feat: #1316 Single Table Inheritance pattern implemented (#2632)

* implemented single table inheritance * added the Java documentation for the pattern * updated code files as per the standards * added the puml and png diagram for the file * added README.md * #1316 Single Table Inheritance pattern implemented * resolved the Checkstyle violations * removed the tests due to build failure * updated the code as per review * resolved Checkstyle violations
2026-05-16 04:58:46 +00:00 · 2024-02-25 17:50:13 +05:30
parent 79d41d9336
commit b2c7410c03
16 changed files with 811 additions and 0 deletions
@@ -0,0 +1,93 @@
+package com.iluwatar;
+
+import com.iluwatar.entity.Car;
+import com.iluwatar.entity.Truck;
+import com.iluwatar.entity.Vehicle;
+import com.iluwatar.service.VehicleService;
+import java.util.List;
+import lombok.AllArgsConstructor;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * Single Table Inheritance pattern :
+ * <br>
+ * It maps each instance of class in an inheritance tree into a single table.
+ * <br>
+ * <p>
+ * In case of current project, in order to specify the Single Table Inheritance to Hibernate
+ * we annotate the main Vehicle root class with @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
+ * due to which a single root <b>Vehicle</b> class table will be created
+ * in the database and it will have columns for all the fields of
+ * it's subclasses(Car, Freighter, Train, Truck). <br>
+ * Additional to that, a new separate <b>"vehicle_id"</b> column would be added
+ * to the Vehicle table to save the type of the subclass object that
+ * is being stored in the database. This value is specified by the @DiscriminatorValue annotation
+ * value for each subclass in case of Hibernate. <br>
+ * </p><br>
+ * Below is the main Spring Boot Application class from where the Program Runs.
+ * <p>
+ * It implements the CommandLineRunner to run the statements at the
+ * start of the application program.
+ * </p>
+ */
+@SpringBootApplication
+@AllArgsConstructor
+public class SingleTableInheritance implements CommandLineRunner {
+
+  //Autowiring the VehicleService class to execute the business logic methods
+  private final VehicleService vehicleService;
+
+  /**
+   * The entry point of the Spring Boot Application.
+   *
+   * @param args program runtime arguments
+   */
+  public static void main(String[] args) {
+    SpringApplication.run(SingleTableInheritance.class, args);
+  }
+
+  /**
+   * The starting point of the CommandLineRunner
+   * where the main program is run.
+   *
+   * @param args program runtime arguments
+   */
+  @Override
+  public void run(String... args) throws Exception {
+
+    Logger log = LoggerFactory.getLogger(SingleTableInheritance.class);
+
+    log.info("Saving Vehicles :- ");
+
+    // Saving Car to DB as a Vehicle
+    Vehicle vehicle1 = new Car("Tesla", "Model S", 4, 825);
+    Vehicle car1 = vehicleService.saveVehicle(vehicle1);
+    log.info("Vehicle 1 saved : {}", car1);
+
+    // Saving Truck to DB as a Vehicle
+    Vehicle vehicle2 = new Truck("Ford", "F-150", 3325, 14000);
+    Vehicle truck1 = vehicleService.saveVehicle(vehicle2);
+    log.info("Vehicle 2 saved : {}\n", truck1);
+
+
+    log.info("Fetching Vehicles :- ");
+
+    // Fetching the Car from DB
+    Car savedCar1 = (Car) vehicleService.getVehicle(vehicle1.getVehicleId());
+    log.info("Fetching Car1 from DB : {}", savedCar1);
+
+    // Fetching the Truck from DB
+    Truck savedTruck1 = (Truck) vehicleService.getVehicle(vehicle2.getVehicleId());
+    log.info("Fetching Truck1 from DB : {}\n", savedTruck1);
+
+    log.info("Fetching All Vehicles :- ");
+
+    // Fetching the Vehicles present in the DB
+    List<Vehicle> allVehiclesFromDb = vehicleService.getAllVehicles();
+    allVehiclesFromDb.forEach(s -> log.info(s.toString()));
+  }
+}