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; 021 022 import org.apache.commons.dbutils.ResultSetHandler; 023 024 /** 025 * <code>ResultSetHandler</code> implementation that converts one 026 * <code>ResultSet</code> column into an Object. This class is thread safe. 027 * 028 * @see org.apache.commons.dbutils.ResultSetHandler 029 */ 030 public class ScalarHandler implements ResultSetHandler { 031 032 /** 033 * The column number to retrieve. 034 */ 035 private final int columnIndex; 036 037 /** 038 * The column name to retrieve. Either columnName or columnIndex 039 * will be used but never both. 040 */ 041 private final String columnName; 042 043 /** 044 * Creates a new instance of ScalarHandler. The first column will 045 * be returned from <code>handle()</code>. 046 */ 047 public ScalarHandler() { 048 this(1, null); 049 } 050 051 /** 052 * Creates a new instance of ScalarHandler. 053 * 054 * @param columnIndex The index of the column to retrieve from the 055 * <code>ResultSet</code>. 056 */ 057 public ScalarHandler(int columnIndex) { 058 this(columnIndex, null); 059 } 060 061 /** 062 * Creates a new instance of ScalarHandler. 063 * 064 * @param columnName The name of the column to retrieve from the 065 * <code>ResultSet</code>. 066 */ 067 public ScalarHandler(String columnName) { 068 this(1, columnName); 069 } 070 071 // Helper constructor 072 private ScalarHandler(int columnIndex, String columnName){ 073 this.columnIndex = columnIndex; 074 this.columnName = columnName; 075 } 076 077 /** 078 * Returns one <code>ResultSet</code> column as an object via the 079 * <code>ResultSet.getObject()</code> method that performs type 080 * conversions. 081 * 082 * @return The column or <code>null</code> if there are no rows in 083 * the <code>ResultSet</code>. 084 * 085 * @throws SQLException if a database access error occurs 086 * 087 * @see org.apache.commons.dbutils.ResultSetHandler#handle(java.sql.ResultSet) 088 */ 089 public Object handle(ResultSet rs) throws SQLException { 090 091 if (rs.next()) { 092 if (this.columnName == null) { 093 return rs.getObject(this.columnIndex); 094 } else { 095 return rs.getObject(this.columnName); 096 } 097 098 } else { 099 return null; 100 } 101 } 102 }