Is there a way to get an instance of EntityManager injected in a custom bean validator when executing a @WebMvcTest with Spring Boot?

Question

I have created a custom bean validator as follows:

public class UniqueValidator implements ConstraintValidator<Unique, Object> {

    private final EntityManager entityManager;
    private Class<?> entityClass;
    private String entityField;

    public UniqueValidator(EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    public void initialize(Unique constraint) {
        entityClass = constraint.entityClass();
        entityField = constraint.entityField();
    }

    public boolean isValid(Object value, ConstraintValidatorContext context) {
        return !ExistsValidation.exists(entityManager, entityClass, entityField, value);
    }

}

It works nicely, but when I hit the endpoint in a test context, the EntityManager does not get injected and throws the exception: Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'javax.persistence.EntityManager' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}

That's the test I'm trying to get working:

@WebMvcTest(ProposalController.class)
class ProposalControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Autowired
    private ObjectMapper objectMapper;

    @MockBean
    private ProposalRepository proposalRepository;

    @Test
    public void testCreateProposal() throws Exception {
        // given
        var request = new ProposalRequest(
                "Tânia",
                "Bárbara Mendes",
                "159.296.683-70",
                "[email protected]",
                LocalDate.of(2000, 12, 9));
        ArgumentCaptor<Proposal> captor = ArgumentCaptor.forClass(Proposal.class);

        // when
        MockHttpServletResponse response = mockMvc.perform(
                post("/proposals").contentType(MediaType.APPLICATION_JSON)
                        .content(objectMapper.writeValueAsString(request)))
                .andReturn().getResponse();

        // then
        verify(proposalRepository, times(1)).save(captor.capture());

        assertThat(captor.getValue()).isEqualToComparingFieldByField(request.toProposal());
        assertThat(response.getStatus()).isEqualTo(CREATED.value());
    }
}

How can I get the EntityManager been injected on custom bean validator when executing the above test scenario?

Answer 1

There are multiple ways to provide the EntityManager. But I assume for this test you want to mock it to have control over its behavior.

For this to work, simply add

@MockBean
private EntityManager entityManager;

... and you'll get a mocked version of your EntityManager inside your sliced Spring Context.

For a real EntityManager you have to provide a database for your test. You can either use an in-memory database or use Testcontainers to start one using Docker.

You can then combine @WebMvcTest and @DataJpaTest on the same test and get a sliced Spring Context with all JPA and MVC related components.