    001    /* $Id: FinderSetProperties.java 729125 2008-12-23 21:21:07Z rahul $
    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