content: /*
   * MapFilter.java May 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.filter;
  
  import java.util.Map;
  
  /**
   * The <code>MapFilter</code> object is a filter that can make use
   * of user specified mappings for replacement. This filter can be
   * given a <code>Map</code> of name value pairs which will be used
   * to resolve a value using the specified mappings. If there is
   * no match found the filter will delegate to the provided filter. 
   * 
   * @author Niall Gallagher
   */
  public class MapFilter implements Filter {
     
     /**
      * This will resolve the replacement if no mapping is found.
      */
     private Filter filter;        
  
     /**
      * This contains a collection of user specified mappings.
      */
     private Map map;
          
     /**
      * Constructor for the <code>MapFilter</code> object. This will
      * use the specified mappings to resolve replacements. If this
      * map does not contain a requested mapping null is resolved.
      * 
      * @param map this contains the user specified mappings
      */
     public MapFilter(Map map) {
        this(map, null);           
     }
       
     /**
      * Constructor for the <code>MapFilter</code> object. This will
      * use the specified mappings to resolve replacements. If this
      * map does not contain a requested mapping the provided filter
      * is used to resolve the replacement text.
      * 
      * @param map this contains the user specified mappings
      * @param filter this is delegated to if the map fails
      */   
     public MapFilter(Map map, Filter filter) {
        this.filter = filter;  
        this.map = map;      
     }
  
     /**
      * Replaces the text provided with the value resolved from the
      * specified <code>Map</code>. If the map fails this will
      * delegate to the specified <code>Filter</code> if it is not
      * a null object. If no match is found a null is returned.
      * 
      * @param text this is the text value to be replaced
      * 
      * @return this will return the replacement text resolved
      */
     public String replace(String text) {
        Object value = null;
        
        if(map != null) {
           value = map.get(text);
        }
        if(value != null) {
           return value.toString();                       
        }
        if(filter != null) {
           return filter.replace(text);              
        }      
        return null;
     }   
  }
  