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Google App Engine compliant variation of FreeMarker. FreeMarker is a "template engine"; a generic tool to generate text output based on templates.
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/*
 * 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 freemarker.ext.beans;

import java.beans.IndexedPropertyDescriptor;
import java.beans.PropertyDescriptor;

import freemarker.ext.beans.BeansWrapper.MethodAppearanceDecision;
import freemarker.ext.beans.BeansWrapper.MethodAppearanceDecisionInput;

/**
 * Used for customizing how the methods are visible from templates, via
 * {@link BeansWrapper#setMethodAppearanceFineTuner(MethodAppearanceFineTuner)}.
 * The object that implements this should also implement {@link SingletonCustomizer} whenever possible.
 * 
 * @since 2.3.21
 */
public interface MethodAppearanceFineTuner {

    /**
     * Implement this to tweak certain aspects of how methods appear in the
     * data-model. {@link BeansWrapper} will pass in all Java methods here that
     * it intends to expose in the data-model as methods (so you can do
     * obj.foo() in the template).
     * With this method you can do the following tweaks:
     * 
     *   Hide a method that would be otherwise shown by calling
     *     {@link MethodAppearanceDecision#setExposeMethodAs(String)}
     *     with null parameter. Note that you can't un-hide methods
     *     that are not public or are considered to by unsafe
     *     (like {@link Object#wait()}) because
     *     {@link #process} is not called for those.
     *   Show the method with a different name in the data-model than its
     *     real name by calling
     *     {@link MethodAppearanceDecision#setExposeMethodAs(String)}
     *     with non-null parameter.
     *   
Create a fake JavaBean property for this method by calling
     *     {@link MethodAppearanceDecision#setExposeAsProperty(PropertyDescriptor)}.
     *     For example, if you have int size() in a class, but you
     *     want it to be accessed from the templates as obj.size,
     *     rather than as obj.size(), you can do that with this.
     *     The default is {@code null}, which means that no fake property is
     *     created for the method. You need not and shouldn't set this
     *     to non-null for the getter methods of real JavaBean
     *     properties, as those are automatically shown as properties anyway.
     *     The property name in the {@link PropertyDescriptor} can be anything,
     *     but the method (or methods) in it must belong to the class that
     *     is given as the clazz parameter or it must be inherited from
     *     that class, or else whatever errors can occur later.
     *     {@link IndexedPropertyDescriptor}-s are supported.
     *     If a real JavaBean property of the same name exists, it won't be
     *     replaced by the fake one. Also if a fake property of the same name
     *     was assigned earlier, it won't be replaced.
     *   
Prevent the method to hide a JavaBean property (fake or real) of
     *     the same name by calling
     *     {@link MethodAppearanceDecision#setMethodShadowsProperty(boolean)}
     *     with false. The default is true, so if you have
     *     both a property and a method called "foo", then in the template
     *     myObject.foo will return the method itself instead
     *     of the property value, which is often undesirable.
     * 
     * 
     * Note that you can expose a Java method both as a method and as a
     * JavaBean property on the same time, however you have to chose different
     * names for them to prevent shadowing. 
     * 
     * @param in Describes the method about which the decision will have to be made.
     *  
     * @param out Stores how the method will be exposed in the
     *   data-model after {@link #process} returns.
     *   This is initialized so that it reflects the default
     *   behavior of {@link BeansWrapper}, so you don't have to do anything with this
     *   when you don't want to change the default behavior.
     */
    void process(MethodAppearanceDecisionInput in, MethodAppearanceDecision out);    
    
}