Commons Digester example source code file (FinderSetProperties.java)

This example Commons Digester source code file (FinderSetProperties.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Digester tags/keywords

class, dflt_falseval, dflt_falseval, dflt_props_attr, findersetproperties, findersetproperties, loadersetproperties, loadersetproperties, override, properties, rulefinder, ruleloader, string, string, util

The Commons Digester FinderSetProperties.java source code

/* $Id: FinderSetProperties.java 992060 2010-09-02 19:09:47Z simonetripodi $
 *
 * 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.digester.plugins.strategies;

import java.util.Properties;

import org.apache.commons.digester.Digester;
import org.apache.commons.digester.plugins.RuleFinder;
import org.apache.commons.digester.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.
 * <p>
 * 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.
 * <p>
 * This RuleFinder is typically used as the <i>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 {
    public static String DFLT_PROPS_ATTR = "setprops";
    public static String DFLT_FALSEVAL = "false";

    private String propsAttr;
    private 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.
     * <p>
     * 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 <i>unless the properties contain an entry
     * with the name matching constructor param propsAttr, and the value 
     * matching what is in falseval.
     * <p>
     * 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 <i>not want a SetPropertiesRule to be provided for
     * the plugged-in class.
     * <p>
     * The returned object (when non-null) will add a SetPropertiesRule to
     * the digester whenever its addRules method is invoked.
     */
    @Override
    public RuleLoader findLoader(Digester d, Class<?> pluginClass, Properties p) {
        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();
    }
}