Testing Spring @MVC annotations

Question

I ran into a problem the other day where a @Valid annotation was accidentally removed from a controller class. Unfortunately, it didn't break any of our tests. None of our unit tests actually exercise the Spring AnnotationMethodHandlerAdapter pathway. We just test our controller classes directly.

How can I write a unit or integration test that will correctly fail if my @MVC annotations are wrong? Is there a way I can ask Spring to find and exercise the relevant controller with a MockHttpServlet or something?

Answer 1

Sure. There's no reason why your test can't instantiate its own DispatcherServlet, inject it with the various items which it would have in a container (e.g. ServletContext), including the location of the context definition file.

Spring comes with a variety of servlet-related MockXYZ classes for this purpose, including MockServletContext, MockHttpServletRequest and MockHttpServletResponse. They're not really "mock" objects in the usual sense, they're more like dumb stubs, but they do the job.

The servlet's test context would have the usual MVC-related beans, plus your beans to test. Once the servlet is initialized, create the mock requests and responses, and feed them into the servet's service() method. If request gets routed correctly, you can check the results as written to the mock response.

Answer 2

How about a code example :)

Answer 3

I write integration tests for this kind of thing. Say you have a bean with validation annotations:

public class MyForm {
    @NotNull
    private Long myNumber;

    ...
}

and a controller that handles the submission

@Controller
@RequestMapping("/simple-form")
public class MyController {
    private final static String FORM_VIEW = null;

    @RequestMapping(method = RequestMethod.POST)
    public String processFormSubmission(@Valid MyForm myForm,
            BindingResult result) {
        if (result.hasErrors()) {
            return FORM_VIEW;
        }
        // process the form
        return "success-view";
    }
}

and you want to test that the @Valid and @NotNull annotations are wired correctly:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"file:web/WEB-INF/application-context.xml",
    "file:web/WEB-INF/dispatcher-servlet.xml"})
public class MyControllerIntegrationTest {

    @Inject
    private ApplicationContext applicationContext;

    private MockHttpServletRequest request;
    private MockHttpServletResponse response;
    private HandlerAdapter handlerAdapter;

    @Before
    public void setUp() throws Exception {
        this.request = new MockHttpServletRequest();
        this.response = new MockHttpServletResponse();

        this.handlerAdapter = applicationContext.getBean(HandlerAdapter.class);
    }

    ModelAndView handle(HttpServletRequest request, HttpServletResponse response)
            throws Exception {
        final HandlerMapping handlerMapping = applicationContext.getBean(HandlerMapping.class);
        final HandlerExecutionChain handler = handlerMapping.getHandler(request);
        assertNotNull("No handler found for request, check you request mapping", handler);

        final Object controller = handler.getHandler();
        // if you want to override any injected attributes do it here

        final HandlerInterceptor[] interceptors =
            handlerMapping.getHandler(request).getInterceptors();
        for (HandlerInterceptor interceptor : interceptors) {
            final boolean carryOn = interceptor.preHandle(request, response, controller);
            if (!carryOn) {
                return null;
            }
        }

        final ModelAndView mav = handlerAdapter.handle(request, response, controller);
        return mav;
    }

    @Test
    public void testProcessFormSubmission() throws Exception {
        request.setMethod("POST");
        request.setRequestURI("/simple-form");
        request.setParameter("myNumber", "");

        final ModelAndView mav = handle(request, response);
        // test we're returned back to the form
        assertViewName(mav, "simple-form");
        // make assertions on the errors
        final BindingResult errors = assertAndReturnModelAttributeOfType(mav, 
                "org.springframework.validation.BindingResult.myForm", 
                BindingResult.class);
        assertEquals(1, errors.getErrorCount());
        assertEquals("", errors.getFieldValue("myNumber"));        
    }

See my blog post on integration testing Spring's MVC annotations