org.apache.commons.digester3.plugins.strategies.FinderSetProperties Maven / Gradle / Ivy
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package org.apache.commons.digester3.plugins.strategies;
/*
* 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.
*/
import java.util.Properties;
import org.apache.commons.digester3.Digester;
import org.apache.commons.digester3.plugins.PluginException;
import org.apache.commons.digester3.plugins.RuleFinder;
import org.apache.commons.digester3.plugins.RuleLoader;
/**
* A rule-finding algorithm which expects the user to specify whether "automatic property setting" is desired. If this
* class discovers that this is in fact the case for a declaration, then a RuleLoader is returned which, when invoked,
* adds a single SetPropertiesRule instance to the digester.
*
* This allows ordinary JavaBean classes to be used as plugins, and have xml attributes be mapped to bean properties of
* the same name, without any custom plugin rules being created for them.
*
* This RuleFinder is typically used as the last RuleFinder, so that automatic property setting only occurs if
* there is no other source of custom rules available.
*
* @since 1.6
*/
public class FinderSetProperties
extends RuleFinder
{
private static final String DFLT_PROPS_ATTR = "setprops";
private static final String DFLT_FALSEVAL = "false";
private final String propsAttr;
private final String falseval;
/** See {@link #findLoader}. */
public FinderSetProperties()
{
this( DFLT_PROPS_ATTR, DFLT_FALSEVAL );
}
/**
* Create a rule-finder which will arrange for a SetPropertiesRule to be defined for each instance of a plugin, so
* that xml attributes map to bean properties.
*
* Param falseval will commonly be the string "false" for config files written in English.
*
* @param propsAttr must be non-null.
* @param falseval must be non-null.
*/
public FinderSetProperties( String propsAttr, String falseval )
{
this.propsAttr = propsAttr;
this.falseval = falseval;
}
/**
* Returns a RuleLoader unless the properties contain an entry with the name matching constructor param
* propsAttr, and the value matching what is in falseval.
*
* If no custom source of rules for a plugin is found, then the user almost always wants xml attributes to map to
* java bean properties, so this is the default behaviour unless the user explicitly indicates that they do
* not want a SetPropertiesRule to be provided for the plugged-in class.
*
* The returned object (when non-null) will add a SetPropertiesRule to the digester whenever its addRules method is
* invoked.
*
* @param d The digester instance where locating plugin classes
* @param pluginClass The plugin Java class
* @param p The properties object that holds any xml attributes the user may have specified on the plugin
* declaration in order to indicate how to locate the plugin rules.
* @return a source of digester rules for the specified plugin class.
* @throws PluginException if the algorithm finds a source of rules, but there is something invalid
* about that source.
*/
@Override
public RuleLoader findLoader( Digester d, Class pluginClass, Properties p )
throws PluginException
{
String state = p.getProperty( propsAttr );
if ( ( state != null ) && state.equals( falseval ) )
{
// user has explicitly disabled automatic setting of properties.
// this is not expected to be common, but allowed.
return null;
}
return new LoaderSetProperties();
}
}