Additional tweaks in aggregate model.

Introduced Owner.addVisit(…) to avoid that state transition to live in controller code.

Slightly polished some assertions in ClinicServiceTests.

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

@@ -31,6 +31,7 @@ import javax.validation.constraints.NotEmpty;
 
 import org.springframework.core.style.ToStringCreator;
 import org.springframework.samples.petclinic.model.Person;
+import org.springframework.util.Assert;
 
 /**
  * Simple JavaBean domain object representing an owner.
@@ -39,6 +40,7 @@ import org.springframework.samples.petclinic.model.Person;
  * @author Juergen Hoeller
  * @author Sam Brannen
  * @author Michael Isvy
+ * @author Oliver Drotbohm
  */
 @Entity
 @Table(name = "owners")
@@ -149,4 +151,23 @@ public class Owner extends Person {
 				.toString();
 	}
 
+	/**
+	 * Adds the given {@link Visit} to the {@link Pet} with the given identifier.
+	 * @param petId the identifier of the {@link Pet}, must not be {@literal null}.
+	 * @param visit the visit to add, must not be {@literal null}.
+	 */
+	public Owner addVisit(Integer petId, Visit visit) {
+
+		Assert.notNull(petId, "Pet identifier must not be null!");
+		Assert.notNull(visit, "Visit must not be null!");
+
+		Pet pet = getPet(petId);
+
+		Assert.notNull(pet, "Invalid Pet identifier!");
+
+		pet.addVisit(visit);
+
+		return this;
+	}
+
 }

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

@@ -78,13 +78,13 @@ class VisitController {
 	// Spring MVC calls method loadPetWithVisit(...) before processNewVisitForm is
 	// called
 	@PostMapping("/owners/{ownerId}/pets/{petId}/visits/new")
-	public String processNewVisitForm(@ModelAttribute Owner owner, @PathVariable("petId") int petId, @Valid Visit visit,
+	public String processNewVisitForm(@ModelAttribute Owner owner, @PathVariable int petId, @Valid Visit visit,
 			BindingResult result) {
 		if (result.hasErrors()) {
 			return "pets/createOrUpdateVisitForm";
 		}
 		else {
-			owner.getPet(petId).addVisit(visit);
+			owner.addVisit(petId, visit);
 			this.owners.save(owner);
 			return "redirect:/owners/{ownerId}";
 		}

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

@@ -199,13 +199,16 @@ class ClinicServiceTests {
 		Pet pet7 = owner6.getPet(7);
 		int found = pet7.getVisits().size();
 		Visit visit = new Visit();
-		pet7.addVisit(visit);
 		visit.setDescription("test");
+
+		owner6.addVisit(pet7.getId(), visit);
 		this.owners.save(owner6);
 
 		owner6 = this.owners.findById(6);
-		assertThat(pet7.getVisits().size()).isEqualTo(found + 1);
-		assertThat(pet7.getVisits()).allMatch(value -> value.getId() != null);
+
+		assertThat(pet7.getVisits()) //
+				.hasSize(found + 1) //
+				.allMatch(value -> value.getId() != null);
 	}
 
 	@Test
@@ -213,9 +216,10 @@ class ClinicServiceTests {
 		Owner owner6 = this.owners.findById(6);
 		Pet pet7 = owner6.getPet(7);
 		Collection<Visit> visits = pet7.getVisits();
-		assertThat(visits).hasSize(2);
-		Visit[] visitArr = visits.toArray(new Visit[visits.size()]);
-		assertThat(visitArr[0].getDate()).isNotNull();
+
+		assertThat(visits) //
+				.hasSize(2) //
+				.element(0).extracting(Visit::getDate).isNotNull();
 	}
 
 }