001/* 002 * Copyright 2002-2012 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.jdbc.core; 018 019import java.sql.ResultSet; 020import java.sql.SQLException; 021import java.util.ArrayList; 022import java.util.List; 023 024import org.springframework.util.Assert; 025 026/** 027 * Adapter implementation of the ResultSetExtractor interface that delegates 028 * to a RowMapper which is supposed to create an object for each row. 029 * Each object is added to the results List of this ResultSetExtractor. 030 * 031 * <p>Useful for the typical case of one object per row in the database table. 032 * The number of entries in the results list will match the number of rows. 033 * 034 * <p>Note that a RowMapper object is typically stateless and thus reusable; 035 * just the RowMapperResultSetExtractor adapter is stateful. 036 * 037 * <p>A usage example with JdbcTemplate: 038 * 039 * <pre class="code">JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource); // reusable object 040 * RowMapper rowMapper = new UserRowMapper(); // reusable object 041 * 042 * List allUsers = (List) jdbcTemplate.query( 043 * "select * from user", 044 * new RowMapperResultSetExtractor(rowMapper, 10)); 045 * 046 * User user = (User) jdbcTemplate.queryForObject( 047 * "select * from user where id=?", new Object[] {id}, 048 * new RowMapperResultSetExtractor(rowMapper, 1));</pre> 049 * 050 * <p>Alternatively, consider subclassing MappingSqlQuery from the {@code jdbc.object} 051 * package: Instead of working with separate JdbcTemplate and RowMapper objects, 052 * you can have executable query objects (containing row-mapping logic) there. 053 * 054 * @author Juergen Hoeller 055 * @since 1.0.2 056 * @see RowMapper 057 * @see JdbcTemplate 058 * @see org.springframework.jdbc.object.MappingSqlQuery 059 */ 060public class RowMapperResultSetExtractor<T> implements ResultSetExtractor<List<T>> { 061 062 private final RowMapper<T> rowMapper; 063 064 private final int rowsExpected; 065 066 067 /** 068 * Create a new RowMapperResultSetExtractor. 069 * @param rowMapper the RowMapper which creates an object for each row 070 */ 071 public RowMapperResultSetExtractor(RowMapper<T> rowMapper) { 072 this(rowMapper, 0); 073 } 074 075 /** 076 * Create a new RowMapperResultSetExtractor. 077 * @param rowMapper the RowMapper which creates an object for each row 078 * @param rowsExpected the number of expected rows 079 * (just used for optimized collection handling) 080 */ 081 public RowMapperResultSetExtractor(RowMapper<T> rowMapper, int rowsExpected) { 082 Assert.notNull(rowMapper, "RowMapper is required"); 083 this.rowMapper = rowMapper; 084 this.rowsExpected = rowsExpected; 085 } 086 087 088 @Override 089 public List<T> extractData(ResultSet rs) throws SQLException { 090 List<T> results = (this.rowsExpected > 0 ? new ArrayList<T>(this.rowsExpected) : new ArrayList<T>()); 091 int rowNum = 0; 092 while (rs.next()) { 093 results.add(this.rowMapper.mapRow(rs, rowNum++)); 094 } 095 return results; 096 } 097 098}