问使用JUnit 5+方法的Spring 5返回null

EN

@ContextConfiguration(classes = {WebAppInitializer.class, AppConfig.class, WebConfig.class})
@Transactional
@WebAppConfiguration
public class TestMainController {

    @InjectMocks
    private MainController mainController;

    private MockMvc mockMvc;

    @BeforeEach
    public void init() {
        mockMvc = MockMvcBuilders.standaloneSetup(this.mainController).build();
    }

    @Test
    public void testLoadData() throws Exception {
        MvcResult mvcResult = mockMvc
                .perform(MockMvcRequestBuilders.get("/loadData.ajax"))
                .andExpect(MockMvcResultMatchers.status().isOk()).andReturn();

        Assertions.assertNotNull(mvcResult.getResponse().getContentAsString(), "response should not be null");
    }

}

Spring version: 5.0.3
JUnit version: 5.0.3
mockito version: 1.9.5
hamcrest version: 1.3
json-path-assert version: 2.2.0

@RequestMapping(value = "/loadData.ajax", method = RequestMethod.GET)
public String loadData(HttpServletRequest request, HttpServletResponse response) {
    List list = mainService.loadData(); // starts a transaction and invokes the loadData method of mainDAO repository which basically loads data from the database
    return JSONArray.fromObject(list).toString();
}