How to validate Data in Service Layer? - spring-boot

Question

I've got a problem which I haven't been able to solve.
I am currently building a Rest Api with Spring Boot and I want to validate my User Entity inside of the service layer. I have tried different approaches, but nothing worked out for now. In my Test no Exception gets thrown when it gets to the create method.
Here is my current code:
User Entity
#Entity
#Getter
#Setter
#NoArgsConstructor
#AllArgsConstructor
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#NotBlank
#Email(message = "User needs a valid Mail.")
#Column(unique = true, nullable = false)
private String mail;
#NotBlank
#Column(nullable = false)
private String lastName;
#NotBlank
#Column(nullable = false)
private String firstName;
}
User Service
#Service
#RequiredArgsConstructor
public class UserService implements IUserService {
private final UserRepository userRepository;
#Override
public User create(#Valid User user) {
user.setId(null);
User createdUser = userRepository.save(user);
return createdUser;
}
My Test
#SpringBootTest
class UserServiceTest {
#Mock
UserRepository userRepository;
#InjectMocks
UserService userService;
#Test
void createUserFailsBecauseNoFirstName() {
User testUser = new User("test#mail.de", "LastName", "FirstName");
when(userRepository.save(any(User.class))).thenReturn(testUser);
testUser.setFirstName(null);
Assertions.assertThrows(ConstraintViolationException.class,
() -> userService.create(testUser));
}
pom.xml
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.2</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.rest</groupId>
<artifactId>test</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</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.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.9</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
</build>
</project>
What I tried:
#Validated for the Service Class (tutorial I followed)
#Validated additionally at Method Level
removing #Validated & #Validate and use Validator instead, but it doesn't get injected (followed that tutorial)

Answer 1

Because you are using #InjectMocks to get the UserService , it is not a bean that is managed by Spring since #InjectMocks is a Mockito annotation and know nothing about Spring and does not know how to get a bean from Spring container. So you are actually testing a non-spring UserService bean now and hence the validation does not takes place.
Change to use #Autowired to get the UserService bean from Spring container , and use #MockBean to replace the UserRepository bean in the Spring container with a mocked version. Also you need to add #Validated on the UserService too :
#Service
#Validated
public class UserService implements IUserService {
}
#SpringBootTest
class UserServiceTest {
#MockBean
UserRepository userRepository;
#Autowired
UserService userService;
#Test
void createUserFailsBecauseNoFirstName() {
User testUser = new User("test#mail.de", "LastName", "FirstName");
when(userRepository.save(any(User.class))).thenReturn(testUser);
testUser.setFirstName(null);
Assertions.assertThrows(ConstraintViolationException.class,
() -> userService.create(testUser));
}
}

Answer 2

Not really the solution that I was searching for, but I couldn't get it to work with Annotations even in a new Spring Boot Project. So I now used a Validator in my Service and let it validate my User.
Service
#Service
#RequiredArgsConstructor
public class UserService implements IUserService {
private final Validator validator;
private final UserRepository userRepository;
#Override
public User create(User user) {
user.setId(null);
// new Validation
Set<ConstraintViolation<T>> violations = validator.validate(objectToValidate);
if (!violations.isEmpty()) {
StringBuilder sb = new StringBuilder();
for (ConstraintViolation<T> constraintViolation : violations) {
sb.append(constraintViolation.getMessage());
}
throw new ResourceValidationException("Error occurred: " + sb.toString());
}
User createdUser = userRepository.save(user);
return createdUser;
}
Test
#SpringBootTest
class UserServiceTest {
#Mock
UserRepository userRepository;
#Autowired
Validator validator;
UserService userService = new UserService(validator, userRepository);
#Test
void createUserFailsBecauseNoFirstName() {
User testUser = new User("test#mail.de", "LastName", "FirstName");
when(userRepository.save(any(User.class))).thenReturn(testUser);
testUser.setFirstName(null);
Assertions.assertThrows(ConstraintViolationException.class,
() -> userService.create(testUser));
}
And since I always got a validator bean which didn't validate (so my tests didn't throw the expected error) and I didn't want to create a ValidatorFactory I also added a Configuration which holds a ValidatorBean.
Config
#Configuration
public class AppConfig {
#Bean
public Validator defaultValidator() {
return new LocalValidatorFactoryBean();
}
}