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  package org.apache.cayenne.configuration.xml;
  
  import org.apache.cayenne.configuration.ConfigurationNode;
  
  /**
   * <p>
   * Storage for all kind of meta data that is not required for runtime.
   * </p>
   * <p>
   * Currently used by Modeler and cli tools (e.g. Maven, Ant and Gradle) to store project extra data.
   * </p>
   *
   * <p>
   * Usage: <pre>
   *      // attach custom information to data map
   *      metaData.add(dataMap, myObject);
   *
   *      // read data
   *      MyObject obj = metaData.get(dataMap, MyObject.class);
   * </pre>
   * </p>
   *
   * @since 4.1
   */
  public interface DataChannelMetaData {
  
      /**
       * Store data for object.
       *
       * @param key object for which we want to store data
       * @param value data to store
       */
      void add(ConfigurationNode key, Object value);
  
      /**
       *
       * Get meta data for object
       *
       * @param key object for wich we want meta data
       * @param type meta data type class
       * @param <T> meta data type
       * @return value or {@code null} if no data available
       */
      <T> T get(ConfigurationNode key, Class<T> type);
  
      /**
       * @since 4.1
       * @param key object for wich we want meta data
       * @param type meta data type class
       * @param <T> meta data type
       * @return value or {@code null} if no can't remove
       */
      <T> T remove(ConfigurationNode key, Class<T> type);
  }
  