki.component.annotation.Component;
import org.xwiki.component.descriptor.ComponentDescriptor;
import org.xwiki.component.manager.ComponentLookupException;
import org.xwiki.component.manager.ComponentManager;
import org.xwiki.query.Query;
import org.xwiki.query.QueryException;
import org.xwiki.query.QueryExecutor;
import org.xwiki.query.QueryExecutorManager;

/**
 * Default implementation of {@link QueryExecutorManager}.
 * 
 * @version $Id: a716918ef3b24146eb1ae1269e8dad40510a09ab $
 */
// Note that we force the Component annotation so that this component is only registered as a
// QueryExecutorManager and not a QueryExecutor too since we don't want this manager to be visible
// to users as a valid QueryExecutor component.
@Component(roles = {QueryExecutorManager.class })
@Singleton
public class DefaultQueryExecutorManager implements QueryExecutorManager
{
    @Inject
    @Named("context")
    private Provider<ComponentManager> componentManagerProvider;

    /**
     * Executor provider for named queries. This provider will give us an executor which is native to the type of
     * storage engine used.
     */
    @Inject
    private Provider<QueryExecutor> namedQueryExecutorProvider;

    @Override
    public <T> List<T> execute(Query query) throws QueryException
    {
        if (query.isNamed()) {
            return this.namedQueryExecutorProvider.get().execute(query);
        } else {
            try {
                return this.componentManagerProvider.get()
                    .<QueryExecutor>getInstance(QueryExecutor.class, query.getLanguage()).execute(query);
            } catch (ComponentLookupException e) {
                throw new QueryException("Fail to lookup query executor", query, e);
            }
        }
    }

    @Override
    public Set<String> getLanguages()
    {
        List<ComponentDescriptor<QueryExecutor>> executors =
            this.componentManagerProvider.get().getComponentDescriptorList((Type) QueryExecutor.class);

        Set<String> executorNames = new HashSet<String>(executors.size());
        for (ComponentDescriptor<QueryExecutor> executor : executors) {
            executorNames.add(executor.getRoleHint());
        }

        return executorNames;
    }
}