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package uk.org.ury.database;

import java.util.Map;

import uk.org.ury.database.exceptions.MissingPropertyException;


/**
 * An abstract class presenting a template for objects serving as 
 * a data structure for collections of properties retrieved from 
 * a SQL database.
 *
 * @param E  The enumeration type used as the property list.
 * 
 * @param T  The type of datum stored for each property.
 * 
 * @author   Matt Windsor
 */

public abstract class DatabaseItem<E, T>
{
  private Map<E, T> properties;
  
  /**
   * Construct a new item from an existing list of properties.
   * 
   * @param properties  The map of properties that the new item will 
   *                    inherit.
   */
  
  public
  DatabaseItem (Map<E, T> properties)
  {
    this.properties = properties;
  }
  
  
  /**
   * Check whether a property has been set in the item.
   * 
   * @return  true if the property has been set; false otherwise.
   */
  
  public boolean
  has (E property)
  {
    return properties.containsKey (property);
  }
  
  
  /**
   * Query this item for a property.
   * 
   * @param property  The property to query.
   * 
   * @return          The property, if it exists.
   * 
   * @throws          MissingPropertyException if the property does 
   *                  not exist.
   */
  
  public T
  get (E property) throws MissingPropertyException
  {
    if (properties.containsKey (property))
      return properties.get (property);
    else
      throw new MissingPropertyException (property.toString ());
  }
}