refactor OwnerRepository:

-<replace>: use `JpaRepository` to replace `Repository` in `OwnerRepository` class.
-<remove1>: remove `save()` method. JpaRepository provides it by default.
-<remove2>: remove `@Query` because in `Owner` class, the `@OneToMany` annotiation achieved `fetch` in query.
-<refactor1>: use `Optional<Owner>` to recieve the result from `findById()`, and if is null, throw `IllegalArugmentExpection`.
-<refactor2>: achieve the assert to judge return value in tests.
-<add>: add name to `@author` tag.

src/main/java/org/springframework/samples/petclinic/model/NamedEntity.java

@@ -25,6 +25,7 @@ import jakarta.validation.constraints.NotBlank;
  *
  * @author Ken Krebs
  * @author Juergen Hoeller
+ * @author Wick Dynex
  */
 @MappedSuperclass
 public class NamedEntity extends BaseEntity {

src/main/java/org/springframework/samples/petclinic/owner/Owner.java

@@ -41,6 +41,7 @@ import jakarta.validation.constraints.NotBlank;
  * @author Sam Brannen
  * @author Michael Isvy
  * @author Oliver Drotbohm
+ * @author Wick Dynex
  */
 @Entity
 @Table(name = "owners")

src/main/java/org/springframework/samples/petclinic/owner/OwnerController.java

@@ -16,6 +16,7 @@
 package org.springframework.samples.petclinic.owner;
 
 import java.util.List;
+import java.util.Optional;
 
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
@@ -40,6 +41,7 @@ import org.springframework.web.servlet.mvc.support.RedirectAttributes;
  * @author Ken Krebs
  * @author Arjen Poutsma
  * @author Michael Isvy
+ * @author Wick Dynex
  */
 @Controller
 class OwnerController {
@@ -59,7 +61,10 @@ class OwnerController {
 
 	@ModelAttribute("owner")
 	public Owner findOwner(@PathVariable(name = "ownerId", required = false) Integer ownerId) {
-		return ownerId == null ? new Owner() : this.owners.findById(ownerId);
+		return ownerId == null ? new Owner()
+				: this.owners.findById(ownerId)
+					.orElseThrow(() -> new IllegalArgumentException("Owner not found with id: " + ownerId
+							+ ". Please ensure the ID is correct " + "and the owner exists in the database."));
 	}
 
 	@GetMapping("/owners/new")
@@ -158,7 +163,9 @@ class OwnerController {
 	@GetMapping("/owners/{ownerId}")
 	public ModelAndView showOwner(@PathVariable("ownerId") int ownerId) {
 		ModelAndView mav = new ModelAndView("owners/ownerDetails");
-		Owner owner = this.owners.findById(ownerId);
+		Optional<Owner> optionalOwner = this.owners.findById(ownerId);
+		Owner owner = optionalOwner.orElseThrow(() -> new IllegalArgumentException(
+				"Owner not found with id: " + ownerId + ". Please ensure the ID is correct "));
 		mav.addObject(owner);
 		return mav;
 	}

src/main/java/org/springframework/samples/petclinic/owner/OwnerRepository.java

@@ -16,12 +16,16 @@
 package org.springframework.samples.petclinic.owner;
 
 import java.util.List;
+import java.util.Optional;
 
+import jakarta.annotation.Nonnull;
+import jakarta.validation.constraints.NotNull;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
+import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.jpa.repository.Query;
-import org.springframework.data.repository.Repository;
 import org.springframework.data.repository.query.Param;
+import org.springframework.lang.NonNullApi;
 import org.springframework.transaction.annotation.Transactional;
 
 /**
@@ -34,8 +38,9 @@ import org.springframework.transaction.annotation.Transactional;
  * @author Juergen Hoeller
  * @author Sam Brannen
  * @author Michael Isvy
+ * @author Wick Dynex
  */
-public interface OwnerRepository extends Repository<Owner, Integer> {
+public interface OwnerRepository extends JpaRepository<Owner, Integer> {
 
 	/**
 	 * Retrieve all {@link PetType}s from the data store.
@@ -52,25 +57,24 @@ public interface OwnerRepository extends Repository<Owner, Integer> {
 	 * @return a Collection of matching {@link Owner}s (or an empty Collection if none
 	 * found)
 	 */
-
 	@Query("SELECT DISTINCT owner FROM Owner owner left join  owner.pets WHERE owner.lastName LIKE :lastName% ")
 	@Transactional(readOnly = true)
 	Page<Owner> findByLastName(@Param("lastName") String lastName, Pageable pageable);
 
 	/**
 	 * Retrieve an {@link Owner} from the data store by id.
+	 * <p>
+	 * This method returns an {@link Optional} containing the {@link Owner} if found. If
+	 * no {@link Owner} is found with the provided id, it will return an empty
+	 * {@link Optional}.
+	 * </p>
 	 * @param id the id to search for
-	 * @return the {@link Owner} if found
+	 * @return an {@link Optional} containing the {@link Owner} if found, or an empty
+	 * {@link Optional} if not found.
+	 * @throws IllegalArgumentException if the id is null (assuming null is not a valid
+	 * input for id)
 	 */
-	@Query("SELECT owner FROM Owner owner left join fetch owner.pets WHERE owner.id =:id")
-	@Transactional(readOnly = true)
-	Owner findById(@Param("id") Integer id);
-
-	/**
-	 * Save an {@link Owner} to the data store, either inserting or updating it.
-	 * @param owner the {@link Owner} to save
-	 */
-	void save(Owner owner);
+	Optional<Owner> findById(@Nonnull Integer id);
 
 	/**
 	 * Returns all the owners from data store

src/main/java/org/springframework/samples/petclinic/owner/Pet.java

@@ -39,6 +39,7 @@ import jakarta.persistence.Table;
  * @author Ken Krebs
  * @author Juergen Hoeller
  * @author Sam Brannen
+ * @author Wick Dynex
  */
 @Entity
 @Table(name = "pets")

src/main/java/org/springframework/samples/petclinic/owner/PetController.java

@@ -17,6 +17,7 @@ package org.springframework.samples.petclinic.owner;
 
 import java.time.LocalDate;
 import java.util.Collection;
+import java.util.Optional;
 
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.ModelMap;
@@ -37,6 +38,7 @@ import org.springframework.web.servlet.mvc.support.RedirectAttributes;
  * @author Juergen Hoeller
  * @author Ken Krebs
  * @author Arjen Poutsma
+ * @author Wick Dynex
  */
 @Controller
 @RequestMapping("/owners/{ownerId}")
@@ -57,8 +59,9 @@ class PetController {
 
 	@ModelAttribute("owner")
 	public Owner findOwner(@PathVariable("ownerId") int ownerId) {
-
-		Owner owner = this.owners.findById(ownerId);
+		Optional<Owner> optionalOwner = this.owners.findById(ownerId);
+		Owner owner = optionalOwner.orElseThrow(() -> new IllegalArgumentException(
+				"Owner not found with id: " + ownerId + ". Please ensure the ID is correct "));
 		if (owner == null) {
 			throw new IllegalArgumentException("Owner ID not found: " + ownerId);
 		}
@@ -73,7 +76,9 @@ class PetController {
 			return new Pet();
 		}
 
-		Owner owner = this.owners.findById(ownerId);
+		Optional<Owner> optionalOwner = this.owners.findById(ownerId);
+		Owner owner = optionalOwner.orElseThrow(() -> new IllegalArgumentException(
+				"Owner not found with id: " + ownerId + ". Please ensure the ID is correct "));
 		if (owner == null) {
 			throw new IllegalArgumentException("Owner ID not found: " + ownerId);
 		}

src/main/java/org/springframework/samples/petclinic/owner/VisitController.java

@@ -16,6 +16,8 @@
 package org.springframework.samples.petclinic.owner;
 
 import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalInt;
 
 import org.springframework.stereotype.Controller;
 import org.springframework.validation.BindingResult;
@@ -35,6 +37,7 @@ import org.springframework.web.servlet.mvc.support.RedirectAttributes;
  * @author Arjen Poutsma
  * @author Michael Isvy
  * @author Dave Syer
+ * @author Wick Dynex
  */
 @Controller
 class VisitController {
@@ -60,7 +63,9 @@ class VisitController {
 	@ModelAttribute("visit")
 	public Visit loadPetWithVisit(@PathVariable("ownerId") int ownerId, @PathVariable("petId") int petId,
 			Map<String, Object> model) {
-		Owner owner = this.owners.findById(ownerId);
+		Optional<Owner> optionalOwner = owners.findById(ownerId);
+		Owner owner = optionalOwner.orElseThrow(() -> new IllegalArgumentException(
+				"Owner not found with id: " + ownerId + ". Please ensure the ID is correct "));
 
 		Pet pet = owner.getPet(petId);
 		model.put("pet", pet);