I have the following entity in spring boot application:
#Entity
#Data
#AllArgsConstructor
#NoArgsConstructor
#Audited
#XmlRootElement
#XmlAccessorType(XmlAccessType.NONE)
#Table(name = "currency", catalog = "currency_db")
public class Currency implements java.io.Serializable {
#Autowired
Messages messages;
As for message, it just a container of spring MessageSource here it is:
#ApplicationScope
#Component
#Slf4j
public class Messages {
#Autowired
private MessageSource messageSource;
private MessageSourceAccessor accessor;
#PostConstruct
private void init() {
accessor = new MessageSourceAccessor(messageSource, Locale.ENGLISH);
log.info("Messages initialized");
}
public String get(String code) {
return accessor.getMessage(code);
}
}
I'm getting the following error when run mvn clean install. Any idea what I'm missing here?
org.hibernate.MappingException: Could not determine type for: com.company.currencyservice.Messages, at table: currency, for columns: [org.hibernate.mapping.Column(messages)]
It's looks like hibernate think it's a column. Thanks.
Entities are not Spring beans and therefor you cannot use dependency injection in entities.
If you want to access a Spring bean from within an entity you can use a helper class like this:
#Service
public class ApplicationContextProvider implements ApplicationContextAware {
private static ApplicationContext context;
public static <T> T bean(Class<T> beanType) {
return context.getBean(beanType);
}
public static Object bean(String name) {
return context.getBean(name);
}
#Override
public void setApplicationContext(#SuppressWarnings("NullableProblems") ApplicationContext ac) {
context = ac;
}
}
Then you can use ApplicationContextProvider.getBean(Messages.class) to get access to the Messages.
I am having following code below.
#Builder(toBuilder = true)
#AllArgsConstructor(access = AccessLevel.PRIVATE)
#NoArgsConstructor(access = AccessLevel.PRIVATE)
#ToString
#EqualsAndHashCode
#Configurable
public class Employee {
#Autowired
#Qualifier("findEmpByDepartment")
private Function<Long, Long> empByDepartment;
private void save() {
this.empByDepartment.getList();
}
}
and FindEmpByDepartment class below.
#Component("findEmpByDepartment")
public class FindEmpByDepartment implements Function<Long, Long> {
public void getList() {
}
....
}
My problem is I am always getting null when invoke
this.empByDepartment.getList();
line. Here this.empByDepartment is coming as null. Any idea why it is like this?
Thanks
May be you would have missed annotating any class in the flow hierarchy .
#Service, #Repository and #Controller are all specializations of #Component, so any class you want to auto-wire needs to be annotated with one of them.
IoC is like the cool kid on the block and if you are using Spring then you need to be using it all the time .
So make sure you do not have any object created with new operator in the entire flow .
#Controller
public class Controller {
#GetMapping("/example")
public String example() {
MyService my = new MyService();
my.doStuff();
}
}
#Service
public class MyService() {
#Autowired
MyRepository repo;
public void doStuff() {
repo.findByName( "steve" );
}
}
#Repository
public interface MyRepository extends CrudRepository<My, Long> {
List<My> findByName( String name );
}
This will throw a NullPointerException in the service class when it tries to access the MyRepository auto-wired Repository, not because there is anything wrong with the wiring of the Repository but because you instantiated MyService() manually with MyService my = new MyService().
For more details , you can check
https://www.moreofless.co.uk/spring-mvc-java-autowired-component-null-repository-service/
In normal Spring, when we want to autowire an interface, we define it's implementation in Spring context file.
What about Spring boot?
how can we achieve this?
currently we only autowire classes that are not interfaces.
Another part of this question is about using a class in a Junit class inside a Spring boot project.
If we want to use a CalendarUtil for example, if we autowire CalendarUtil, it will throw a null pointer exception. What can we do in this case? I just initialized using "new" for now...
Use #Qualifier annotation is used to differentiate beans of the same interface
Take look at Spring Boot documentation
Also, to inject all beans of the same interface, just autowire List of interface
(The same way in Spring / Spring Boot / SpringBootTest)
Example below:
#SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
public interface MyService {
void doWork();
}
#Service
#Qualifier("firstService")
public static class FirstServiceImpl implements MyService {
#Override
public void doWork() {
System.out.println("firstService work");
}
}
#Service
#Qualifier("secondService")
public static class SecondServiceImpl implements MyService {
#Override
public void doWork() {
System.out.println("secondService work");
}
}
#Component
public static class FirstManager {
private final MyService myService;
#Autowired // inject FirstServiceImpl
public FirstManager(#Qualifier("firstService") MyService myService) {
this.myService = myService;
}
#PostConstruct
public void startWork() {
System.out.println("firstManager start work");
myService.doWork();
}
}
#Component
public static class SecondManager {
private final List<MyService> myServices;
#Autowired // inject MyService all implementations
public SecondManager(List<MyService> myServices) {
this.myServices = myServices;
}
#PostConstruct
public void startWork() {
System.out.println("secondManager start work");
myServices.forEach(MyService::doWork);
}
}
}
For the second part of your question, take look at this useful answers first / second
You can also make it work by giving it the name of the implementation.
Eg:
#Autowired
MyService firstService;
#Autowired
MyService secondService;
Assume that you have a GreetingService
public interface GreetingService {
void doGreetings();
}
And you have 2 implementations HelloService
#Service
#Slf4j
public class HelloService implements GreetingService{
#Override
public void doGreetings() {
log.info("Hello world!");
}
}
and HiService
#Slf4j
#Service
public class HiService implements GreetingService{
#Override
public void doGreetings() {
log.info("Hi world!");
}
}
Then you have another interface, which is BusinessService to call some business
public interface BusinessService {
void doGreetings();
}
There are some ways to do that
#1. Use #Autowired
#Component
public class BusinessServiceImpl implements BusinessService{
#Autowired
private GreetingService hiService; // Spring automatically maps the name for you, if you don't want to change it.
#Autowired
private GreetingService helloService;
#Override
public void doGreetings() {
hiService.doGreetings();
helloService.doGreetings();
}
}
In case you need to change your implementation bean name, refer to other answers, by setting the name to your bean, for example #Service("myCustomName") and applying #Qualifier("myCustomName")
#2. You can also use constructor injection
#Component
public class BusinessServiceImpl implements BusinessService {
private final GreetingService hiService;
private final GreetingService helloService;
public BusinessServiceImpl(GreetingService hiService, GreetingService helloService) {
this.hiService = hiService;
this.helloService = helloService;
}
#Override
public void doGreetings() {
hiService.doGreetings();
helloService.doGreetings();
}
}
This can be
public BusinessServiceImpl(#Qualifier("hiService") GreetingService hiService, #Qualifier("helloService") GreetingService helloService)
But I am using Spring Boot 2.6.5 and
public BusinessServiceImpl(GreetingService hiService, GreetingService helloService)
is working fine, since Spring automatically get the names for us.
#3. You can also use Map for this
#Component
#RequiredArgsConstructor
public class BusinessServiceImpl implements BusinessService {
private final Map<String, GreetingService> servicesMap; // Spring automatically get the bean name as key
#Override
public void doGreetings() {
servicesMap.get("hiService").doGreetings();
servicesMap.get("helloService").doGreetings();
}
}
List also works fine if you run all the services. But there is a case that you want to get some specific implementation, you need to define a name for it or something like that. My reference is here
For this one, I use #RequiredArgsConstructor from Lombok.
As mentioned in the comments, by using the #Qualifier annotation, you can distinguish different implementations as described in the docs.
For testing, you can use also do the same. For example:
#RunWith(SpringRunner.class)
#SpringBootTest
public class MyClassTests {
#Autowired
private MyClass testClass;
#MockBean
#Qualifier("default")
private MyImplementation defaultImpl;
#Test
public void givenMultipleImpl_whenAutowiring_thenReturnDefaultImpl() {
// your test here....
}
}
There are 2 approaches when we have autowiring of an interface with multiple implementations:
Spring #Primary annotation
In short it tells to our Spring application whenever we try to autowire our interface to use that specific implementation which is marked with the #Primary annotation. It is like a default autowiring setting. It can be used only once per cluster of implementations of an interface. → #Primary Docs
Spring #Qualifier annotation
This Spring annotation is giving us more control to select the exact implementation wherever we define a reference to our interface choosing among its options. → #Qualifier Docs
For more details follow the links to their documentation.
public interface SomeInterfaces {
void send(String message);
String getType();
}
kafka-service
#Component
public class SomeInterfacesKafkaImpl implements SomeInterfaces {
private final String type = "kafka";
#Override
public void send(String message) {
System.out.println(message + "through Kafka");
}
#Override
public String getType() {
return this.type;
}
}
redis-service
#Component
public class SomeInterfacesRedisImpl implements SomeInterfaces {
private final String type = "redis";
#Override
public void send(String message) {
System.out.println(message + "through Redis");
}
#Override
public String getType() {
return this.type;
}
}
master
#Component
public class SomeInterfacesMaster {
private final Set<SomeInterfaces> someInterfaces;
public SomeInterfacesMaster(Set<SomeInterfaces> someInterfaces) {
this.someInterfaces = someInterfaces;
}
public void sendMaster(String type){
Optional<SomeInterfaces> service =
someInterfaces
.stream()
.filter(service ->
service.getType().equals(type)
)
.findFirst();
SomeInterfaces someService =
service
.orElseThrow(() -> new RuntimeException("There is not such way for sending messages."));
someService .send(" Hello. It is a letter to ....");
}
}
test
#SpringBootTest
public class MultiImplementation {
}
#TestInstance(TestInstance.Lifecycle.PER_CLASS)
class SomeInterfacesMasterTest extends MultiImplementation {
#Autowired
private SomeInterfacesMaster someInterfacesMaster;
#Test
void sendMaster() {
someInterfacesMaster.sendMaster("kafka");
}
}
Thus, according to the Open/Closed principle, we only need to add an implementation without breaking existing code.
#Component
public class SomeInterfacesRabbitImpl implements SomeInterfaces {
private final String type = "rabbit";
#Override
public void send(String message) {
System.out.println(message + "through Rabbit");
}
#Override
public String getType() {
return this.type;
}
}
test-v2
#TestInstance(TestInstance.Lifecycle.PER_CLASS)
class SomeInterfacesMasterTestV2 extends MultiImplementation {
#Autowired
private SomeInterfacesMaster someInterfacesMaster;
#Test
void sendMasterV2() {
someInterfacesMaster.sendMaster("rabbit");
}
}
If we have multiple implementations of the same interface, Spring needs to know which one it should be autowired into a class. Here is a simple example of validator for mobile number and email address of Employee:-
Employee Class:
public class Employee {
private String mobileNumber;
private String emailAddress;
...
/** Getters & Setters omitted **/
}
Interface EmployeeValidator:
public interface EmployeeValidator {
public Employee validate(Employee employee);
}
First implementation class for Mobile Number Validator:
#Component(value="EmployeeMobileValidator")
public class EmployeeMobileValidator implements EmployeeValidator {
#Override
public Employee validate(Employee employee) {
//Mobile number Validation logic goes here.
}
}
Second implementation class for Email address Validator:
#Component(value="EmployeeEmailValidator")
public class EmployeeEmailValidator implements EmployeeValidator {
#Override
public Employee validate(Employee employee) {
//Email address validation logic goes here.
}
}
We can now autowired these above validators individually into a class.
Employee Service Interface:
public interface EmployeeService {
public void handleEmployee(Employee employee);
}
Employee Service Implementation Class
#Service
public class EmployeeServiceImpl implements EmployeeService {
/** Autowire validators individually **/
#Autowired
#Qualifier("EmployeeMobileValidator") // Autowired using qualifier for mobile validator
private EmployeeValidator mobileValidator;
#Autowired
#Qualifier("EmployeeEmailValidator") // Autowired using qualifier for email valodator
private EmployeeValidator emailValidator;
#Override
public void handleEmployee(Employee employee) {
/**You can use just one instance if you need**/
employee = mobileValidator.validate(employee);
}
}
I have my own custom Spring Data common repository in order to provide common behavior to all Spring Data repositories. And all I need is to modify EntityManager when repository is being created. But I can't inject a Spring bean into JpaRepositoryFactoryBean due to the bean is created via new operator.
public class BasicJpaRepositoryFactoryBean<T extends Repository<S, ID>, S, ID extends Serializable> extends JpaRepositoryFactoryBean<T, S, ID> {
#Autowired
private SomeService service; // - it does not work
#Override
protected RepositoryFactorySupport createRepositoryFactory(EntityManager em) {
// do some logic here
service.doSmth();
return new CommonRepositoryFactory<>(em);
}
private static class CommonRepositoryFactory<T, I extends Serializable> extends JpaRepositoryFactory {
private final EntityManager em;
public CommonRepositoryFactory(EntityManager em) {
super(em);
this.em = em;
}
#SuppressWarnings("unchecked")
protected Object getTargetRepository(RepositoryMetadata metadata) {
JpaEntityInformation entityInformation = getEntityInformation(metadata.getDomainType());
return new CommonRepositoryImpl(entityInformation, em);
}
protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {
return CommonRepositoryImpl.class;
}
}
}
Implement a setter in that class or one that extends from it.
Approach 1:
Below are the two service classes which are using same 2 repositories.
#org.springframework.stereotype.Service(value = "userService")
public class UserServiceImpl implements UserService {
#Autowired
private CounterRepository counterRepository;
#Autowired
private SessionRepository sessionRepository;
}
#org.springframework.stereotype.Service(value = "projectService")
public class UserServiceImpl implements UserService {
#Autowired
private CounterRepository counterRepository;
#Autowired
private SessionRepository sessionRepository;
}
So in above classes, as you see that CounterRepository & SessionRepository are using two times each in UserServiceImpl & ProjectServiceImpl services.
Is this is correct approach or I can make One Factory Class and use it to get required repo.
Approach 2:
class RepoFactory{
#Autowired
private CounterRepository counterRepository;
#Autowired
private SessionRepository sessionRepository;
public <T> T getRepo(Class<T> entityClass) {
if (entityClass == CounterRepository .class) {
return (T) appMessageRepository;
} else if (entityClass == SessionRepository.class) {
return (T) auditTrailRepository;
}
}
And I use like below
#org.springframework.stereotype.Service(value = "userService")
public class UserServiceImpl implements UserService {
#Autowired
private RepoFactory repoFactory;
public void someMethod(){
repoFactory.getRepo(CounterRepository.class);
.....
}
public void someMethod2(){
repoFactory.getRepo(SessionRepository.class);
.....
}
}
#org.springframework.stereotype.Service(value = "projectService")
public class ProjectServiceImpl implements ProjectService {
#Autowired
private RepoFactory repoFactory;
public void someMethod(){
repoFactory.getRepo(CounterRepository.class);
.....
}
public void someMethod2(){
repoFactory.getRepo(SessionRepository.class);
.....
}
}
Could you please help me out which approach is better according to performance and memory consumption.
If you don't configure it explictly, all spring beans are singleton, it will not affect memory at all! http://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#beans-factory-scopes
The first approach is easy to go, recommended!!
The second approach is totally unnecessary, if you want to, you can always autowire applicationContext and use applicationContext.getBean(Mybean.class)
If you have to save some memory on application start, you can have a look at #Lazy, but from my point of view, it is also not necessary.