content: /*
   * Element.java July 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;
  
  import java.lang.annotation.RetentionPolicy;
  import java.lang.annotation.Retention;
  
  /**
   * The <code>Element</code> annotation is used to represent a field
   * or method that appears as an XML element. Fields or methods that
   * are annotated with this can be either primitive or compound, that
   * is, represent an object that can be serialized and deserialized.
   * Below is an example of the serialized format for a compound object.
   * <p>
   * If this annotates a type that contains no XML annotations then
   * this will look for a suitable <code>Transform</code> for the type
   * using the <code>Transformer</code>. For instance, all primitives 
   * and primitive arrays that are annotated with this will make use 
   * of a transform in order to convert its value to and from suitable 
   * XML representations.
   * <pre>
   * 
   *    &lt;example class="demo.Example"&gt;
   *       &lt;data/&gt;
   *    &lt;example&gt;
   * 
   * </pre>
   * Each element may have any number of attributes and sub-elements
   * representing fields or methods of that compound object. Attribute
   * and element names can be acquired from the annotation or, if the
   * annotation does not explicitly declare a name, it is taken from
   * the annotated field or method. There are exceptions in some cases,
   * for example, the <code>class</code> attribute is reserved by the
   * serialization framework to represent the serialized type. 
   * 
   * @author Niall Gallagher
   */ 
  @Retention(RetentionPolicy.RUNTIME)
  public @interface Element {
     
     /**
      * This represents the name of the XML element. Annotated fields
      * can optionally provide the name of the element. If no name is
      * provided then the name of the annotated field or method will
      * be used in its place. The name is provided if the field or
      * method name is not suitable as an XML element name.
      * 
      * @return the name of the XML element this represents
      */
     String name() default "";
     
     /**
      * This is used to determine whether the element data is written
      * in a CDATA block or not. If this is set to true then the text
      * is written within a CDATA block, by default the text is output
      * as escaped XML. Typically this is useful for primitives only.
      * 
      * @return true if the data is to be wrapped in a CDATA block
      */
     boolean data() default false;
     
     /**
      * Determines whether the element is required within the XML
      * document. Any field marked as not required will not have its
      * value set when the object is deserialized. If an object is to
      * be serialized only a null attribute will not appear as XML.
      * 
      * @return true if the element is required, false otherwise
      */
     boolean required() default true; 
     
     /**
      * This represents an explicit type that should be used for the
      * annotated field or method. Typically this is used when the
      * element forms part of a union group. It allows the union
      * to distinguish the annotation to use based on the type.
      * 
      * @return this returns the explicit type to use for this
      */
     Class type() default void.class;
  }
  