001 // Copyright 2004, 2005 The Apache Software Foundation 002 // 003 // Licensed under the Apache License, Version 2.0 (the "License"); 004 // you may not use this file except in compliance with the License. 005 // You may obtain a copy of the License at 006 // 007 // http://www.apache.org/licenses/LICENSE-2.0 008 // 009 // Unless required by applicable law or agreed to in writing, software 010 // distributed under the License is distributed on an "AS IS" BASIS, 011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012 // See the License for the specific language governing permissions and 013 // limitations under the License. 014 015 package org.apache.tapestry.contrib.table.model.simple; 016 017 import java.util.Comparator; 018 019 /** 020 * In order to provide more generic behaviour, ITableColumn 021 * has no "column value" concept. The comparator it returns 022 * compares two table rows, rather than values specific to the column. 023 * <p> 024 * SimpleTableColumn introduces the concept of "column value" and 025 * allows one to extract that "column value" from the row using 026 * the getColumnValue() method. In practice comparisons are also typically 027 * done between these values rather than the full row objects. 028 * <p> 029 * This comparator extracts the column values from the rows passed 030 * and uses the provided comparator to compare the values. 031 * It therefore allows a comparator designed for comparing column values to be 032 * quickly wrapped and used as a comparator comparing rows, which is what 033 * ITableColumn is expected to return. 034 * <p> 035 * Example: 036 * <p> 037 * objColumn.setComparator(new ColumnComparator(objColumn, objBeanComparator)); 038 * 039 * @author mindbridge 040 * 041 */ 042 public class ColumnComparator implements Comparator 043 { 044 private SimpleTableColumn m_objColumn; 045 private Comparator m_objComparator; 046 047 public ColumnComparator(SimpleTableColumn objColumn, Comparator objComparator) 048 { 049 m_objColumn = objColumn; 050 m_objComparator = objComparator; 051 } 052 053 /** 054 * @see java.util.Comparator#compare(Object, Object) 055 */ 056 public int compare(Object objRow1, Object objRow2) 057 { 058 Object objValue1 = m_objColumn.getColumnValue(objRow1); 059 Object objValue2 = m_objColumn.getColumnValue(objRow2); 060 061 return m_objComparator.compare(objValue1, objValue2); 062 } 063 064 }