1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.dbutils.handlers;
18
19 import java.sql.ResultSet;
20 import java.sql.SQLException;
21 import java.util.HashMap;
22 import java.util.Map;
23
24 import org.apache.commons.dbutils.ResultSetHandler;
25
26 /**
27 * <p>
28 * {@code ResultSetHandler} implementation that returns a Map.
29 * {@code ResultSet} rows are converted into objects (Vs) which are then stored
30 * in a Map under the given keys (Ks).
31 * </p>
32 *
33 * @param <K> the type of keys maintained by the returned map
34 * @param <V> the type of mapped values
35 * @see org.apache.commons.dbutils.ResultSetHandler
36 * @since 1.3
37 */
38 public abstract class AbstractKeyedHandler<K, V> implements ResultSetHandler<Map<K, V>> {
39
40 /**
41 * This factory method is called by {@code handle()} to retrieve the
42 * key value from the current {@code ResultSet} row.
43 * @param resultSet ResultSet to create a key from
44 * @return K from the configured key column name/index
45 * @throws SQLException if a database access error occurs
46 */
47 protected abstract K createKey(ResultSet resultSet) throws SQLException;
48
49 /**
50 * This factory method is called by {@code handle()} to create the Map
51 * to store records in. This implementation returns a {@code HashMap}
52 * instance.
53 *
54 * @return Map to store records in
55 */
56 protected Map<K, V> createMap() {
57 return new HashMap<>();
58 }
59
60 /**
61 * This factory method is called by {@code handle()} to store the
62 * current {@code ResultSet} row in some object.
63 * @param resultSet ResultSet to create a row from
64 * @return V object created from the current row
65 * @throws SQLException if a database access error occurs
66 */
67 protected abstract V createRow(ResultSet resultSet) throws SQLException;
68
69 /**
70 * Convert each row's columns into a Map and store then
71 * in a {@code Map} under {@code ResultSet.getObject(key)} key.
72 * @param resultSet {@code ResultSet} to process.
73 * @return A {@code Map}, never {@code null}.
74 * @throws SQLException if a database access error occurs
75 * @see org.apache.commons.dbutils.ResultSetHandler#handle(java.sql.ResultSet)
76 */
77 @Override
78 public Map<K, V> handle(final ResultSet resultSet) throws SQLException {
79 final Map<K, V> result = createMap();
80 while (resultSet.next()) {
81 result.put(createKey(resultSet), createRow(resultSet));
82 }
83 return result;
84 }
85
86 }