ColumnListHandler

/* * 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;/** * <code>ResultSetHandler</code> implementation that converts one * <code>ResultSet</code> column into a <code>List</code> of * <code>Object</code>s. This class is thread safe. * * @param <T> The type of the column. * @see org.apache.commons.dbutils.ResultSetHandler * @since DbUtils 1.1 */public class ColumnListHandler<T> extends AbstractListHandler<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 ColumnListHandler.  The first column of each     * row will be returned from <code>handle()</code>.     */    public ColumnListHandler() {        this(1, null);    }    /**     * Creates a new instance of ColumnListHandler.     *     * @param columnIndex The index of the column to retrieve from the     * <code>ResultSet</code>.     */    public ColumnListHandler(int columnIndex) {        this(columnIndex, null);    }    /**     * Creates a new instance of ColumnListHandler.     *     * @param columnName The name of the column to retrieve from the     * <code>ResultSet</code>.     */    public ColumnListHandler(String columnName) {        this(1, columnName);    }    /** Private Helper     * @param columnIndex The index of the column to retrieve from the     * <code>ResultSet</code>.     * @param columnName The name of the column to retrieve from the     * <code>ResultSet</code>.     */    private ColumnListHandler(int columnIndex, String columnName) {        super();        this.columnIndex = columnIndex;        this.columnName = columnName;    }    /**     * Returns one <code>ResultSet</code> column value as <code>Object</code>.     * @param rs <code>ResultSet</code> to process.     * @return <code>Object</code>, never <code>null</code>.     *     * @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.handlers.AbstractListHandler#handle(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    protected T handleRow(ResultSet rs) throws SQLException {        if (this.columnName == null) {            return (T) rs.getObject(this.columnIndex);        } else {            return (T) rs.getObject(this.columnName);        }   }}