content: /*
   * Strategy.java July 2006
   *
   * Copyright (C) 2006, Niall Gallagher <niallg@users.sf.net>
   *
   * 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.aliyun.odps.simpleframework.xml.strategy;
  
  import com.aliyun.odps.simpleframework.xml.core.Persister;
  import com.aliyun.odps.simpleframework.xml.stream.NodeMap;
  import com.aliyun.odps.simpleframework.xml.stream.OutputNode;
  import java.util.Map;
  
  import com.aliyun.odps.simpleframework.xml.stream.InputNode;
  
  /**
   * The <code>Strategy</code> interface represents a strategy that can be 
   * used to resolve and load the <code>Class</code> objects that compose 
   * a serializable object. A strategy implementation will make use of the
   * provided attribute node map to extract details that can be used to
   * determine what type of object must be used. 
   * <pre>
   * 
   *    &lt;xml version="1.0"&gt;
   *    &lt;example class="some.example.Demo"&gt;
   *       &lt;integer&gt;2&lt;/integer&gt;
   *    &lt;/example&gt;
   *    
   * </pre> 
   * The above example shows how the default strategy augments elements
   * with "class" attributes that describe the type that should be used
   * to instantiate a field when an object is deserialized. So looking at
   * the above example the root element would be a "some.example.Demo".
   * <p>
   * Custom <code>Strategy</code> implementations give the persister a
   * chance to intercept the class loading and type resolution for XML
   * documents. It also opens up the possibility for class versioning.
   * To establish contextual information a <code>Map</code> object can be
   * used. The map object is a transient object that is created and used
   * for the duration of a single operation of the persister.
   * 
   * @author Niall Gallagher
   *
   * @see Persister
   */
  public interface Strategy {
  
     /**
      * This is used to resolve and load a class for the given element.
      * The class should be of the same type or a subclass of the class
      * specified. It can be resolved using the details within the
      * provided XML node map, if the details used do not represent any
      * serializable values they should be removed so as not to disrupt
      * the deserialization process. For example the default strategy
      * removes all "class" attributes from the given node map.
      * 
      * @param type this is the type of the root element expected
      * @param node this is the node map used to resolve an override
      * @param map this is used to maintain contextual information
      * 
      * @return the value that should be used to describe the instance
      * 
      * @throws Exception thrown if the class cannot be resolved
      */
     Value read(Type type, NodeMap<InputNode> node, Map map) throws Exception;
  
     /**
      * This is used to attach attribute values to the given node
      * map during the serialization process. This method allows
      * the strategy to augment the XML document so that it can be
      * deserialized using a similar strategy. For example the 
      * default strategy adds a "class" attribute to the node map.
      *  
      * @param type this is the declared class for the field used
      * @param value this is the instance variable being serialized
      * @param node this is the node map used to represent the value
      * @param map this is used to maintain contextual information
      * 
      * @return this returns true if serialization is complete    
      * 
      * @throws Exception thrown if the details cannot be set
      */
     boolean write(Type type, Object value, NodeMap<OutputNode> node, Map map) throws Exception;
  
  }
  