1 package org.apache.commons.digester3.plugins.strategies;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import java.util.Properties;
23
24 import org.apache.commons.digester3.Digester;
25 import org.apache.commons.digester3.plugins.PluginException;
26 import org.apache.commons.digester3.plugins.RuleFinder;
27 import org.apache.commons.digester3.plugins.RuleLoader;
28
29 /**
30 * A rule-finding algorithm which expects the user to specify whether "automatic property setting" is desired. If this
31 * class discovers that this is in fact the case for a declaration, then a RuleLoader is returned which, when invoked,
32 * adds a single SetPropertiesRule instance to the digester.
33 * <p>
34 * This allows ordinary JavaBean classes to be used as plugins, and have xml attributes be mapped to bean properties of
35 * the same name, without any custom plugin rules being created for them.
36 * <p>
37 * This RuleFinder is typically used as the <i>last</i> RuleFinder, so that automatic property setting only occurs if
38 * there is no other source of custom rules available.
39 *
40 * @since 1.6
41 */
42 public class FinderSetProperties
43 extends RuleFinder
44 {
45
46 private static final String DFLT_PROPS_ATTR = "setprops";
47
48 private static final String DFLT_FALSEVAL = "false";
49
50 private final String propsAttr;
51
52 private final String falseval;
53
54 /** See {@link #findLoader}. */
55 public FinderSetProperties()
56 {
57 this( DFLT_PROPS_ATTR, DFLT_FALSEVAL );
58 }
59
60 /**
61 * Create a rule-finder which will arrange for a SetPropertiesRule to be defined for each instance of a plugin, so
62 * that xml attributes map to bean properties.
63 * <p>
64 * Param falseval will commonly be the string "false" for config files written in English.
65 *
66 * @param propsAttr must be non-null.
67 * @param falseval must be non-null.
68 */
69 public FinderSetProperties( String propsAttr, String falseval )
70 {
71 this.propsAttr = propsAttr;
72 this.falseval = falseval;
73 }
74
75 /**
76 * Returns a RuleLoader <i>unless</i> the properties contain an entry with the name matching constructor param
77 * propsAttr, and the value matching what is in falseval.
78 * <p>
79 * If no custom source of rules for a plugin is found, then the user almost always wants xml attributes to map to
80 * java bean properties, so this is the default behaviour unless the user explicitly indicates that they do
81 * <i>not</i> want a SetPropertiesRule to be provided for the plugged-in class.
82 * <p>
83 * The returned object (when non-null) will add a SetPropertiesRule to the digester whenever its addRules method is
84 * invoked.
85 *
86 * @param d The digester instance where locating plugin classes
87 * @param pluginClass The plugin Java class
88 * @param p The properties object that holds any xml attributes the user may have specified on the plugin
89 * declaration in order to indicate how to locate the plugin rules.
90 * @return a source of digester rules for the specified plugin class.
91 * @throws PluginException if the algorithm finds a source of rules, but there is something invalid
92 * about that source.
93 */
94 @Override
95 public RuleLoader findLoader( Digester d, Class<?> pluginClass, Properties p )
96 throws PluginException
97 {
98 String state = p.getProperty( propsAttr );
99 if ( ( state != null ) && state.equals( falseval ) )
100 {
101 // user has explicitly disabled automatic setting of properties.
102 // this is not expected to be common, but allowed.
103 return null;
104 }
105
106 return new LoaderSetProperties();
107 }
108
109 }