Using Java 1.8, Spring Boot, JPA, I create a Spring Boot Microservice, where the data model (entity relationship) follows this particular one to many relationship:
Owner can have many Cars.
Cars only have one Owner.
This Spring Boot Microservice has the following functionality:
HTTP GET Endpoints:
- Obtain data about a particular Owner (name, address, etc.) from database.
- Retrieve information about a particular Owner's car (make, model etc.) from database.
HTTP POST Endpoints:
- Persist data about a Owner into database.
- Persist data about a Owner’s Car into database.
These all work when I run the Spring Boot Microservice and manually create Owners & their Cars and also, retrieve them using my GET method endpoints.
What I am trying to do now is to have these be populated when the Spring Boot Microservice loads up (that way, I can start writing unit and integration tests before the Maven build completes).
So, for this I created the following file:
@Component
public class DataInserter implements ApplicationListener<ContextRefreshedEvent> {
@Value("classpath:data/owners.json")
Resource ownersResource;
@Value("classpath:data/cars.json")
Resource carsResource;
@Autowired
private OwnerService ownerService;
@Autowired
private CarsService carService;
@Override
public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
List<Owner> populatedOwners = new ArrayList<>();
try {
Owner aOwner;
File ownersFile = ownersResource.getFile();
File carsFile = carsResource.getFile();
String ownersString = new String(Files.readAllBytes(ownersFile.toPath()));
String carsString = new String(Files.readAllBytes(carsFile.toPath()));
ObjectMapper mapper = new ObjectMapper();
List<Owner> owners = Arrays.asList(mapper.readValue(ownersString, Owner[].class));
List<ElectricCars> cars = Arrays.asList(mapper.readValue(carsString, ElectricCars[].class));
// Populate owners one by one
for (Owner owner : owners) {
aOwner = new Owner(owner.getName(), owner.getAddress(), owner.getCity(), owner.getState(), owner.getZipCode());
ownerService.createOwner(aOwner);
populatedOwners.add(aOwner);
}
// Populate owner cars one by one
for (int i = 0; i < populatedOwners.size(); i++) {
carService.createCars(populatedOwners.get(i).getId(), cars.get(i));
}
// Provide some owners with multiple cars
// carService.createCars(populatedOwners.get(0).getId(), cars.get(3));
// carService.createCars(populatedOwners.get(0).getId(), cars.get(4));
// carService.createCars(populatedOwners.get(1).getId(), cars.get(3));
}
catch(IOException ioe) {
ioe.printStackTrace();;
}
}
}
src/main/resources/data/cars.json:
[
{
"make": "Honda",
"model": "Accord",
"year": "2020"
},
{
"make": "Nissan",
"model": "Maxima",
"year": "2019"
},
{
"make": "Toyota",
"model": "Prius",
"year": "2015"
},
{
"make": "Porsche",
"model": "911",
"year": "2017"
},
{
"make": "Hyundai",
"model": "Elantra",
"year": "2018"
},
{
"make": "Volkswagen",
"model": "Beatle",
"year": "1973"
},
{
"make": "Ford",
"model": "F-150",
"year": "2010"
},
{
"make": "Chevrolet",
"model": "Silverado",
"year": "2020"
},
{
"make": "Toyota",
"model": "Camary",
"year": "2018"
},
{
"make": "Alfa",
"model": "Romeo",
"year": "2017"
}
]
src/main/resources/data/owners.json:
[
{
"name": "Tom Brady"
},
{
"name": "Kobe Bryant"
},
{
"name": "Mike Tyson"
},
{
"name": "Scottie Pippen"
},
{
"name": "John Madden"
},
{
"name": "Arnold Palmer"
},
{
"name": "Tiger Woods"
},
{
"name": "Magic Johnson"
},
{
"name": "George Foreman"
},
{
"name": "Charles Barkley"
}
]
So, when I run this with the following lines commented out:
// Populate owner cars one by one
for (int i = 0; i < populatedOwners.size(); i++) {
carService.createCars(populatedOwners.get(i).getId(), cars.get(i));
}
// Provide some owners with multiple cars
// carService.createCars(populatedOwners.get(0).getId(), cars.get(3));
// carService.createCars(populatedOwners.get(0).getId(), cars.get(4));
// carService.createCars(populatedOwners.get(1).getId(), cars.get(3));
And then I call my Get All Owners REST Endpoint (see below):
GET http://localhost:8080/car-api/owners
JSON Payload yields correctly (each individual owner has a single car):
[
{
"id": 1,
"name": "Tom Brady",
"cars": [
{
"id": 1,
"make": "Honda",
"model": "Accord",
"year": "2020"
}
]
},
{
"id": 2,
"name": "Kobe Bryant",
"cars": [
{
"id": 2,
"make": "Nissan",
"model": "Maxima",
"year": "2019"
}
]
},
{
"id": 3,
"name": "Mike Tyson",
"cars": [
{
"id": 3,
"make": "Toyota",
"model": "Prius",
"year": "2015"
}
]
},
{
"id": 4,
"name": "Scottie Pippen",
"cars": [
{
"id": 4,
"make": "Porsche",
"model": "911",
"year": "2017"
}
]
},
{
"id": 5,
"name": "John Madden",
"cars": [
{
"id": 5,
"make": "Hyundai",
"model": "Elantra",
"year": "2018"
}
]
},
{
"id": 6,
"name": "Arnold Palmer",
"cars": [
{
"id": 6,
"make": "Volkswagen",
"model": "Beatle",
"year": "1973"
}
]
},
{
"id": 7,
"name": "Tiger Woods",
"cars": [
{
"id": 7,
"make": "Ford",
"model": "F-150",
"year": "2010"
}
]
},
{
"id": 8,
"name": "Magic Johnson",
"cars": [
{
"id": 8,
"make": "Chevrolet",
"model": "Silverado",
"year": "2020"
}
]
},
{
"id": 9,
"name": "George Foreman",
"cars": [
{
"id": 9,
"make": "Toyota",
"model": "Camary",
"year": "2018"
}
]
},
{
"id": 10,
"name": "Charles Barkley",
"cars": [
{
"id": 10,
"make": "Alfa",
"model": "Romeo",
"year": "2017"
}
]
}
]
However, when I try to assign more cars to individual owners (it seems this this causes other owner's cars JSON array to become empty):
// Populate owner cars one by one
for (int i = 0; i < populatedOwners.size(); i++) {
carService.createCars(populatedOwners.get(i).getId(), cars.get(i));
}
// Provide some owners with multiple cars
carService.createCars(populatedOwners.get(0).getId(), cars.get(3));
carService.createCars(populatedOwners.get(0).getId(), cars.get(4));
carService.createCars(populatedOwners.get(1).getId(), cars.get(3));
JSON Payload yield the following:
[
{
"id": 1,
"name": "Tom Brady",
"cars": [
{
"id": 1,
"make": "Honda",
"model": "Accord",
"year": "2020"
},
{
"id": 5,
"make": "Hyundai",
"model": "Elantra",
"year": "2018"
}
]
},
{
"id": 2,
"name": "Kobe Bryant",
"cars": [
{
"id": 2,
"make": "Nissan",
"model": "Maxima",
"year": "2019"
},
{
{
"id": 4,
"make": "Porsche",
"model": "911",
"year": "2017"
}
]
},
{
"id": 3,
"name": "Mike Tyson",
"cars": [
{
"id": 3,
"make": "Toyota",
"model": "Prius",
"year": "2015"
}
]
},
{
"id": 4,
"name": "Scottie Pippen",
"cars": []
},
{
"id": 5,
"name": "John Madden",
"cars": []
},
{
"id": 6,
"name": "Arnold Palmer",
"cars": [
{
"id": 6,
"make": "Volkswagen",
"model": "Beatle",
"year": "1973"
}
]
},
{
"id": 7,
"name": "Tiger Woods",
"cars": [
{
"id": 7,
"make": "Ford",
"model": "F-150",
"year": "2010"
}
]
},
{
"id": 8,
"name": "Magic Johnson",
"cars": [
{
"id": 8,
"make": "Chevrolet",
"model": "Silverado",
"year": "2020"
}
]
},
{
"id": 9,
"name": "George Foreman",
"cars": [
{
"id": 9,
"make": "Toyota",
"model": "Camary",
"year": "2018"
}
]
},
{
"id": 10,
"name": "Charles Barkley",
"cars": [
{
"id": 10,
"make": "Alfa",
"model": "Romeo",
"year": "2017"
}
]
}
]
As you can see, it seems like these cars were added to Tom Brady and Kobey Bryant's JSON array of cars but removed from the people who had them (Scottie Pippen & John Madden now have empty JSON arrays of cars)...
Why is this happening, is this a possible bug with my CarServiceImpl.createCar() method?
pom.xml:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.5.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.myapi</groupId>
<artifactId>car-api</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>car-api</name>
<description>Car REST API</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
src/main/resources/applications.properties:
server.servlet.context-path=/car-api
server.port=8080
server.error.whitelabel.enabled=false
# Database specific
spring.jpa.hibernate.ddl-auto=create
spring.datasource.url=jdbc:mysql://localhost:3306/car_db?useSSL=false
spring.datasource.ownername=root
spring.datasource.password=
Owner entity:
@Entity
@Table(name = "owner")
public class Owner {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@NotNull
private String name;
@OneToMany(cascade = CascadeType.ALL,
fetch = FetchType.EAGER,
mappedBy = "owner")
private List<Car> cars = new ArrayList<>();
public Owner() {
}
// Getter & Setters omitted for brevity.
}
Car entity:
@Entity
@Table(name="car")
public class Car {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
String make;
String model;
String year;
@JsonIgnore
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "owner_id", nullable = false)
private Owner owner;
// Getter & Setters omitted for brevity.
}
OwnerRepository:
@Repository
public interface OwnerRepository extends JpaRepository<Owner, Long> {
}
CarRepository:
@Repository
public interface CarRepository extends JpaRepository<Car, Long> {
}
OwnerService:
public interface OwnerService {
boolean createOwner(Owner owner);
Owner getOwnerByOwnerId(Long ownerId);
List<Owner> getAllOwners();
}
OwnerServiceImpl:
@Service
public class OwnerServiceImpl implements OwnerService {
@Autowired
OwnerRepository ownerRepository;
@Autowired
CarRepository carRepository;
@Override
public List<Owner> getAllOwners() {
return ownerRepository.findAll();
}
@Override
public boolean createOwner(Owner owner) {
boolean created = false;
if (owner != null) {
ownerRepository.save(owner);
created = true;
}
return created;
}
@Override
public Owner getOwnerByOwnerId(Long ownerId) {
Optional<Owner> owner = null;
if (ownerRepository.existsById(ownerId)) {
owner = ownerRepository.findById(ownerId);
}
return owner.get();
}
}
CarService:
public interface CarService {
boolean createCar(Long ownerId, Car car);
}
CarServiceImpl:
@Service
public class CarServiceImpl implements CarService {
@Autowired
OwnerRepository ownerRepository;
@Autowired
CarRepository carRepository;
@Override
public boolean createCar(Long ownerId, Car car) {
boolean created = false;
if (ownerRepository.existsById(ownerId)) {
Optional<Owner> owner = ownerRepository.findById(ownerId);
if (owner != null) {
List<Car> cars = owner.get().getCars();
cars.add(car);
owner.get().setCars(cars);
car.setOwner(owner.get());
carRepository.save(car);
created = true;
}
}
return created;
}
}
OwnerController:
@RestController
public class OwnerController {
private HttpHeaders headers = null;
@Autowired
OwnerService ownerService;
public OwnerController() {
headers = new HttpHeaders();
headers.add("Content-Type", "application/json");
}
@RequestMapping(value = { "/owners" }, method = RequestMethod.POST, produces = "APPLICATION/JSON")
public ResponseEntity<Object> createOwner(@Valid @RequestBody Owner owner) {
boolean isCreated = ownerService.createOwner(owner);
if (isCreated) {
return new ResponseEntity<Object>(headers, HttpStatus.OK);
}
else {
return new ResponseEntity<Object>(HttpStatus.NOT_FOUND);
}
}
@RequestMapping(value = { "/owners" }, method = RequestMethod.GET, produces = "APPLICATION/JSON")
public ResponseEntity<Object> getAllOwners() {
List<Owner> owners = ownerService.getAllOwners();
if (owners.isEmpty()) {
return new ResponseEntity<Object>(HttpStatus.NOT_FOUND);
}
return new ResponseEntity<Object>(owners, headers, HttpStatus.OK);
}
@RequestMapping(value = { "/owners/{ownerId}" }, method = RequestMethod.GET, produces = "APPLICATION/JSON")
public ResponseEntity<Object> getOwnerByOwnerId(@PathVariable Long ownerId) {
if (null == ownerId || "".equals(ownerId)) {
return new ResponseEntity<Object>(HttpStatus.NOT_FOUND);
}
Owner owner = ownerService.getOwnerByOwnerId(ownerId);
return new ResponseEntity<Object>(owner, headers, HttpStatus.OK);
}
}
CarController:
@RestController
public class CarController {
private HttpHeaders headers = null;
@Autowired
CarService carService;
public CarController() {
headers = new HttpHeaders();
headers.add("Content-Type", "application/json");
}
@RequestMapping(value = { "/cars/{ownerId}" }, method = RequestMethod.POST, produces = "APPLICATION/JSON")
public ResponseEntity<Object> createCarBasedOnOwnerId(@Valid @RequestBody Car car, Long ownerId) {
boolean isCreated = carService.createCar(ownerId, car);
if (isCreated) {
return new ResponseEntity<Object>(headers, HttpStatus.OK);
}
else {
return new ResponseEntity<Object>(HttpStatus.NOT_FOUND);
}
}
Question(s):
Why by adding new cars to an Owner's car ArrayList, it removes other Owner's cars (which have the same car.id)?
Noticed how inside Owner.java, I had to make the
FetchType.EAGER:
@OneToMany(cascade = CascadeType.ALL,
fetch = FetchType.EAGER,
mappedBy = "owner")
private List<Car> cars = new ArrayList<>();
When I had it as fetch = FetchType.LAZY it threw the following Exception:
2020-03-08 15:18:13,175 ERROR org.springframework.boot.SpringApplication [main] Application run failed
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.myapi.model.User.cars, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:606)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:218)
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585)
at org.hibernate.collection.internal.AbstractPersistentCollection.write(AbstractPersistentCollection.java:409)
at org.hibernate.collection.internal.PersistentBag.add(PersistentBag.java:407)
at org.hibernate.collection.internal.PersistentBag.add(PersistentBag.java:407)
at com.myapi.service.CarServiceImpl.createCar(CarServiceImpl.java:36)
at com.myapi.bootstrap.DataInserter.onApplicationEvent(DataInserter.java:71)
at com.myapi.bootstrap.DataInserter.onApplicationEvent(DataInserter.java:24)
at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:403)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:360)
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:897)
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.finishRefresh(ServletWebServerApplicationContext.java:162)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:553)
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215)
at com.myapi.CarApplication.main(CarApplication.java:12)
Is this related or a separate issue altogether? Am somewhat new to JPA so am wondering if I need to change the values for cascade = CascadeType.ALL in both entities to something else.
- Is there a better way to populate the database with mock data (perhaps in the unit or integration tests rather than on ApplicationContext load up) for testing purposes?
