content: /*
   * Value.java January 2007
   *
   * Copyright (C) 2007, 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>Value</code> object describes a type that is represented 
   * by an XML element. This enables a <code>Strategy</code> to define
   * not only the type an element represents, but also defines if that
   * type needs to be created. This allows arrays as well as standard
   * object types to be described. When instantiated the instance should
   * be set on the value object for use by the strategy to detect cycles.
   * 
   * @author Niall Gallagher
   * 
   * @see Strategy
   */
  public interface Value {
  
     /**
      * 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
      */
     Object 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 value this is the value to insert as the type
      */
     void setValue(Object value);
     
     /**
      * 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
      */
     Class getType();
     
     /**
      * 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
      */
     int 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
      */
     boolean isReference();
  }
  