content: /*
   * OverrideValue.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.core;
  
  import com.aliyun.odps.simpleframework.xml.strategy.Value;
  
  /**
   * The <code>OverrideValue</code> is used to represent a value that
   * contains an override type. Providing a value in this way ensures
   * that should an XML element not contain any data representing
   * the type of object then the type data can be provided.
   * 
   * @author Niall Gallagher
   */
  class OverrideValue implements Value {
     
     /**
      * This is the value that is used internally for this value.
      */
     private final Value value;
     
     /**
      * This is the type that is used to represent the value.
      */
     private final Class type;
     
     /**
      * Constructor for the <code>OverrideValue</code> object. This
      * will delegate to an internal value instance but will provide
      * the declared type when requested. 
      * 
      * @param value this is the value that this will delegate to
      * @param type this is the override type for this value
      */
     public OverrideValue(Value value, Class type){
        this.value = value;
        this.type = type;
     }
  
     /**
      * This method is used to acquire an instance of the type that
      * is defined by this object. If the value has not been set
      * then this method will return null if this is not a reference.
      * 
      * @return an instance of the type this object represents
      */
     public Object getValue() {
        return value.getValue();
     }
  
     /**
      * 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 for consistency. 
      * 
      * @param instance this is the value to insert as the type
      */
     public void setValue(Object instance) {
        value.setValue(instance);
     }
  
     /**
      * 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() {
        return type;
     }
  
     /**
      * This returns the length of the array that is to be allocated.
      * If this value does not represent an array then this should
      * return zero to indicate that it is not an array object.
      * 
      * @return this returns the number of elements for the array
      */
     public int getLength() {
        return value.getLength();
     }
  
     /**
      * This will return true if the object represents a reference.
      * A reference will provide a valid instance when this objects 
      * getter is invoked. A valid instance can be a null.
      * 
      * @return this returns true if this represents a reference
      */
     public boolean isReference() {
        return value.isReference();
     }
  }
  