content: /*
   * CompositeKey.java July 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.core;
  
  import com.aliyun.odps.simpleframework.xml.ElementMap;
  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 com.aliyun.odps.simpleframework.xml.stream.Position;
  import com.aliyun.odps.simpleframework.xml.stream.Style;
  
  /**
   * The <code>CompositeKey</code> object is used to convert an object
   * to an from an XML element. This accepts only composite objects and
   * will throw an exception if the <code>ElementMap</code> annotation
   * is configured to have an attribute key. If a key name is given for
   * the annotation then this will act as a parent element to the 
   * resulting XML element for the composite object. 
   * 
   * @author Niall Gallagher
   * 
   * @see ElementMap
   */
  class CompositeKey implements Converter {
     
     /**
      * This is the context used to support the serialization process.
      */
     private final Context context;
     
     /**
      * This is the traverser used to read and write the composite key.
      */
     private final Traverser root;
     
     /**
      * This is the style used to style the names used for the XML.
      */
     private final Style style;
     
     /**
      * This is the entry object used to provide configuration details.
      */
     private final Entry entry;
     
     /**
      * This represents the type of object the key is written as.
      */
     private final Type type;
        
     /**
      * Constructor for the <code>CompositeKey</code> object. This will
      * create an object capable of reading an writing composite keys
      * from an XML element. This also allows a parent element to be
      * created to wrap the key object if desired.
      * 
      * @param context this is the root context for the serialization
      * @param entry this is the entry object used for configuration
      * @param type this is the type of object the key represents
      */
     public CompositeKey(Context context, Entry entry, Type type) throws Exception {
        this.root = new Traverser(context);
        this.style = context.getStyle();
        this.context = context;
        this.entry = entry;
        this.type = type;
     }
     
     /**
      * This method is used to read the key value from the node. The 
      * value read from the node is resolved using the template filter.
      * If the key value can not be found according to the annotation
      * attributes then null is assumed and returned.
      * 
      * @param node this is the node to read the key value from
      * 
      * @return this returns the value deserialized from the node
      */ 
     public Object read(InputNode node) throws Exception {
        Position line = node.getPosition();
        Class expect = type.getType();
        String name = entry.getKey();
        
        if(name == null) {
           name = context.getName(expect);
        }
        if(entry.isAttribute()) {
           throw new AttributeException("Can not have %s as an attribute for %s at %s", expect, entry, line);
        }
        return read(node, name);
     }
     
     /**
      * This method is used to read the key value from the node. The 
      * value read from the node is resolved using the template filter.
      * If the key value can not be found according to the annotation
      * attributes then null is assumed and returned.
      * 
      * @param node this is the node to read the key value from
      * @param value this is the value to deserialize in to
      * 
      * @return this returns the value deserialized from the node
      * 
      * @throws Exception if value is not null an exception is thrown
      */ 
     public Object read(InputNode node, Object value) throws Exception {
        Position line = node.getPosition();
        Class expect = type.getType();
        
        if(value != null) {
           throw new PersistenceException("Can not read key of %s for %s at %s", expect, entry, line);
        }
        return read(node);
     }
     
     /**
      * This method is used to read the key value from the node. The 
      * value read from the node is resolved using the template filter.
      * If the key value can not be found according to the annotation
      * attributes then null is assumed and returned.
      * 
      * @param node this is the node to read the key value from
      * @param key this is the name of the key wrapper XML element
      * 
      * @return this returns the value deserialized from the node
      */ 
     private Object read(InputNode node, String key) throws Exception {
        String name = style.getElement(key);
        Class expect = type.getType();
        
        if(name != null) {
           node = node.getNext(name);
        }    
        if(node == null) {
           return null;
        }   
        if(node.isEmpty()) {
           return null;
        }
        return root.read(node, expect);
     }
     
     /**
      * This method is used to read the key value from the node. The 
      * value read from the node is resolved using the template filter.
      * If the key value can not be found according to the annotation
      * attributes then null is assumed and the node is valid.
      * 
      * @param node this is the node to read the key value from
      * 
      * @return this returns the value deserialized from the node
      */ 
     public boolean validate(InputNode node) throws Exception { 
        Position line = node.getPosition();
        Class expect = type.getType();
        String name = entry.getKey();
        
        if(name == null) {
           name = context.getName(expect);
        }
        if(entry.isAttribute()) {
           throw new ElementException("Can not have %s as an attribute for %s at %s", expect, entry, line);
        }
        return validate(node, name);
     }
     
     /**
      * This method is used to read the key value from the node. The 
      * value read from the node is resolved using the template filter.
      * If the key value can not be found according to the annotation
      * attributes then null is assumed and the node is valid.
      * 
      * @param node this is the node to read the key value from
      * @param key this is the name of the key wrapper XML element
      * 
      * @return this returns the value deserialized from the node
      */ 
     private boolean validate(InputNode node, String key) throws Exception {
        String name = style.getElement(key);
        InputNode next = node.getNext(name);
        Class expect = type.getType();
        
        if(next == null) {
           return true;
        }
        if(next.isEmpty()) {
           return true;
        }
        return root.validate(next, expect);
     }
     
     /**
      * This method is used to write the value to the specified node.
      * The value written to the node must be a composite object and if
      * the element map annotation is configured to have a key attribute
      * then this method will throw an exception.
      * 
      * @param node this is the node that the value is written to
      * @param item this is the item that is to be written
      */
     public void write(OutputNode node, Object item) throws Exception {
        Class expect = type.getType();
        String key = entry.getKey();
        
        if(entry.isAttribute()) {
           throw new ElementException("Can not have %s as an attribute for %s", expect, entry);
        }
        if(key == null) {
           key = context.getName(expect);
        }      
        String name = style.getElement(key);
        
        root.write(node, item, expect, name);      
     }
  }
  