How to: Spring get rid of @Validate for automatic Controller validation?

Question

I know about @Valid annotation to instruct spring to validate for example a Controller argument according to JSR-303 in such this example:

@GetMapping("/test")
public TestDTO testDTO(@Valid TestDTO testDTO){
        return testDTO;
}

But I would like to be able to configure Spring in some way to enable validation in all my controllers without specify explicitly the @Valid annotation.

Is that possible in any way? Some Spring configuration? Making use of AOP?...

Answer 1

I have finally came across with a working solution which may be not the optimal from the point of view of Spring configuration (as I said I'm Spring beginner).

The idea was to modify the argument resolvers (the ones that implement HandlerMethodArgumentResolver), replacing the argument resolver associated to arguments with a @RequestBody annotation. Creating an inherited class from the default one (which is RequestResponseBodyMethodProcessor) and overriding a method in the class hierarchy which efectively determines if perform a validation or not (based in the presence of @Valid, @Validated, @ValidXxxxxx annotations as the default behaviour), making to always validate with no further check.

So here is the code (I'm using Java 8 BTW):

Extend RequestResponseBodyMethodProcessor to define validation strategy (in this case, always validate):

public class MyRequestResponseBodyMethodProcessor extends RequestResponseBodyMethodProcessor {

    public MyRequestResponseBodyMethodProcessor(List<HttpMessageConverter<?>> converters) {
        super(converters);
    }

    @Override
    protected void validateIfApplicable(WebDataBinder binder, MethodParameter parameter) {
        binder.validate();      // always validating @RequestMapping annotated parameters ;)
    }
}

Define a @Configuration class where to replace default argument resolver:

@Configuration
public class MyValidationAdapterConfigurer {

    @Autowired
    private RequestMappingHandlerAdapter requestMappingHandlerAdapter;

    // Injecting your own resolver
    @Autowired
    private RequestResponseBodyMethodProcessor requestResponseBodyMethodProcessor;


    @PostConstruct
    public void init() {

        // Don't know why but, removing the target resolver and adding the injected one to the end does not work!
        // Must be something related with the resolvers ordering. So just replacing the target in the same position.
        final List<HandlerMethodArgumentResolver> mangledResolvers = requestMappingHandlerAdapter.getArgumentResolvers().stream()
            .map(resolver -> resolver.getClass().equals(RequestResponseBodyMethodProcessor.class) ?
                requestResponseBodyMethodProcessor: resolver)
            .collect(Collectors.toList());

        requestMappingHandlerAdapter.setArgumentResolvers(mangledResolvers);
    }

}

Finally configure Spring to deliver your customized Bean in your Application configuration class:

@Configuration
@PropertySource("classpath:api.properties")
public class MyRestApiConfiguration {

    @Bean
    @Autowired
    RequestResponseBodyMethodProcessor requestResponseBodyMethodProcessor(List<HttpMessageConverter<?>> converters) {
        return new MyRequestResponseBodyMethodProcessor(converters);
    }

}

Answer 2

unfortunately there is no "legal" way to do it.

Furthermore @Valid is not enough. You need also a BindingResult method parameter to be able to check the validation result: bindingResult.hasErrors()

If you don't want to use BindingResult, you could write your own Validator and throw an Exception in case of invalid input.