001 /* $Id: FinderSetProperties.java 471661 2006-11-06 08:09:25Z skitching $ 002 * 003 * Licensed to the Apache Software Foundation (ASF) under one or more 004 * contributor license agreements. See the NOTICE file distributed with 005 * this work for additional information regarding copyright ownership. 006 * The ASF licenses this file to You under the Apache License, Version 2.0 007 * (the "License"); you may not use this file except in compliance with 008 * the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 019 package org.apache.commons.digester.plugins.strategies; 020 021 import java.util.Properties; 022 023 import org.apache.commons.digester.Digester; 024 import org.apache.commons.digester.plugins.RuleFinder; 025 import org.apache.commons.digester.plugins.RuleLoader; 026 027 /** 028 * A rule-finding algorithm which expects the user to specify whether 029 * "automatic property setting" is desired. If this class discovers that 030 * this is in fact the case for a declaration, then a RuleLoader is returned 031 * which, when invoked, adds a single SetPropertiesRule instance to the 032 * digester. 033 * <p> 034 * This allows ordinary JavaBean classes to be used as plugins, and have 035 * xml attributes be mapped to bean properties of the same name, without 036 * any custom plugin rules being created for them. 037 * <p> 038 * This RuleFinder is typically used as the <i>last</i> RuleFinder, so that 039 * automatic property setting only occurs if there is no other source of 040 * custom rules available. 041 * 042 * @since 1.6 043 */ 044 045 public class FinderSetProperties extends RuleFinder { 046 public static String DFLT_PROPS_ATTR = "setprops"; 047 public static String DFLT_FALSEVAL = "false"; 048 049 private String propsAttr; 050 private String falseval; 051 052 /** See {@link #findLoader}. */ 053 public FinderSetProperties() { 054 this(DFLT_PROPS_ATTR, DFLT_FALSEVAL); 055 } 056 057 /** 058 * Create a rule-finder which will arrange for a SetPropertiesRule to 059 * be defined for each instance of a plugin, so that xml attributes 060 * map to bean properties. 061 * <p> 062 * Param falseval will commonly be the string "false" for config files 063 * written in English. 064 * 065 * @param propsAttr must be non-null. 066 * @param falseval must be non-null. 067 */ 068 public FinderSetProperties(String propsAttr, String falseval) { 069 this.propsAttr = propsAttr; 070 this.falseval = falseval; 071 } 072 073 /** 074 * Returns a RuleLoader <i>unless</i> the properties contain an entry 075 * with the name matching constructor param propsAttr, and the value 076 * matching what is in falseval. 077 * <p> 078 * If no custom source of rules for a plugin is found, then the user 079 * almost always wants xml attributes to map to java bean properties, 080 * so this is the default behaviour unless the user explicitly indicates 081 * that they do <i>not</i> want a SetPropertiesRule to be provided for 082 * the plugged-in class. 083 * <p> 084 * The returned object (when non-null) will add a SetPropertiesRule to 085 * the digester whenever its addRules method is invoked. 086 */ 087 public RuleLoader findLoader(Digester d, Class pluginClass, Properties p) { 088 String state = p.getProperty(propsAttr); 089 if ((state != null) && state.equals(falseval)) { 090 // user has explicitly disabled automatic setting of properties. 091 // this is not expected to be common, but allowed. 092 return null; 093 } 094 095 return new LoaderSetProperties(); 096 } 097 } 098