content: /*
   * Reference.java January 2010
   *
   * Copyright (C) 2010, 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.convert;
  
  import com.aliyun.odps.simpleframework.xml.strategy.Value;
  
  /**
   * The <code>Reference</code> object represents a value that holds
   * an object instance. If an object instance is to be provided from
   * a <code>Strategy</code> implementation it must be wrapped in a 
   * value object. The value object can then provide the details of
   * the instance and the actual object instance to the serializer.
   * 
   * @author Niall Gallagher
   */
  class Reference implements Value {
     
     /**
      * This represents the original value returned from a strategy.
      */
     private Value value;
     
     /**
      * This represents the object instance that this represents.
      */
     private Object data;
     
     /**
      * This is the actual type of the reference that is represented.
      */
     private Class actual;
     
     /**
      * Constructor for a <code>Reference</code> object. To create
      * this a value and an object instance is required. The value
      * provided may be null, but the instance should be a valid
      * object instance to be used by the serializer.
      * 
      * @param value this is the original value from a strategy
      * @param data this is the object instance that is wrapped
      * @param actual this is the overriding type of the reference
      */
     public Reference(Value value, Object data, Class actual){
        this.actual = actual;
        this.value = value;
        this.data = data;
     }
     
     /**
      * This will return the length of an array reference. Because
      * the value will represent the value itself the length is 
      * never used, as no instance needs to be created.
      * 
      * @return this will always return zero for a reference
      */
     public int getLength() {
        return 0;
     }
     
     /**
      * This is the type of the object instance this represents. The
      * type returned by this is used to instantiate an object which
      * will be set on this value and the internal graph maintained.
      * 
      * @return the type of the object that must be instantiated
      */
     public Class getType() {
        if(data != null) {
           return data.getClass();
        }
        return actual;
     }
     
     /**
      * This returns the actual object instance that is held by this
      * reference object.
      */
     public Object getValue() {
        return data;
     }
     
     /**
      * This will always return true as this <code>Value</code> object
      * will always contain an object instance. Returning true from 
      * this method tells the serializer that there is no need to
      * actually perform any further deserialization.
      * 
      * @return this always returns true as this will be a reference
      */
     public boolean isReference() {
        return true;
     }
     
     /**
      * This is used to set the value of the object. If the internal
      * <code>Value</code> is not null then the internal value will 
      * have the instance set also. 
      * 
      * @param data this is the object instance that is to be set
      */
     public void setValue(Object data) {
        if(value != null) {
           value.setValue(data);
        }
        this.data = data;
     }
  }