content: /*
   * Namespace.java July 2008
   *
   * Copyright (C) 2008, 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>Namespace</code> annotation is used to set a namespace
   * on an element or attribute. By annotating a method, field or 
   * class with this annotation that entity assumes the XML namespace
   * provided. When used on a class the annotation describes the
   * namespace that should be used, this however can be overridden by
   * an annotated field or method declaration of that type.
   * <pre>
   *  
   *    &lt;book:book xmlns:book="http://www.example.com/book"&gt;
   *       &lt;author&gt;saurabh&lt;/author&gt;
   *       &lt;title&gt;example title&lt;/title&gt;
   *       &lt;isbn&gt;ISB-16728-10&lt;/isbn&gt;
   *    &lt;/book:book&gt;
   *
   * </pre>
   * In the above XML snippet a namespace has been declared with the
   * prefix "book" and the reference "http://www.example.com/book". If
   * such a namespace is applied to a class, method, or field then 
   * that element will contain the namespace and the element name will
   * be prefixed with a namespace qualifier, which is "book" here.
   * <pre>
   *
   *    &lt;example xmlns="http://www.example.com/root"&gt;
   *       &lt;child&gt;
   *          &lt;text xmlns=""&gt;text element&lt;/text&gt;
   *       &lt;/child&gt;
   *    &lt;/example&gt;
   *
   * </pre>
   * In order for a namespace to be inherited it must be specified as
   * a default namespace. A default namespace is one that does not have
   * a prefix. All elements that do not have an explicit namespace will
   * inherit the last default namespace in scope. For details see
   * <a href='http://www.w3.org/TR/xml-names/#defaulting'>Section 6.2</a>
   * of the namespaces in XML 1.0 specification. To remove the default
   * namespace simply specify a namespace with no prefix or reference,
   * such as the "text" element in the above example.  
   *
   * @author Niall Gallagher
   */ 
  @Retention(RetentionPolicy.RUNTIME)
  public @interface Namespace {
  
     /**
      * This is used to specify the unique reference URI that is used 
      * to define the namespace within the document. This is typically
      * a URI as this is a well know universally unique identifier. 
      * It can be anything unique, but typically should be a unique
      * URI reference. If left as the empty string then this will
      * signify that the anonymous namespace will be used.
      *
      * @return this returns the reference used by this namespace    
      */         
     String reference() default "";
  
     /**
      * This is used to specify the prefix used for the namespace. If
      * no prefix is specified then the reference becomes the default
      * namespace for the enclosing element. This means that all 
      * attributes and elements that do not contain a prefix belong
      * to the namespace declared by this annotation.
      *
      * @return this returns the prefix used for this namespace
      */ 
     String prefix() default "";
  }
  