| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.dbutils.handlers; |
| |
| import java.sql.ResultSet; |
| import java.sql.SQLException; |
| |
| import org.apache.commons.dbutils.ResultSetHandler; |
| |
| /** |
| * {@code ResultSetHandler} implementation that converts one |
| * {@code ResultSet} column into an Object. This class is thread safe. |
| * |
| * @param <T> The type of the scalar |
| * @see org.apache.commons.dbutils.ResultSetHandler |
| */ |
| public class ScalarHandler<T> implements ResultSetHandler<T> { |
| |
| /** |
| * The column number to retrieve. |
| */ |
| private final int columnIndex; |
| |
| /** |
| * The column name to retrieve. Either columnName or columnIndex |
| * will be used but never both. |
| */ |
| private final String columnName; |
| |
| /** |
| * Creates a new instance of ScalarHandler. The first column will |
| * be returned from {@code handle()}. |
| */ |
| public ScalarHandler() { |
| this(1, null); |
| } |
| |
| /** |
| * Creates a new instance of ScalarHandler. |
| * |
| * @param columnIndex The index of the column to retrieve from the |
| * {@code ResultSet}. |
| */ |
| public ScalarHandler(final int columnIndex) { |
| this(columnIndex, null); |
| } |
| |
| /** |
| * Creates a new instance of ScalarHandler. |
| * |
| * @param columnName The name of the column to retrieve from the |
| * {@code ResultSet}. |
| */ |
| public ScalarHandler(final String columnName) { |
| this(1, columnName); |
| } |
| |
| /** Helper constructor |
| * @param columnIndex The index of the column to retrieve from the |
| * {@code ResultSet}. |
| * @param columnName The name of the column to retrieve from the |
| * {@code ResultSet}. |
| */ |
| private ScalarHandler(final int columnIndex, final String columnName) { |
| this.columnIndex = columnIndex; |
| this.columnName = columnName; |
| } |
| |
| /** |
| * Returns one {@code ResultSet} column as an object via the |
| * {@code ResultSet.getObject()} method that performs type |
| * conversions. |
| * @param rs {@code ResultSet} to process. |
| * @return The column or {@code null} if there are no rows in |
| * the {@code ResultSet}. |
| * |
| * @throws SQLException if a database access error occurs |
| * @throws ClassCastException if the class datatype does not match the column type |
| * |
| * @see org.apache.commons.dbutils.ResultSetHandler#handle(java.sql.ResultSet) |
| */ |
| // We assume that the user has picked the correct type to match the column |
| // so getObject will return the appropriate type and the cast will succeed. |
| @SuppressWarnings("unchecked") |
| @Override |
| public T handle(final ResultSet rs) throws SQLException { |
| |
| if (rs.next()) { |
| if (this.columnName == null) { |
| return (T) rs.getObject(this.columnIndex); |
| } |
| return (T) rs.getObject(this.columnName); |
| } |
| return null; |
| } |
| } |