content: /*
   * ElementListUnion.java March 2011
   *
   * Copyright (C) 2011, 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;
  
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  
  /**
   * The <code>ElementListUnion</code> annotation is used to describe 
   * fields and methods that can dynamically match a schema class. Each 
   * union can have a number of different XML class schemas matched based 
   * on an XML element name or the instance type. Here a collection of
   * element list annotations can be declared. Each annotation expresses
   * the types the list can accept. Taking the declaration below, if the
   * annotation is inline, the list can take a number of varying types
   * all determined from the XML element name.
   * <pre>
   * 
   *    &#64;ElementListUnion({
   *       &#64;ElementList(entry="x", inline=true, type=X.class),
   *       &#64;ElementList(entry="y", inline=true, type=Y.class),
   *       &#64;ElementList(entry="z", inline=true, type=Z.class)               
   *    })
   *    private List&lt;Code&gt; codes;
   *    
   * </pre>
   * For the above definition the list field can take any of the declared
   * types. On deserialization the name of the element will determine the
   * type that is instantiated and inserted in to the list. When the list
   * is serialized the list entry instance type will determine the name 
   * of the element the instance will serialized as. This provides a 
   * useful means of consume more complicated sources. 
   * 
   * @author Niall Gallagher
   * 
   * @see ElementList
   */
  @Retention(RetentionPolicy.RUNTIME)
  public @interface ElementListUnion {
     
     /**
      * This provides the <code>ElementList</code> annotations that have 
      * been defined for this union. Each element list describes the 
      * XML class schema to use and the name of the XML element. This 
      * allows the serialization process to determine which elements
      * map to the defined types. Also, the types define how the XML
      * is generated for a given instance.     
      * 
      * @return the element lists defined for the union declaration
      */   
     ElementList[] value();
  }
  
  