Question

获取NullPointerException。不知道我在做什么错。任何帮助将不胜感激。

调用时获取NullPointer

Teacher t = teacherService.getTeacherDetails();

我确实进行了调试，并且看到TeacherService为空。我不是为什么它为null，因为我已经在测试类中模拟了此对象。

StudentServiceTest.java

@RunWith(PowerMockRunner.class)
@PrepareForTest({StudentService.class, TeacherService.class})
public class StudentServiceTest{

    @InjectMocks
    StudentService studentService;

    @InjectMocks
    TeacherService teacherService;

    @Mock
    private StudentRepository studentRepository;

    @Mock
    private TeacherRepository teacherRepository;

    @Test
    public void getStudentInformation() {
        Student student = new Student();
        Teacher teacher = new Teacher();

        when(studentRepository.getStudentDetails()).thenReturn(student);
        when(teacherRepository.getTeacherDetails()).thenReturn(teacher);

        Student student = studentService.getStudentInformaition();

    }

StudentService.java

   private TeacherService teacherService;

   @Autowired
    public StudentService(TeacherService teacherService) {
        this.teacherService = teacherService;
    }

    public Student getStudentInformaition() {
        Teacher t = teacherService.getTeacherDetails();
        // some logic
        Student s = studentRepository.getStudentDetails();
       // some more logic
       return s;
    }

TeacherService.java

 public Teacher getTeacherDetails() {
        Teacher t = teacherRepository.getTeacherDetails();
        return t;
    }

Answer 1

问题是此代码

@InjectMocks
StudentService studentService;

将已定义的模拟对象实例注入到studentService实例中，但是TeacherService的实例不是模拟对象，因此不会作为模拟对象注入到studentService实例中。

您应该将代码调整为以下形式：

@RunWith(PowerMockRunner.class)
@PrepareForTest({StudentService.class, TeacherService.class})
public class StudentServiceTest{

    @InjectMocks
    StudentService studentService;

    @Mock
    TeacherService teacherService;

    @Mock
    private StudentRepository studentRepository;

    @Test
    public void getStudentInformation() {
        Student student = new Student();
        Teacher teacher = mock(Teacher.class);

        when(studentRepository.getStudentDetails()).thenReturn(student);
        when(teacherService.getTeacherDetails()).thenReturn(teacher);
        when(teacher.getFoo()).thenReturn(???);

        Student student = studentService.getStudentInformaition();

    }

请注意，teacherService现在是一个模拟对象实例，TeacherRepository完全不再需要

Spring + Powermock + JUnit从一个服务调用另一个服务-NullPointerException

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