java - 单元测试期间 POJO 对象上的 NullPointer

Question

这个问题已经有答案了:

What is a NullPointerException, and how do I fix it? (12 个回答)

已关闭 7 年前。

我想测试我的 Controller ，但我很难模拟对象。我有这样的非常简单的方法。

@RequestMapping(value = "/places", method = RequestMethod.GET)
public String showPlacesByQuery(Model model, @RequestParam(value = "q", required = false) String query) {

    Location location = geolocationParser.getCoords(query); //this line cause NPE
    List placesList = placeService.findPublicPlaces(location, 0);

    model.addAttribute("query", query);
    model.addAttribute("placesList", placesList);
    return "places/list";
}

我写了测试，得到 NullPointerException 。我认为原因是geolocationParser.getCoordS(query)返回null ？或者整个作业有问题 Location location = geolocationParser.getCoords(query);

@Mock
GeolocationParser geolocationParser;

@Mock
PlaceService placeService;

@Before
public void setUp() throws Exception {
    MockitoAnnotations.initMocks(this);
}

@Test
public void testShowPlacesByQuery() throws Exception {

    String query = "SomeQuery";
    PlaceController placeController = new PlaceController();

    Location location = mock(Location.class);
    location.setCity("someString");
    location.setLatitude("54.2323");
    location.setLongitude("18.2323");

    when(geolocationParser.getCoords(Mockito.anyString())).thenReturn(location);

    List<Place> expectedPlaces = asList(new Place(), new Place());
    when(placeService.findPublicPlaces(location, 0)).thenReturn(expectedPlaces);

    MockMvc mockMvc = MockMvcBuilders.standaloneSetup(placeController).build();
    mockMvc.perform(get("/places").param("q", query))
            .andDo(print())
            .andExpect(status().isOk())
            .andExpect(view().name("places/list"));
}

我花了几个小时以不同的方式让它发挥作用，但没有结果。

Answer 1

如果您正在测试 PlaceController 类，则不应手动为该类创建实例。使用@InjectMocks。

@Mock
private FormServiceImpl formService;

@Mock 
private FormDao formDao;

@InjectMocks
private PlaceController placeController;

并从此处将其删除

@Test
public void testShowPlacesByQuery() throws Exception {

    String query = "SomeQuery";
    //PlaceController placeController = new PlaceController();