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

【问题标题】：Spring + Powermock + JUnit call another service from one service - NullPointerExceptionSpring + Powermock + JUnit 从一个服务调用另一个服务 - NullPointerException
【发布时间】：2018-12-26 18:45:10
【问题描述】：

获取 NullPointerException。不知道我做错了什么。任何帮助将不胜感激。

调用时获取NullPointer

Teacher t = teacherService.getTeacherDetails();

我进行了调试，发现teacherService 为空。我不是为什么它为空，因为我已经在我的测试类中模拟了这个对象。

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;
    }

【问题讨论】：

既然您是在对StudentService 进行单元测试，那么您应该只将模拟注入到您的StudentService 实例中，包括TeacherService 的模拟实例
getStudentInformaition() 返回什么？ Student s?
@StalemateOfTuning 是的，已更新

标签： spring-boot junit mockito powermock

【解决方案1】：

问题在于这段代码

@InjectMocks
StudentService studentService;

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

你应该把你的代码调整成这样：

@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，并且根本不再需要 TeacherRepository

【讨论】：

我的目标是调用将调用教师服务并执行业务逻辑的学生服务。如果我只是模拟教师服务，我的目标将无法实现。
那么你没有单元测试StudentService。如果您真的非常想走这条路，那么您需要避免@InjectMocks 的魔力并手动构造StudentService 的实例
@SK。你不应该在TeacherService 类中测试teacherService 吗？
@SK。 BTW @Autowired 是 Spring 的东西，在这里没有发挥作用。 PowerMockito 将忽略该注释