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 @@
  *
  * @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 @@
  * @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 @@
  * @author Ken Krebs
  * @author Arjen Poutsma
  * @author Michael Isvy
+ * @author Wick Dynex
  */
 @Controller
 class OwnerController {
@@ -59,7 +61,10 @@ public void setAllowedFields(WebDataBinder dataBinder) {
 
 	@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 @@ public String processUpdateOwnerForm(@Valid Owner owner, BindingResult result, @
 	@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 @@
  * @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
-	 */
-	@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
+	 * @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)
 	 */
-	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 @@
  * @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 @@
 
 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 @@
  * @author Juergen Hoeller
  * @author Ken Krebs
  * @author Arjen Poutsma
+ * @author Wick Dynex
  */
 @Controller
 @RequestMapping("/owners/{ownerId}")
@@ -57,8 +59,9 @@ public Collection<PetType> populatePetTypes() {
 
 	@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 @@ public Pet findPet(@PathVariable("ownerId") int ownerId,
 			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 @@
  * @author Arjen Poutsma
  * @author Michael Isvy
  * @author Dave Syer
+ * @author Wick Dynex
  */
 @Controller
 class VisitController {
@@ -60,7 +63,9 @@ public void setAllowedFields(WebDataBinder dataBinder) {
 	@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);

src/test/java/org/springframework/samples/petclinic/owner/OwnerControllerTests.java

@@ -31,6 +31,7 @@
 import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
 
 import java.time.LocalDate;
+import java.util.Optional;
 
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.greaterThan;
@@ -52,6 +53,7 @@
  * Test class for {@link OwnerController}
  *
  * @author Colin But
+ * @author Wick Dynex
  */
 @WebMvcTest(OwnerController.class)
 @DisabledInNativeImage
@@ -94,7 +96,7 @@ void setup() {
 
 		given(this.owners.findAll(any(Pageable.class))).willReturn(new PageImpl<>(Lists.newArrayList(george)));
 
-		given(this.owners.findById(TEST_OWNER_ID)).willReturn(george);
+		given(this.owners.findById(TEST_OWNER_ID)).willReturn(Optional.of(george));
 		Visit visit = new Visit();
 		visit.setDate(LocalDate.now());
 		george.getPet("Max").getVisits().add(visit);
@@ -240,7 +242,7 @@ public void testProcessUpdateOwnerFormWithIdMismatch() throws Exception {
 		owner.setCity("New York");
 		owner.setTelephone("0123456789");
 
-		when(owners.findById(pathOwnerId)).thenReturn(owner);
+		when(owners.findById(pathOwnerId)).thenReturn(Optional.of(owner));
 
 		mockMvc.perform(MockMvcRequestBuilders.post("/owners/{ownerId}/edit", pathOwnerId).flashAttr("owner", owner))
 			.andExpect(status().is3xxRedirection())

src/test/java/org/springframework/samples/petclinic/owner/PetControllerTests.java

@@ -46,6 +46,7 @@
  * Test class for the {@link PetController}
  *
  * @author Colin But
+ * @author Wick Dynex
  */
 @WebMvcTest(value = PetController.class,
 		includeFilters = @ComponentScan.Filter(value = PetTypeFormatter.class, type = FilterType.ASSIGNABLE_TYPE))
@@ -79,7 +80,7 @@ void setup() {
 		dog.setId(TEST_PET_ID + 1);
 		pet.setName("petty");
 		dog.setName("doggy");
-		given(this.owners.findById(TEST_OWNER_ID)).willReturn(owner);
+		given(this.owners.findById(TEST_OWNER_ID)).willReturn(Optional.of(owner));
 	}
 
 	@Test

src/test/java/org/springframework/samples/petclinic/owner/VisitControllerTests.java

@@ -32,10 +32,13 @@
 import org.springframework.test.context.aot.DisabledInAotMode;
 import org.springframework.test.web.servlet.MockMvc;
 
+import java.util.Optional;
+
 /**
  * Test class for {@link VisitController}
  *
  * @author Colin But
+ * @author Wick Dynex
  */
 @WebMvcTest(VisitController.class)
 @DisabledInNativeImage
@@ -58,7 +61,7 @@ void init() {
 		Pet pet = new Pet();
 		owner.addPet(pet);
 		pet.setId(TEST_PET_ID);
-		given(this.owners.findById(TEST_OWNER_ID)).willReturn(owner);
+		given(this.owners.findById(TEST_OWNER_ID)).willReturn(Optional.of(owner));
 	}
 
 	@Test

src/test/java/org/springframework/samples/petclinic/service/ClinicServiceTests.java

@@ -20,6 +20,7 @@
 
 import java.time.LocalDate;
 import java.util.Collection;
+import java.util.Optional;
 
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -90,7 +91,9 @@ void shouldFindOwnersByLastName() {
 
 	@Test
 	void shouldFindSingleOwnerWithPet() {
-		Owner owner = this.owners.findById(1);
+		Optional<Owner> optionalOwner = this.owners.findById(1);
+		assertThat(optionalOwner).isPresent();
+		Owner owner = optionalOwner.get();
 		assertThat(owner.getLastName()).startsWith("Franklin");
 		assertThat(owner.getPets()).hasSize(1);
 		assertThat(owner.getPets().get(0).getType()).isNotNull();
@@ -119,15 +122,19 @@ void shouldInsertOwner() {
 	@Test
 	@Transactional
 	void shouldUpdateOwner() {
-		Owner owner = this.owners.findById(1);
+		Optional<Owner> optionalOwner = this.owners.findById(1);
+		assertThat(optionalOwner).isPresent();
+		Owner owner = optionalOwner.get();
 		String oldLastName = owner.getLastName();
 		String newLastName = oldLastName + "X";
 
 		owner.setLastName(newLastName);
 		this.owners.save(owner);
 
 		// retrieving new name from database
-		owner = this.owners.findById(1);
+		optionalOwner = this.owners.findById(1);
+		assertThat(optionalOwner).isPresent();
+		owner = optionalOwner.get();
 		assertThat(owner.getLastName()).isEqualTo(newLastName);
 	}
 
@@ -144,7 +151,10 @@ void shouldFindAllPetTypes() {
 	@Test
 	@Transactional
 	void shouldInsertPetIntoDatabaseAndGenerateId() {
-		Owner owner6 = this.owners.findById(6);
+		Optional<Owner> optionalOwner = this.owners.findById(6);
+		assertThat(optionalOwner).isPresent();
+		Owner owner6 = optionalOwner.get();
+
 		int found = owner6.getPets().size();
 
 		Pet pet = new Pet();
@@ -157,7 +167,9 @@ void shouldInsertPetIntoDatabaseAndGenerateId() {
 
 		this.owners.save(owner6);
 
-		owner6 = this.owners.findById(6);
+		optionalOwner = this.owners.findById(6);
+		assertThat(optionalOwner).isPresent();
+		owner6 = optionalOwner.get();
 		assertThat(owner6.getPets()).hasSize(found + 1);
 		// checks that id has been generated
 		pet = owner6.getPet("bowser");
@@ -167,15 +179,20 @@ void shouldInsertPetIntoDatabaseAndGenerateId() {
 	@Test
 	@Transactional
 	void shouldUpdatePetName() {
-		Owner owner6 = this.owners.findById(6);
+		Optional<Owner> optionalOwner = this.owners.findById(6);
+		assertThat(optionalOwner).isPresent();
+		Owner owner6 = optionalOwner.get();
+
 		Pet pet7 = owner6.getPet(7);
 		String oldName = pet7.getName();
 
 		String newName = oldName + "X";
 		pet7.setName(newName);
 		this.owners.save(owner6);
 
-		owner6 = this.owners.findById(6);
+		optionalOwner = this.owners.findById(6);
+		assertThat(optionalOwner).isPresent();
+		owner6 = optionalOwner.get();
 		pet7 = owner6.getPet(7);
 		assertThat(pet7.getName()).isEqualTo(newName);
 	}
@@ -194,7 +211,10 @@ void shouldFindVets() {
 	@Test
 	@Transactional
 	void shouldAddNewVisitForPet() {
-		Owner owner6 = this.owners.findById(6);
+		Optional<Owner> optionalOwner = this.owners.findById(6);
+		assertThat(optionalOwner).isPresent();
+		Owner owner6 = optionalOwner.get();
+
 		Pet pet7 = owner6.getPet(7);
 		int found = pet7.getVisits().size();
 		Visit visit = new Visit();
@@ -210,7 +230,10 @@ void shouldAddNewVisitForPet() {
 
 	@Test
 	void shouldFindVisitsByPetId() {
-		Owner owner6 = this.owners.findById(6);
+		Optional<Owner> optionalOwner = this.owners.findById(6);
+		assertThat(optionalOwner).isPresent();
+		Owner owner6 = optionalOwner.get();
+
 		Pet pet7 = owner6.getPet(7);
 		Collection<Visit> visits = pet7.getVisits();