content: /*
   * CompositeList.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.core;
  
  import com.aliyun.odps.simpleframework.xml.ElementList;
  import com.aliyun.odps.simpleframework.xml.strategy.Type;
  import com.aliyun.odps.simpleframework.xml.stream.InputNode;
  import com.aliyun.odps.simpleframework.xml.stream.OutputNode;
  import java.util.Collection;
  
  /**
   * The <code>CompositeList</code> object is used to convert an element
   * list to a collection of element entries. This in effect performs a 
   * root serialization and deserialization of entry elements for the
   * collection object. On serialization each objects type must be 
   * checked against the XML annotation entry so that it is serialized
   * in a form that can be deserialized. 
   * <pre>
   *
   *    &lt;list&gt;
   *       &lt;entry attribute="value"&gt;
   *          &lt;text&gt;example text value&lt;/text&gt;
   *       &lt;/entry&gt;
   *       &lt;entry attribute="demo"&gt;
   *          &lt;text&gt;some other example&lt;/text&gt;
   *       &lt;/entry&gt;
   *    &lt;/list&gt;
   * 
   * </pre>
   * For the above XML element list the element <code>entry</code> is
   * contained within the list. Each entry element is thus deserialized
   * as a root element and then inserted into the list. This enables
   * lists to be composed from XML documents. For serialization the
   * reverse is done, each element taken from the collection is written
   * as a root element to the owning element to create the list. 
   * Entry objects do not need to be of the same type.
   * 
   * @author Niall Gallagher
   *
   * @see Traverser
   * @see ElementList
   */ 
  class CompositeList implements Converter {
  
     /**
      * This factory is used to create a suitable collection list.
      */         
     private final CollectionFactory factory;
  
     /**
      * This performs the traversal used for object serialization.
      */ 
     private final Traverser root;
     
     /**
      * This represents the name of the entry elements to write.
      */
     private final String name;
     
     /**
      * This is the entry type for elements within the list.
      */   
     private final Type entry;
     
     /**
      * This is the field or method that has been annotated.
      */
     private final Type type;
  
     /**
      * Constructor for the <code>CompositeList</code> object. This is
      * given the list type and entry type to be used. The list type is
      * the <code>Collection</code> implementation that deserialized
      * entry objects are inserted into. 
      *
      * @param context this is the context object used for serialization
      * @param type this is the collection type for the list used
      * @param entry the entry type to be stored within the list
      */    
     public CompositeList(Context context, Type type, Type entry, String name) {
        this.factory = new CollectionFactory(context, type); 
        this.root = new Traverser(context);      
        this.entry = entry;
        this.type = type;
        this.name = name;
     }
  
     /**
      * This <code>read</code> method will read the XML element list from
      * the provided node and deserialize its children as entry types.
      * This will each entry type is deserialized as a root type, that 
      * is, its <code>Root</code> annotation must be present and the
      * name of the entry element must match that root element name.
      * 
      * @param node this is the XML element that is to be deserialized
      * 
      * @return this returns the item to attach to the object contact
      */ 
     public Object read(InputNode node) throws Exception{
        Instance type = factory.getInstance(node);
        Object list = type.getInstance();
        
        if(!type.isReference()) {
           return populate(node, list);
        }
        return list;      
     }
     
     /**
      * This <code>read</code> method will read the XML element map from
      * the provided node and deserialize its children as entry types.
      * Each entry type must contain a key and value so that the entry 
      * can be inserted in to the map as a pair. If either the key or 
      * value is composite it is read as a root object, which means its
      * <code>Root</code> annotation must be present and the name of the
      * object element must match that root element name.
      * 
      * @param node this is the XML element that is to be deserialized
      * @param result this is the map object that is to be populated
      * 
      * @return this returns the item to attach to the object contact
      */
     public Object read(InputNode node, Object result) throws Exception {
        Instance type = factory.getInstance(node);
        
        if(type.isReference()) {
           return type.getInstance();
        }
        type.setInstance(result);
        
        if(result != null) {
           return populate(node, result);
        }
        return result;
     }
     
     /**
      * This <code>populate</code> method wll read the XML element list 
      * from the provided node and deserialize its children as entry types.
      * This will each entry type is deserialized as a root type, that 
      * is, its <code>Root</code> annotation must be present and the
      * name of the entry element must match that root element name.
      * 
      * @param node this is the XML element that is to be deserialized
      * @param result this is the collection that is to be populated
      * 
      * @return this returns the item to attach to the object contact
      */ 
     private Object populate(InputNode node, Object result) throws Exception {
        Collection list = (Collection) result;                 
        
        while(true) {
           InputNode next = node.getNext();
           Class expect = entry.getType();
          
           if(next == null) {
              return list;
           }
           list.add(root.read(next, expect));
        }
     }      
     
     /**
      * This <code>validate</code> method will validate the XML element 
      * list from the provided node and deserialize its children as entry 
      * types. This takes each entry type and validates it as a root type, 
      * that is, its <code>Root</code> annotation must be present and the
      * name of the entry element must match that root element name.
      * 
      * @param node this is the XML element that is to be validated
      * 
      * @return true if the element matches the XML schema class given 
      */ 
     public boolean validate(InputNode node) throws Exception{
        Instance value = factory.getInstance(node);
        
        if(!value.isReference()) {
           Object result = value.setInstance(null);
           Class type = value.getType();
              
           return validate(node, type);
        }
        return true; 
     }
     
     /**
      * This <code>validate</code> method will validate the XML element 
      * list from the provided node and deserialize its children as entry 
      * types. This takes each entry type and validates it as a root type, 
      * that is, its <code>Root</code> annotation must be present and the
      * name of the entry element must match that root element name.
      * 
      * @param node this is the XML element that is to be validated
      * @param type this is the type to validate against the input node
      * 
      * @return true if the element matches the XML schema class given 
      */ 
     private boolean validate(InputNode node, Class type) throws Exception {
        while(true) {
           InputNode next = node.getNext();
           Class expect = entry.getType();
           
           if(next == null) {
              return true;
           }
           root.validate(next, expect);
        }
     }     
  
     /**
      * This <code>write</code> method will write the specified object
      * to the given XML element as as list entries. Each entry within
      * the given collection must be assignable from the annotated 
      * type specified within the <code>ElementList</code> annotation.
      * Each entry is serialized as a root element, that is, its
      * <code>Root</code> annotation is used to extract the name. 
      * 
      * @param source this is the source collection to be serialized 
      * @param node this is the XML element container to be populated
      */ 
     public void write(OutputNode node, Object source) throws Exception {
        Collection list = (Collection) source;                
        
        for(Object item : list) {
           if(item != null) {
              Class expect = entry.getType();
              Class actual = item.getClass();
  
              if(!expect.isAssignableFrom(actual)) {
                 throw new PersistenceException("Entry %s does not match %s for %s", actual, entry, type);                     
              }
              root.write(node, item, expect, name);
           }
        }
     }
  }
  