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Gemini is a web framework created by TechEmpower.
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 * Copyright (c) 2018, TechEmpower, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name TechEmpower, Inc. nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL TECHEMPOWER, INC. BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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package com.techempower.data.annotation;

import java.lang.annotation.*;

/**
 * This annotation specifies the "left" class of a CachedRelation. 
 * 
 * 
 *   @Relation
 *   public class UsersToGroups
 *   {
 *     @Left
 *     public User user;
 *     
 *     @Right
 *     public Group group;
 *   }
 * 
 * 
 * The field name, in this case "user" will be used to specify the column name, if your
 * column name in the database is UserId, then your class would look like this
 * 

 * 
 *   @Relation
 *   public class UsersToGroups
 *   {
 *     @Left
 *     public User UserId;
 *     
 *     @Right
 *     public Group group;
 *   }
 * 
 */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Left
{
    /**
     * The database column that stores the identifier for the related entity.
     *
     * @return the database column that stores the identifier for the related
     * entity
     * @see com.techempower.cache.CachedRelation.Builder#leftColumn(String)
     */
    String column() default "";
}