core/src/main/java/org/apache/struts2/views/freemarker/StrutsBeanWrapper.java

/*
 * 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.struts2.views.freemarker;

import java.util.Map;
import java.util.Set;

import freemarker.core.CollectionAndSequence;
import freemarker.ext.beans.BeansWrapper;
import freemarker.ext.beans.MapModel;
import freemarker.ext.util.ModelFactory;
import freemarker.template.ObjectWrapper;
import freemarker.template.SimpleSequence;
import freemarker.template.TemplateCollectionModel;
import freemarker.template.TemplateHashModelEx;
import freemarker.template.TemplateModel;
import freemarker.template.Version;

/**
 * <!-- START SNIPPET: javadoc -->
 * <p>
 * The StrutsBeanWrapper extends the default FreeMarker BeansWrapper and provides almost no change in functionality,
 * <b>except</b> for how it handles maps. Normally, FreeMarker has two modes of operation: either support for friendly
 * map built-ins (?keys, ?values, etc) but only support for String keys; OR no special built-in support (ie: ?keys
 * returns the methods on the map instead of the keys) but support for String and non-String keys alike. Struts
 * provides an alternative implementation that gives us the best of both worlds.
 * </p>
 *
 * <p> It is possible that this special behavior may be confusing or can cause problems. Therefore, you can set the
 * <b>struts.freemarker.wrapper.altMap</b> property in struts.properties to false, allowing the normal BeansWrapper
 * logic to take place instead.
 * </p>
 * <!-- END SNIPPET: javadoc -->
 */
public class StrutsBeanWrapper extends BeansWrapper {
    private boolean altMapWrapper;

    public StrutsBeanWrapper(boolean altMapWrapper, Version incompatibleImprovements) {
        super(incompatibleImprovements);
        this.altMapWrapper = altMapWrapper;
    }

    protected ModelFactory getModelFactory(Class clazz) {
        // attempt to get the best of both the SimpleMapModel and the MapModel of FM.
        if (altMapWrapper && Map.class.isAssignableFrom(clazz)) {
            return FriendlyMapModel.FACTORY;
        }

        return super.getModelFactory(clazz);
    }

    /**
     * Attempting to get the best of both worlds of FM's MapModel and SimpleMapModel, by reimplementing the isEmpty(),
     * keySet() and values() methods. ?keys and ?values built-ins are thus available, just as well as plain Map
     * methods.
     */
    private final static class FriendlyMapModel extends MapModel implements TemplateHashModelEx {
        static final ModelFactory FACTORY = new ModelFactory() {
            public TemplateModel create(Object object, ObjectWrapper wrapper) {
                return new FriendlyMapModel((Map) object, (BeansWrapper) wrapper);
            }
        };

        public FriendlyMapModel(Map map, BeansWrapper wrapper) {
            super(map, wrapper);
        }

        public boolean isEmpty() {
            return ((Map) object).isEmpty();
        }

        protected Set keySet() {
            return ((Map) object).keySet();
        }

        public TemplateCollectionModel values() {
            return new CollectionAndSequence(new SimpleSequence(((Map) object).values(), wrapper));
        }
    }
}