在 SpringBoot API 中测试时 controller 上出现 NullPointerException - Mocking

Question

I don't know why, but my code is giving me a nullPointerException error when I try to use test any of my methods from the controller using MVC. Here I put some parts of code:

My controller (first method only):

@RestController
@RequestMapping(path = "/companias")
public class ControllerAPI {


    @Autowired
    private final CompaniaServiceImpl companiaService;

    public ControllerAPI(CompaniaServiceImpl companiaService) {
        this.companiaService = companiaService;
    }

    @ResponseStatus(HttpStatus.OK)
    @GetMapping("/{companiaId}/{field_name}")
    public Map<String, List<Object>> getByField(
        @PathVariable("companiaId") Long companiaId,
        @PathVariable("field_name") String fieldName) {

        return companiaService.getCompaniaByfield(companiaId, fieldName);

    }

Here is my Service (the one I'm trying to mock):

@Service
@Slf4j
public class CompaniaServiceImpl implements CompaniaService {


    private final CompaniaRepository companiaRepository;
    private final DefaultGroupRepository defaultGroupRepository;
    private final OfficeRepository officeRepository;

    @Autowired
    public CompaniaServiceImpl(CompaniaRepository companiaRepository, DefaultGroupRepository defaultGroupRepository, OfficeRepository officeRepository) {
        this.companiaRepository = companiaRepository;
        this.defaultGroupRepository = defaultGroupRepository;
        this.officeRepository = officeRepository;
    }


    public Map<String, List<Object>> getCompaniaByfield(Long companiaId, String fieldName) {

        if (companiaRepository.existsById(companiaId)) {
            Map<String, Function<Compania, Object>> mapCompania = Map.of(
                "name", Compania::getName,
                "dominio", Compania::getDominio,
                "altas", Compania::getAltas,
                "bajas", Compania::getBajas
            );

            Compania c = companiaRepository.findCompaniaById(companiaId);
            Function<Compania, Object> retriever = mapCompania.get(fieldName);


            return Collections.singletonMap("success", List.of(retriever.apply(c)));
        }
        else throw new IllegalStateException(
            "Compania con id (" + companiaId + ") no existe"
        );

    }

Here is my controller Test :

@ExtendWith(SpringExtension.class)
@ContextConfiguration
class ControllerAPITest {

    String token = "xxx";

    @InjectMocks
    private ControllerAPI controllerAPI;

    private CompaniaServiceImpl companiaService = Mockito.mock(CompaniaServiceImpl.class);

    private MockMvc mockMvc;

    @Before
    public void setup() throws Exception{

        MockitoAnnotations.initMocks(this);

        this.mockMvc = MockMvcBuilders.standaloneSetup(controllerAPI).build();
    }


    @Test
    void getByField() throws Exception {
        Map<String, List<Object>> response = Collections.singletonMap("success", List.of("nombre1"));
        Mockito.when(companiaService.getCompaniaByfield(1L,"name")).thenReturn(response);

        this.mockMvc.perform(
                get("/companias/{companiaId}/{field_name}", 1L, "name")
                    .header("authorization", "Bearer " + token)
                    .contentType(MediaType.APPLICATION_JSON))
            .andDo(print())
            .andExpect(status().isOk())
            .andExpect(jsonPath("$.success[0]").isNotEmpty())
            .andExpect(jsonPath("$.success[0]").value("nombre1"));
    }

And the NullPointerException error that is giving me:

java.lang.NullPointerException
    at database.configuration.controller.ControllerAPITest.getByField(ControllerAPITest.java:69)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:686)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:212)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:208)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:137)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:71)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:248)
    at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$5(DefaultLauncher.java:211)
    at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:226)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:199)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:132)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)

It gives me this error in the line that says this.mockMvc.perform( I don't know why I'm not being able to mock my service. If you could help me, I'd really appreciate it

Answer 1

The main issue in your test is that you are mixing JUnit 4 annotations and JUnit5 in a single test. The @Before is from JUnit4 so the setup is never being run, hence no dependencies or mocks will be created. Hence a NullPointerException as nothing is injected.

In your code you should use the CompaniaService interface instead of the CompaniaServiceImpl . You have defined an interface which you should use to your advantage.

Change your controller.

@RestController
@RequestMapping(path = "/companias")
public class ControllerAPI {


    private final CompaniaService companiaService;

    public ControllerAPI(CompaniaService companiaService) {
        this.companiaService = companiaService;
    }

You don't need the @Autowired on the field as injection is done through the constructor..

Now for your test you can do a couple of things.

1. Replace @Before with @BeforeEach which is the JUnit5 annotation to mark the method. You don't need the @ExtendsWith and @ContextConfiguration .

2. Instead of the @ExtendsWith(SpringExtension.class) use the MockitoExtension , use @BeforeEach but not to initialize the mocks.

3. Use @WebMvcTest and @MockBean and let Spring Boot handle the injection and mock creation for you.

Use proper annotations

class ControllerAPITest {

    String token = "xxx";

    @InjectMocks
    private ControllerAPI controllerAPI;

    @Mock
    private CompaniaService companiaService;

    private MockMvc mockMvc;

    @BeforeEach
    public void setup() throws Exception{

        MockitoAnnotations.initMocks(this);

        this.mockMvc = MockMvcBuilders.standaloneSetup(controllerAPI).build();
    }


   @Test
   void getByField() throws Exception {  ... }

Use MockitoExtension

@ExtendsWith(MockitoExtension.class)
class ControllerAPITest {

    String token = "xxx";

    @InjectMocks
    private ControllerAPI controllerAPI;

    @Mock
    private CompaniaService companiaService;

    private MockMvc mockMvc;

    @BeforeEach
    public void setup() throws Exception{
        this.mockMvc = MockMvcBuilders.standaloneSetup(controllerAPI).build();
    }

   @Test
   void getByField() throws Exception {  ... }

Use @WebMvcTest

@WebMvcTest(ControllerAPI.class)
class ControllerAPITest {

    String token = "xxx";

    @MockBean
    private CompaniaService companiaService;

    @Autowired
    private MockMvc mockMvc;


   @Test
   void getByField() throws Exception {  ... }