Spring JPA and Inheritance: Dungeons and Dragons Edition

In this exercise, you will practice different strategies of inheritance using Spring JPA in the context of a Dungeons and Dragons game. You will work with entities representing characters and items in the game.

Instructions

1. Set up a new Spring Boot project with the necessary dependencies for Spring JPA and a database of your choice (e.g., H2, MySQL).

2. Create the following entity classes:

   • Character (abstract base class)
     • id (Long)
     • name (String)
     • level (int)
     • attack() (abstract method)
   • Player (extends Character)
     • characterClass (String)
     • race (String)
     • Implement the attack() method specific to players
   • Monster (extends Character)
     • monsterType (String)
     • hitPoints (int)
     • Implement the attack() method specific to monsters
   • Item (abstract base class)
     • id (Long)
     • name (String)
     • use() (abstract method)
   • Weapon (extends Item)
     • damage (int)
     • weaponType (String)
     • Implement the use() method specific to weapons
   • Armor (extends Item)
     • defense (int)
     • armorType (String)
     • Implement the use() method specific to armor

3. Implement the following inheritance strategies:

   • Use the joined table strategy for the Character entity hierarchy (Player and Monster).
   • Use the single table strategy for the Item entity hierarchy (Weapon and Armor).

4. Create repository interfaces for each entity using Spring Data JPA.

5. Create a CharacterService class with the following methods:

   • createPlayer(String name, String characterClass, String race, int level): Creates and save a new player character.
   • createMonster(String name, String monsterType, int hitPoints, int level): Creates and save new monster character.
   • equipWeapon(Long characterId, Long weaponId): Equips a weapon to a character. This method should only log a message saying "Weapon equipped" without modifying the database.
   • equipArmor(Long characterId, Long armorId): Equips armor to a character. This method should only log a message saying "Armor equipped" without modifying the database.
   • attackWithCharacter(Long characterId): Invokes the attack() method of a character.

   The CharacterService class should use the repository interfaces to persist and retrieve data from the database.

6. Create a DataLoader class that implements the CommandLineRunner interface. In the run() method, use the CharacterService to perform the following actions:

   • Create a few player characters and monster characters.
   • Create a few weapons and armor pieces.
   • Equip weapons and armor to characters. This should only result in logging messages.
   • Invoke the attack() method of characters.

Additional Tasks

• Implement a SpecialAbility abstract class with a perform() method, and create subclasses MagicSpell and PhysicalAbility that extend SpecialAbility. Use the table-per-class strategy for this hierarchy.
• Extend the CharacterService to include methods for assigning special abilities to characters and invoking their perform() methods.

Embark on this coding adventure and may your inheritance strategies be victorious!