    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 */
    017package org.apache.commons.dbutils.handlers;
    018
    019import java.sql.ResultSet;
    020import java.sql.SQLException;
    021import java.util.HashMap;
    022import java.util.Map;
    023
    024import org.apache.commons.dbutils.ResultSetHandler;
    025
    026/**
    027 * <p>
    028 * {@code ResultSetHandler} implementation that returns a Map.
    029 * {@code ResultSet} rows are converted into objects (Vs) which are then stored
    030 * in a Map under the given keys (Ks).
    031 * </p>
    032 *
    033 * @param <K> the type of keys maintained by the returned map
    034 * @param <V> the type of mapped values
    035 * @see org.apache.commons.dbutils.ResultSetHandler
    036 * @since 1.3
    037 */
    038public abstract class AbstractKeyedHandler<K, V> implements ResultSetHandler<Map<K, V>> {
    039
    040    /**
    041     * This factory method is called by {@code handle()} to retrieve the
    042     * key value from the current {@code ResultSet} row.
    043     * @param resultSet ResultSet to create a key from
    044     * @return K from the configured key column name/index
    045     * @throws SQLException if a database access error occurs
    046     */
    047    protected abstract K createKey(ResultSet resultSet) throws SQLException;
    048
    049    /**
    050     * This factory method is called by {@code handle()} to create the Map
    051     * to store records in.  This implementation returns a {@code HashMap}
    052     * instance.
    053     *
    054     * @return Map to store records in
    055     */
    056    protected Map<K, V> createMap() {
    057        return new HashMap<>();
    058    }
    059
    060    /**
    061     * This factory method is called by {@code handle()} to store the
    062     * current {@code ResultSet} row in some object.
    063     * @param resultSet ResultSet to create a row from
    064     * @return V object created from the current row
    065     * @throws SQLException if a database access error occurs
    066     */
    067    protected abstract V createRow(ResultSet resultSet) throws SQLException;
    068
    069    /**
    070     * Convert each row's columns into a Map and store then
    071     * in a {@code Map} under {@code ResultSet.getObject(key)} key.
    072     * @param resultSet {@code ResultSet} to process.
    073     * @return A {@code Map}, never {@code null}.
    074     * @throws SQLException if a database access error occurs
    075     * @see org.apache.commons.dbutils.ResultSetHandler#handle(java.sql.ResultSet)
    076     */
    077    @Override
    078    public Map<K, V> handle(final ResultSet resultSet) throws SQLException {
    079        final Map<K, V> result = createMap();
    080        while (resultSet.next()) {
    081            result.put(createKey(resultSet), createRow(resultSet));
    082        }
    083        return result;
    084    }
    085
    086}