src/main/java/de/uapcore/lightpit/dao/GenericDao.java

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2018 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. 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.
 *
 * 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 THE COPYRIGHT HOLDER OR CONTRIBUTORS 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, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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package de.uapcore.lightpit.dao;

import java.sql.SQLException;
import java.util.List;

public interface GenericDao<T> {
    /**
     * Returns a list of all entities.
     *
     * @return a list of all objects
     * @throws SQLException on any kind of SQL errors
     */
    List<T> list() throws SQLException;

    /**
     * Finds an entity by its integer ID.
     *
     * @param id the id
     * @return the enity or null if there is no such entity
     * @throws SQLException on any kind of SQL errors
     */
    T find(int id) throws SQLException;

    /**
     * Inserts an instance into database.
     *
     * @param instance the instance to insert
     * @throws SQLException on any kind of SQL errors
     */
    void save(T instance) throws SQLException;

    /**
     * Updates an instance in the database.
     *
     * @param instance the instance to insert
     * @return true if an instance has been updated, false if no instance with the specified ID was found
     * @throws SQLException on any kind of SQL errors
     */
    boolean update(T instance) throws SQLException;

    /**
     * Inserts or updates an instance in the database.
     * Tries an update first and if that fails, performs a save.
     *
     * @param instance the instance to insert or update
     * @throws SQLException on any kind of SQL errors
     * @see #update(Object)
     * @see #save(Object)
     */
    default void saveOrUpdate(T instance) throws SQLException {
        if (!update(instance)) save(instance);
    }
}