Remove manual id management in child entities

This is reverting a workaround for a Hibernate "feature". There's
no need for the child entities (Pet and Visit) to know about their
parent (foreign key). Hibernate can manage that just fine with a
@joincolumn. But it needs a nullable foreign key column in the
DB schema. That's the downside. The upside is much less code in
Java.

Author: Dave Syer

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

@@ -16,22 +16,19 @@
 package org.springframework.samples.petclinic.owner;
 
 import java.util.ArrayList;
-import java.util.Collections;
-import java.util.HashSet;
 import java.util.List;
-import java.util.Set;
 
 import javax.persistence.CascadeType;
 import javax.persistence.Column;
 import javax.persistence.Entity;
 import javax.persistence.FetchType;
+import javax.persistence.JoinColumn;
 import javax.persistence.OneToMany;
+import javax.persistence.OrderBy;
 import javax.persistence.Table;
 import javax.validation.constraints.Digits;
 import javax.validation.constraints.NotEmpty;
 
-import org.springframework.beans.support.MutableSortDefinition;
-import org.springframework.beans.support.PropertyComparator;
 import org.springframework.core.style.ToStringCreator;
 import org.springframework.samples.petclinic.model.Person;
 
@@ -60,8 +57,10 @@ public class Owner extends Person {
 	@Digits(fraction = 0, integer = 10)
 	private String telephone;
 
-	@OneToMany(cascade = CascadeType.ALL, mappedBy = "ownerId", fetch = FetchType.EAGER)
-	private Set<Pet> pets;
+	@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+	@JoinColumn(name = "owner_id")
+	@OrderBy("name")
+	private List<Pet> pets = new ArrayList<>();
 
 	public String getAddress() {
 		return this.address;
@@ -87,28 +86,14 @@ public void setTelephone(String telephone) {
 		this.telephone = telephone;
 	}
 
-	protected Set<Pet> getPetsInternal() {
-		if (this.pets == null) {
-			this.pets = new HashSet<>();
-		}
-		return this.pets;
-	}
-
-	protected void setPetsInternal(Set<Pet> pets) {
-		this.pets = pets;
-	}
-
 	public List<Pet> getPets() {
-		List<Pet> sortedPets = new ArrayList<>(getPetsInternal());
-		PropertyComparator.sort(sortedPets, new MutableSortDefinition("name", true, true));
-		return Collections.unmodifiableList(sortedPets);
+		return this.pets;
 	}
 
 	public void addPet(Pet pet) {
 		if (pet.isNew()) {
-			getPetsInternal().add(pet);
+			getPets().add(pet);
 		}
-		pet.setOwnerId(getId());
 	}
 
 	/**
@@ -126,7 +111,7 @@ public Pet getPet(String name) {
 	 * @return a pet if pet id is already in use
 	 */
 	public Pet getPet(Integer id) {
-		for (Pet pet : getPetsInternal()) {
+		for (Pet pet : getPets()) {
 			if (!pet.isNew()) {
 				Integer compId = pet.getId();
 				if (compId.equals(id)) {
@@ -144,7 +129,7 @@ public Pet getPet(Integer id) {
 	 */
 	public Pet getPet(String name, boolean ignoreNew) {
 		name = name.toLowerCase();
-		for (Pet pet : getPetsInternal()) {
+		for (Pet pet : getPets()) {
 			if (!ignoreNew || !pet.isNew()) {
 				String compName = pet.getName();
 				compName = compName == null ? "" : compName.toLowerCase();

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

@@ -52,17 +52,11 @@ public class Pet extends NamedEntity {
 	@JoinColumn(name = "type_id")
 	private PetType type;
 
-	@Column
-	private Integer ownerId;
-
-	@OneToMany(cascade = CascadeType.ALL, mappedBy = "petId", fetch = FetchType.LAZY)
+	@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
+	@JoinColumn(name = "pet_id")
 	@OrderBy("visit_date ASC")
 	private Set<Visit> visits = new LinkedHashSet<>();
 
-	public void setOwnerId(Integer ownerId) {
-		this.ownerId = ownerId;
-	}
-
 	public void setBirthDate(LocalDate birthDate) {
 		this.birthDate = birthDate;
 	}
@@ -85,7 +79,6 @@ public Collection<Visit> getVisits() {
 
 	public void addVisit(Visit visit) {
 		getVisits().add(visit);
-		visit.setPetId(this.getId());
 	}
 
 }

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

@@ -40,12 +40,8 @@ public class Visit extends BaseEntity {
 	private LocalDate date;
 
 	@NotEmpty
-	@Column
 	private String description;
 
-	@Column
-	private Integer petId;
-
 	/**
 	 * Creates a new instance of Visit for the current date
 	 */
@@ -69,12 +65,4 @@ public void setDescription(String description) {
 		this.description = description;
 	}
 
-	public Integer getPetId() {
-		return this.petId;
-	}
-
-	public void setPetId(Integer petId) {
-		this.petId = petId;
-	}
-
 }

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

@@ -78,12 +78,13 @@ public String initNewVisitForm(@PathVariable("petId") int petId, Map<String, Obj
 	// Spring MVC calls method loadPetWithVisit(...) before processNewVisitForm is
 	// called
 	@PostMapping("/owners/{ownerId}/pets/{petId}/visits/new")
-	public String processNewVisitForm(@ModelAttribute Owner owner, @Valid Visit visit, BindingResult result) {
+	public String processNewVisitForm(@ModelAttribute Owner owner, @PathVariable("petId") int petId, @Valid Visit visit,
+			BindingResult result) {
 		if (result.hasErrors()) {
 			return "pets/createOrUpdateVisitForm";
 		}
 		else {
-			owner.getPet(visit.getPetId()).addVisit(visit);
+			owner.getPet(petId).addVisit(visit);
 			this.owners.save(owner);
 			return "redirect:/owners/{ownerId}";
 		}

src/main/resources/db/h2/schema.sql

@@ -48,15 +48,15 @@ CREATE TABLE pets (
   name       VARCHAR(30),
   birth_date DATE,
   type_id    INTEGER NOT NULL,
-  owner_id   INTEGER NOT NULL
+  owner_id   INTEGER
 );
 ALTER TABLE pets ADD CONSTRAINT fk_pets_owners FOREIGN KEY (owner_id) REFERENCES owners (id);
 ALTER TABLE pets ADD CONSTRAINT fk_pets_types FOREIGN KEY (type_id) REFERENCES types (id);
 CREATE INDEX pets_name ON pets (name);
 
 CREATE TABLE visits (
   id          INTEGER IDENTITY PRIMARY KEY,
-  pet_id      INTEGER NOT NULL,
+  pet_id      INTEGER,
   visit_date  DATE,
   description VARCHAR(255)
 );

src/main/resources/db/hsqldb/schema.sql

@@ -48,15 +48,15 @@ CREATE TABLE pets (
   name       VARCHAR(30),
   birth_date DATE,
   type_id    INTEGER NOT NULL,
-  owner_id   INTEGER NOT NULL
+  owner_id   INTEGER
 );
 ALTER TABLE pets ADD CONSTRAINT fk_pets_owners FOREIGN KEY (owner_id) REFERENCES owners (id);
 ALTER TABLE pets ADD CONSTRAINT fk_pets_types FOREIGN KEY (type_id) REFERENCES types (id);
 CREATE INDEX pets_name ON pets (name);
 
 CREATE TABLE visits (
   id          INTEGER IDENTITY PRIMARY KEY,
-  pet_id      INTEGER NOT NULL,
+  pet_id      INTEGER,
   visit_date  DATE,
   description VARCHAR(255)
 );

src/main/resources/db/mysql/schema.sql

@@ -40,15 +40,15 @@ CREATE TABLE IF NOT EXISTS pets (
   name VARCHAR(30),
   birth_date DATE,
   type_id INT(4) UNSIGNED NOT NULL,
-  owner_id INT(4) UNSIGNED NOT NULL,
+  owner_id INT(4) UNSIGNED,
   INDEX(name),
   FOREIGN KEY (owner_id) REFERENCES owners(id),
   FOREIGN KEY (type_id) REFERENCES types(id)
 ) engine=InnoDB;
 
 CREATE TABLE IF NOT EXISTS visits (
   id INT(4) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
-  pet_id INT(4) UNSIGNED NOT NULL,
+  pet_id INT(4) UNSIGNED,
   visit_date DATE,
   description VARCHAR(255),
   FOREIGN KEY (pet_id) REFERENCES pets(id)

src/main/resources/db/postgres/schema.sql

@@ -38,14 +38,14 @@ CREATE TABLE IF NOT EXISTS pets (
   name       TEXT,
   birth_date DATE,
   type_id    INT NOT NULL REFERENCES types (id),
-  owner_id   INT NOT NULL REFERENCES owners (id)
+  owner_id   INT REFERENCES owners (id)
 );
 CREATE INDEX ON pets (name);
 CREATE INDEX ON pets (owner_id);
 
 CREATE TABLE IF NOT EXISTS visits (
   id          INT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
-  pet_id      INT NOT NULL REFERENCES pets (id),
+  pet_id      INT REFERENCES pets (id),
   visit_date  DATE,
   description TEXT
 );

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

@@ -75,11 +75,11 @@ private Owner george() {
 		Pet max = new Pet();
 		PetType dog = new PetType();
 		dog.setName("dog");
-		max.setId(1);
 		max.setType(dog);
 		max.setName("Max");
 		max.setBirthDate(LocalDate.now());
-		george.setPetsInternal(Collections.singleton(max));
+		george.addPet(max);
+		max.setId(1);
 		return george;
 	};
 
@@ -95,7 +95,6 @@ void setup() {
 		given(this.owners.findById(TEST_OWNER_ID)).willReturn(george);
 		Visit visit = new Visit();
 		visit.setDate(LocalDate.now());
-		visit.setPetId(george.getPet("Max").getId());
 		george.getPet("Max").getVisits().add(visit);
 
 	}

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

@@ -216,7 +216,6 @@ void shouldFindVisitsByPetId() throws Exception {
 		assertThat(visits).hasSize(2);
 		Visit[] visitArr = visits.toArray(new Visit[visits.size()]);
 		assertThat(visitArr[0].getDate()).isNotNull();
-		assertThat(visitArr[0].getPetId()).isEqualTo(7);
 	}
 
 }