001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.dbutils.handlers;
018    
019    import java.sql.ResultSet;
020    import java.sql.SQLException;
021    import java.util.HashMap;
022    import java.util.Map;
023    
024    import org.apache.commons.dbutils.ResultSetHandler;
025    
026    /**
027     * <p>
028     * <code>ResultSetHandler</code> implementation that returns a Map.
029     * <code>ResultSet</code> rows are converted into objects (Vs) which are then stored
030     * in a Map under the given keys (Ks).
031     * </p>
032     * 
033     * @see org.apache.commons.dbutils.ResultSetHandler
034     * @since DbUtils 1.3
035     */
036    public abstract class AbstractKeyedHandler<K,V> implements ResultSetHandler<Map<K,V>> {
037    
038    
039        /**
040         * Convert each row's columns into a Map and store then 
041         * in a <code>Map</code> under <code>ResultSet.getObject(key)</code> key.
042         * @param rs <code>ResultSet</code> to process.
043         * @return A <code>Map</code>, never <code>null</code>. 
044         * @throws SQLException if a database access error occurs
045         * @see org.apache.commons.dbutils.ResultSetHandler#handle(java.sql.ResultSet)
046         */
047        public Map<K,V> handle(ResultSet rs) throws SQLException {
048            Map<K,V> result = createMap();
049            while (rs.next()) {
050                result.put(createKey(rs), createRow(rs));
051            }
052            return result;
053        }
054    
055        /**
056         * This factory method is called by <code>handle()</code> to create the Map
057         * to store records in.  This implementation returns a <code>HashMap</code>
058         * instance.
059         *
060         * @return Map to store records in
061         */
062        protected Map<K,V> createMap() {
063            return new HashMap<K,V>();
064        }
065    
066        /**
067         * This factory method is called by <code>handle()</code> to retrieve the
068         * key value from the current <code>ResultSet</code> row.
069         * @param rs ResultSet to create a key from
070         * @return K from the configured key column name/index
071         * @throws SQLException if a database access error occurs
072         */
073        protected abstract K createKey(ResultSet rs) throws SQLException;
074    
075        /**
076         * This factory method is called by <code>handle()</code> to store the
077         * current <code>ResultSet</code> row in some object.
078         * @param rs ResultSet to create a row from
079         * @return V object created from the current row
080         * @throws SQLException if a database access error occurs
081         */
082        protected abstract V createRow(ResultSet rs) throws SQLException;
083    
084    }