diff -r 4f912cd42876 -r 86b5d8a1662f src/main/kotlin/de/uapcore/lightpit/dao/AbstractChildEntityDao.kt
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main/kotlin/de/uapcore/lightpit/dao/AbstractChildEntityDao.kt	Thu Nov 19 13:58:54 2020 +0100
@@ -0,0 +1,64 @@
+/*
+ * Copyright 2020 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 CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package de.uapcore.lightpit.dao
+
+
+abstract class AbstractChildEntityDao<T, P> : AbstractDao<T>() {
+
+    /**
+     * Lists all entities being a child of the specified parent.
+     * @param parent the parent
+     * @return the list of child instances
+     */
+    abstract fun list(parent: P): List<T>
+
+    /**
+     * Finds an entity by its integer ID.
+     * It is not guaranteed that referenced entities are automatically joined.
+     *
+     * @param id the id
+     * @return the entity or null if there is no such entity
+     */
+    abstract fun find(id: Int): T?
+
+    /**
+     * Inserts an instance into database.
+     * It is not guaranteed that generated fields will be updated in the instance.
+     *
+     * @param instance the instance to insert
+     * @param parent a reference to the parent
+     */
+    abstract fun save(instance: T, parent: P)
+
+    /**
+     * Updates an instance in the database.
+     *
+     * @param instance the instance to update
+     * @return true if an instance has been updated, false if the instance is not present in database
+     */
+    abstract fun update(instance: T): Boolean
+}