Spring REST API：404与415自定义JSON响应在Postman可见但MockMVC测试无法获取的问题

Let's break down why you're seeing this discrepancy between MockMVC and TestRestTemplate, and how to fix it.

The Root Cause for 404 (NoHandlerFoundException) #

When you use MockMVC, it doesn't automatically respect the spring.mvc.throw-exception-if-no-handler-found=true property you set in application.properties. By default, MockMVC's underlying DispatcherServlet doesn't throw NoHandlerFoundException when no request handler matches — it just returns a 404 status directly, skipping your @ControllerAdvice exception handler entirely.

That’s why your status code assertion passes, but the JSON content is missing: MockMVC isn’t triggering your custom error response logic for the 404 case.

Fix for 404 Testing with MockMVC #

You need to explicitly configure MockMVC to enable the throwExceptionIfNoHandlerFound behavior in its DispatcherServlet. Here are two straightforward ways to do this:

Option 1: Customize MockMVC During Setup #

When initializing MockMVC in your test class, use webAppContextSetup and add a dispatcher servlet customizer:

@Autowired
private WebApplicationContext webApplicationContext;

private MockMvc mockMvc;

@BeforeEach
void setUp() {
    mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext)
            .addDispatcherServletCustomizer(dispatcherServlet -> 
                dispatcherServlet.setThrowExceptionIfNoHandlerFound(true))
            .build();
}

Option 2: Use a Test Configuration Bean #

If you’re using @AutoConfigureMockMvc, create a test-specific configuration bean to set this behavior globally:

@TestConfiguration
public class MockMvcCustomConfig {
    @Bean
    public DispatcherServletCustomizer dispatcherServletCustomizer() {
        return servlet -> servlet.setThrowExceptionIfNoHandlerFound(true);
    }
}

Then import this config into your test class:

@SpringBootTest
@AutoConfigureMockMvc
@Import(MockMvcCustomConfig.class)
public class YourControllerTests {
    // Your test methods here
}

Checking the 415 (UnsupportedMediaTypeStatusException) Case #

For the 415 error, ensure your MockMVC test actually sends a request with an unsupported media type to trigger the exception. For example, if your endpoint expects application/json, send a request with text/plain:

@Test
@Order(2)
public void unsupportedMediaTypeTest() throws Exception {
    mockMvc.perform(post("/user/login")
                    .contentType(MediaType.TEXT_PLAIN)
                    .content("invalid content"))
            .andExpect(status().isUnsupportedMediaType())
            .andExpect(jsonPath("$.message", is("Wrong request media type.")));
}

If you weren’t specifying an incorrect media type before, MockMVC wouldn’t hit your custom exception handler, leading to the same missing JSON issue.

Verify the Fix #

After applying the DispatcherServlet customizer for 404, your original test should work as expected:

@Test
@Order(1)
public void endpointNotFound() throws Exception {
    mockMvc.perform(post("/user/logi"))
            .andExpect(status().isNotFound())
            .andExpect(jsonPath("$.message", is("Endpoint not found.")));
}

This ensures MockMVC behaves consistently with your running application, triggering your @ControllerAdvice handlers just like TestRestTemplate does.

内容的提问来源于stack exchange，提问作者Kovo