content: /*
   * Reference.java May 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;
  
  /**
   * The <code>Reference</code> object represents an object that 
   * is used to provide a reference to an already instantiated value.
   * This is what is used if there is a cycle in the object graph. 
   * The <code>getValue</code> method of this object will simply
   * return the object instance that was previously created.
   * 
   * @author Niall Gallagher
   */
  class Reference implements Value {
     
     /**
      * This is the object instance that has already be created.
      */
     private Object value;
     
     /**
      * This is the type of the object that this references.
      */
     private Class type;
     
     /**
      * Constructor for the <code>Reference</code> object. This 
      * is used to create a value that will produce the specified 
      * value when the <code>getValue</code> method is invoked.
      * 
      * @param value the value for the reference this represents
      * @param type this is the type value for the instance
      */
     public Reference(Object value, Class type) {      
        this.value = value;      
        this.type = type;
     }
     
     /**
      * This is used to acquire a reference to the instance that is
      * taken from the created object graph. This enables any cycles
      * in the graph to be reestablished from the persisted XML.
      * 
      * @return this returns a reference to the created instance
      */
     public Object getValue() {     
        return value;      
     }
     
     /**
      * This method is used set the value within this object. Once
      * this is set then the <code>getValue</code> method will return
      * the object that has been provided. Typically this will not 
      * be set as this represents a reference value.
      * 
      * @param value this is the value to insert as the type
      */
     public void setValue(Object value) {
        this.value = value;
     }
     
     /**
      * This returns the type for the object that this references.
      * This will basically return the <code>getClass</code> class
      * from the referenced instance. This is used to ensure that
      * the type this represents is compatible to the object field.
      * 
      * @return this returns the type for the referenced object
      */
     public Class getType() {
        return type;
     }
     
     /**
      * This returns zero as this is a reference and will typically
      * not be used to instantiate anything. If the reference is an
      * an array then this can not be used to instantiate it.
      * 
      * @return this returns zero regardless of the value type
      */
     public int getLength() {
        return 0;
     }
     
     /**
      * This always returns true for this object. This indicates to
      * the deserialization process that there should be not further
      * deserialization of the object from the XML source stream.
      * 
      * @return because this is a reference this is always true 
      */
     public boolean isReference() {      
        return true;
     }
  }
  