[FIXED] ModelMapper JUnit Mockito throwing "com.where.where.mapper.ModelMapperService.forRequest()" is null

Issue

I'm trying to test a method in service class which uses ModelMapper to convert dto to entity, but I'm getting NullPointerException at this line. how do i fix it?

Exception

java.lang.NullPointerException: Cannot invoke "org.modelmapper.ModelMapper.map(Object, java.lang.Class)" because the return value of "com.where.where.mapper.ModelMapperService.forRequest()" is null

at com.where.where.service.ScoreServiceTest.whenCreateScoreCalledWithValidRequest_itShouldReturnValidCreateScoreRequest(ScoreServiceTest.java:44)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:725)
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$7(TestMethodTestDescriptor.java:214)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:210)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:66)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:151)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
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)

Test Class

public class ScoreServiceTest {

    private ScoreRepository scoreRepository;
    private ScoreService scoreService;
    private ModelMapperService modelMapperService;


    @BeforeEach
    void setUp() {
        scoreRepository = mock(ScoreRepository.class);
        modelMapperService = mock(ModelMapperService.class);
        scoreService = new ScoreService(scoreRepository,modelMapperService);
    }

    @Test
    void whenCreateScoreCalledWithValidRequest_itShouldReturnValidCreateScoreRequest() {
        CreateScoreRequest createScoreRequest = new CreateScoreRequest();
        createScoreRequest.setVenueScore(3);
        createScoreRequest.setCoronaScore(2);
        createScoreRequest.setCreateDate("17-3-2022");
        createScoreRequest.setPlaceId(1L);
        createScoreRequest.setUserId(1L);

        Score score = new Score();
        score.setId(1L);
        score.setCoronaScore(2);
        score.setVenueScore(3);
        score.setCreateDate("17-3-2022");
        
        when(modelMapperService.forRequest().map(org.mockito.ArgumentMatchers.any(), org.mockito.ArgumentMatchers.any())).thenReturn(score);
        when(score.getId()).thenReturn(1L);
        when(scoreRepository.save(ArgumentMatchers.any(Score.class))).thenReturn(score);

        Score result = scoreRepository.save(score);

        assertEquals(result,score);
    }
}

Score Service

@Service
@RequiredArgsConstructor
public class ScoreService {
    private final ScoreRepository scoreRepository;
    private final ModelMapperService modelMapperService;

    public CreateScoreRequest add(CreateScoreRequest createScoreRequest) {
        Score score = modelMapperService.forRequest().map(createScoreRequest, Score.class);
        scoreRepository.save(score);
        return createScoreRequest;
    }

    public List<ScoreDto> getAll() {
        List<Score> result = scoreRepository.findAll();
        List<ScoreDto> response = result.stream().map(score -> modelMapperService.forDto().map(score, ScoreDto.class))
                .collect(Collectors.toList());
        return response;
    }

    public ScoreDto getById(Long id) {
        Score score = scoreRepository.getById(id);
        ScoreDto response = modelMapperService.forDto().map(score, ScoreDto.class);
        return response;
    }

    public void delete(Long id) {
        scoreRepository.deleteById(id);
    }

    public CreateScoreRequest update(Long id, CreateScoreRequest updateScoreDto) {
        if (scoreRepository.existsById(id)) {
            Score score = modelMapperService.forRequest().map(updateScoreDto, Score.class);
            score.setId(id);
            scoreRepository.save(score);
            return updateScoreDto;
        }
        throw new ScoreNotFoundException("Score does not found.");

    }
}

Mapper I am using this class.

import org.modelmapper.ModelMapper;
import org.modelmapper.convention.MatchingStrategies;

@Service
@RequiredArgsConstructor
public class ModelMapperManager implements ModelMapperService {
    private final ModelMapper modelMapper;

    @Override
    public ModelMapper forDto() {
        this.modelMapper.getConfiguration().setAmbiguityIgnored(true).setMatchingStrategy(MatchingStrategies.LOOSE);
        return modelMapper;
    }

    @Override
    public ModelMapper forRequest() {
        this.modelMapper.getConfiguration().setAmbiguityIgnored(true).setMatchingStrategy(MatchingStrategies.STANDARD);
        return modelMapper;
    }
}

Solution

You need one more mock, for modelMapperService.forRequest() to return.

So you might have

modelMapper = mock(ModelMapper.class);

and then you'll be able to write

when(modelMapperService.forRequest()).thenReturn(modelMapper);
when(modelMapper.map(ArgumentMatchers.any(), ArgumentMatchers.any())).thenReturn(score);

instead of trying to do the two steps all on one line.

Answered By - Dawood ibn Kareem
Answer Checked By - Mildred Charles (JavaFixing Admin)