Make Pet.visits @Transient

In that way the Pet and Visit entities are more modular, and we
don't have to rely on a bit of a hack which is that Hibernate
happily maps Pet to its ID in the entity generation (but fails
if you do it at compile time).

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

@@ -15,6 +15,7 @@
  */
 package org.springframework.samples.petclinic.owner;
 
+import org.springframework.samples.petclinic.visit.VisitRepository;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
 import org.springframework.validation.BindingResult;
@@ -40,10 +41,12 @@ class OwnerController {
 
     private static final String VIEWS_OWNER_CREATE_OR_UPDATE_FORM = "owners/createOrUpdateOwnerForm";
     private final OwnerRepository owners;
+    private VisitRepository visits;
 
 
-    public OwnerController(OwnerRepository clinicService) {
+    public OwnerController(OwnerRepository clinicService, VisitRepository visits) {
         this.owners = clinicService;
+        this.visits = visits;
     }
 
     @InitBinder
@@ -126,7 +129,11 @@ class OwnerController {
     @GetMapping("/owners/{ownerId}")
     public ModelAndView showOwner(@PathVariable("ownerId") int ownerId) {
         ModelAndView mav = new ModelAndView("owners/ownerDetails");
-        mav.addObject(this.owners.findById(ownerId));
+        Owner owner = this.owners.findById(ownerId);
+        for (Pet pet : owner.getPets()) {
+            pet.setVisitsInternal(visits.findByPetId(pet.getId()));
+        }
+        mav.addObject(owner);
         return mav;
     }
 

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

@@ -17,20 +17,19 @@ package org.springframework.samples.petclinic.owner;
 
 import java.time.LocalDate;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.LinkedHashSet;
 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.ManyToOne;
-import javax.persistence.OneToMany;
 import javax.persistence.Table;
+import javax.persistence.Transient;
 
 import org.springframework.beans.support.MutableSortDefinition;
 import org.springframework.beans.support.PropertyComparator;
@@ -61,7 +60,7 @@ public class Pet extends NamedEntity {
     @JoinColumn(name = "owner_id")
     private Owner owner;
 
-    @OneToMany(cascade = CascadeType.ALL, mappedBy = "petId", fetch = FetchType.EAGER)
+    @Transient
     private Set<Visit> visits = new LinkedHashSet<>();
 
     public void setBirthDate(LocalDate birthDate) {
@@ -95,8 +94,8 @@ public class Pet extends NamedEntity {
         return this.visits;
     }
 
-    protected void setVisitsInternal(Set<Visit> visits) {
-        this.visits = visits;
+    protected void setVisitsInternal(Collection<Visit> visits) {
+        this.visits = new LinkedHashSet<>(visits);
     }
 
     public List<Visit> getVisits() {

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

@@ -15,15 +15,20 @@
  */
 package org.springframework.samples.petclinic.owner;
 
+import java.util.Map;
+
+import javax.validation.Valid;
+
 import org.springframework.samples.petclinic.visit.Visit;
 import org.springframework.samples.petclinic.visit.VisitRepository;
 import org.springframework.stereotype.Controller;
 import org.springframework.validation.BindingResult;
 import org.springframework.web.bind.WebDataBinder;
-import org.springframework.web.bind.annotation.*;
-
-import javax.validation.Valid;
-import java.util.Map;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.InitBinder;
+import org.springframework.web.bind.annotation.ModelAttribute;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
 
 /**
  * @author Juergen Hoeller
@@ -62,6 +67,7 @@ class VisitController {
     @ModelAttribute("visit")
     public Visit loadPetWithVisit(@PathVariable("petId") int petId, Map<String, Object> model) {
         Pet pet = this.pets.findById(petId);
+        pet.setVisitsInternal(this.visits.findByPetId(petId));
         model.put("pet", pet);
         Visit visit = new Visit();
         pet.addVisit(visit);