FetchBindingTemplatesQuery.java

/*
 * Copyright 2001-2008 The Apache Software Foundation.
 * 
 * Licensed 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.apache.juddi.query;

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

import javax.persistence.EntityManager;

import org.apache.commons.configuration.ConfigurationException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.juddi.config.AppConfig;
import org.apache.juddi.config.Property;
import org.apache.juddi.query.util.DynamicQuery;
import org.apache.juddi.query.util.FindQualifiers;
import org.uddi.v3_service.DispositionReportFaultMessage;
import org.uddi.api_v3.ListDescription;

/**
 * The "select" method retrieves all the entities for the input key list and sorts according to the user settings.  Paging is taken into account when retrieving 
 * the results.  The result is a list of the entity objects containing all top level elements (restricted to the given page). 
 * 
 * NOTE:  Results usually need multiple one-to-many collections to be fetched.  Although this could be done in one query with eager fetching, this strategy is not
 * recommended as it will lead to a potentially large Cartesian product.  Therefore, the collections are initialized in separate queries during the mapping 
 * stage.  If the returned results are small (maxRows parameters is set appropriately), a single query is likely faster, but probably not by enough to consider 
 * the optimization under these conditions.
 * 
 * @author <a href="mailto:jfaath@apache.org">Jeff Faath</a>
 */
public class FetchBindingTemplatesQuery extends BindingTemplateQuery {

	private static final Log log = LogFactory.getLog(FetchBindingTemplatesQuery.class);

	protected static final String selectSQL;

	static {
		StringBuilder sql = new StringBuilder(200);
		sql.append("select " + ENTITY_ALIAS + " from " + ENTITY_NAME + " " + ENTITY_ALIAS + " ");
		selectSQL = sql.toString();
	}
	
	public static List<?> select(EntityManager em, FindQualifiers fq, List<?> keysIn, Integer maxRowsUser, Integer listHead, ListDescription listDesc, DynamicQuery.Parameter... restrictions) throws DispositionReportFaultMessage {
		
		// If keysIn is null or empty, then nothing to fetch.
		if ((keysIn == null) || (keysIn.size() == 0))
			return Collections.emptyList();
		int maxRows = DEFAULT_MAXROWS;
		try {
			maxRows = AppConfig.getConfiguration().getInteger(Property.JUDDI_MAX_ROWS, DEFAULT_MAXROWS);
		}
		catch(ConfigurationException ce) {
			log.error("Configuration exception occurred retrieving: " + Property.JUDDI_MAX_ROWS);
		}
		DynamicQuery dynamicQry = new DynamicQuery(selectSQL);
		if (keysIn.size() > maxRows) {
			UUID uuid = UUID.randomUUID();
			storeIntermediateKeySetResults(em, uuid.toString(), keysIn);
			appendTempTable(dynamicQry);
			appendSortTables(dynamicQry);
			appendTempJoin(dynamicQry, uuid.toString());
		}
		else {
			appendSortTables(dynamicQry);
			dynamicQry.appendInListWithAnd(ENTITY_ALIAS + "." + KEY_NAME, keysIn);
		}
		if (restrictions != null && restrictions.length > 0)
			dynamicQry.AND().pad().appendGroupedAnd(restrictions);
		
		appendSortCriteria(dynamicQry, fq);

		log.debug(dynamicQry);
		
		return getPagedResult(em, dynamicQry, maxRowsUser, listHead, listDesc);
	}
	
	private static void appendTempTable(DynamicQuery qry) {
		qry.comma().append(TEMP_ENTITY_NAME + " " +  TEMP_ENTITY_ALIAS );
	}
	
	private static void appendTempJoin(DynamicQuery qry, String uuid) {
		qry.pad().AND().pad().append(TEMP_ENTITY_PK_KEY_NAME).append(DynamicQuery.PREDICATE_EQUALS);
		qry.pad().append(ENTITY_ALIAS + "." + KEY_NAME);
		qry.pad().AND().pad().append(TEMP_ENTITY_PK_TXID_NAME).append(DynamicQuery.PREDICATE_EQUALS);
		qry.append("'" + uuid + "'").pad();
	}
	
	private static void appendSortTables(DynamicQuery qry) {
		// BindingTemplates can only be sorted by date.
		qry.WHERE().pad().append("1=1").pad();
	}
	
	/*
	 *	BindingTemplates can only be sorted by date.
	 */
	private static void appendSortCriteria(DynamicQuery qry, FindQualifiers fq) {
		
		qry.ORDERBY().pad();
		
		if (fq.isSortByDateAsc())
			qry.append(ENTITY_ALIAS + ".modified").pad().append(DynamicQuery.SORT_ASC);
		else
			qry.append(ENTITY_ALIAS + ".modified").pad().append(DynamicQuery.SORT_DESC);
		
		qry.pad();
		
	}

}