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/*
 * Copyright 2010 Google Inc.
 * 
 * Licensed 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 com.google.web.bindery.autobean.shared;

import java.util.Collection;
import java.util.Map;

/**
 * Allows traversal of an AutoBean object graph.
 */
public class AutoBeanVisitor {
  /**
   * A PropertyContext that describes the parameterization of the Collection
   * being visited.
   */
  public interface CollectionPropertyContext extends PropertyContext {
    /**
     * Returns the collection's element type.
     * 
     * @return a Class object representing the element type
     */
    Class getElementType();
  }

  /**
   * Reserved for future expansion to avoid API breaks.
   */
  public interface Context {
  }

  /**
   * A PropertyContext that describes the parameterization of the Map being
   * visited.
   */
  public interface MapPropertyContext extends PropertyContext {
    /**
     * Returns the map's key type.
     * 
     * @return a Class object representing the key type
     */
    Class getKeyType();

    /**
     * Returns the map's value type.
     * 
     * @return a Class object representing the value type
     */
    Class getValueType();
  }

  /**
   * The ParameterizationVisitor provides access to more complete type
   * information than a simple class literal can provide.
   * 

* The order of traversal reflects the declared parameterization of the * property. For example, a {@code Map>} would be traversed * via the following sequence: * *

   * visitType(Map.class);
   *   visitParameter();
   *     visitType(String.class);
   *     endVisitType(String.class);
   *   endVisitParameter();
   *   visitParameter();
   *     visitType(List.class);
   *       visitParameter();
   *         visitType(Foo.class);
   *         endVisitType(Foo.class);
   *       endParameter();
   *     endVisitType(List.class);
   *   endVisitParameter();
   * endVisitType(Map.class);
   * 
*/ public static class ParameterizationVisitor { /** * Called when finished with a type parameter. */ public void endVisitParameter() { } /** * Called when finished with a type. * * @param type a Class object */ public void endVisitType(Class type) { } /** * Called when visiting a type parameter. * * @return {@code true} if the type parameter should be visited */ public boolean visitParameter() { return true; } /** * Called when visiting a possibly parameterized type. * * @param type a Class object * @return {@code true} if the type should be visited */ public boolean visitType(Class type) { return true; } } /** * Allows properties to be reset. */ public interface PropertyContext { /** * Allows deeper inspection of the declared parameterization of the * property. */ void accept(ParameterizationVisitor visitor); /** * Indicates if the {@link #set} method will succeed. * * @return {@code true} if the property can be set */ boolean canSet(); /** * Returns the expected type of the property. * * @return a Class object representing the property type */ Class getType(); /** * Sets a property value. * * @param value the new value */ void set(Object value); } /** * Called after visiting an {@link AutoBean}. * * @param bean an {@link AutoBean} * @param ctx a Context */ public void endVisit(AutoBean bean, Context ctx) { } /** * Called after visiting a reference property. * * @param propertyName the property name, as a String * @param value the property value * @param ctx a PropertyContext */ public void endVisitCollectionProperty(String propertyName, AutoBean> value, CollectionPropertyContext ctx) { endVisitReferenceProperty(propertyName, value, ctx); } /** * Called after visiting a reference property. * * @param propertyName the property name, as a String * @param value the property value * @param ctx a PropertyContext */ public void endVisitMapProperty(String propertyName, AutoBean> value, MapPropertyContext ctx) { endVisitReferenceProperty(propertyName, value, ctx); } /** * Called after visiting a reference property. * * @param propertyName the property name, as a String * @param value the property value * @param ctx a PropertyContext */ public void endVisitReferenceProperty(String propertyName, AutoBean value, PropertyContext ctx) { } /** * Called after visiting a value property. * * @param propertyName the property name, as a String * @param value the property value * @param ctx a PropertyContext */ public void endVisitValueProperty(String propertyName, Object value, PropertyContext ctx) { } /** * Called when visiting an {@link AutoBean}. * * @param bean an {@link AutoBean} * @param ctx a Context */ public boolean visit(AutoBean bean, Context ctx) { return true; } /** * Called every time, but {@link #visit(AutoBean, Context)} will be called for * the value only the first time it is encountered. * * @param propertyName the property name, as a String * @param value the property value * @param ctx a PropertyContext */ public boolean visitCollectionProperty(String propertyName, AutoBean> value, CollectionPropertyContext ctx) { return visitReferenceProperty(propertyName, value, ctx); } /** * Called every time, but {@link #visit(AutoBean, Context)} will be called for * the value only the first time it is encountered. * * @param propertyName the property name, as a String * @param value the property value * @param ctx a PropertyContext */ public boolean visitMapProperty(String propertyName, AutoBean> value, MapPropertyContext ctx) { return visitReferenceProperty(propertyName, value, ctx); } /** * Called every time, but {@link #visit(AutoBean, Context)} will be called for * the value only the first time it is encountered. * * @param propertyName the property name, as a String * @param value the property value * @param ctx a PropertyContext */ public boolean visitReferenceProperty(String propertyName, AutoBean value, PropertyContext ctx) { return true; } /** * TODO: document. * * @param propertyName the property name, as a String * @param value the property value * @param ctx a PropertyContext */ public boolean visitValueProperty(String propertyName, Object value, PropertyContext ctx) { return true; } }




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