Java – Custom spring annotations for request parameters

I want to write a custom annotation that will modify the spring request or path parameters according to the annotation For example, instead of this Code:

@RequestMapping(method = RequestMethod.GET)
public String test(@RequestParam("title") String text) {
   text = text.toUpperCase();
   System.out.println(text);
   return "form";
}

I can comment @ uppercase:

@RequestMapping(method = RequestMethod.GET)
   public String test(@RequestParam("title") @UpperCase String text) {
   System.out.println(text);
   return "form";
}

Is it possible? If so, what should I do?

Solution

As people say in comments, you can easily write your annotation - driven custom parser Four simple steps,

>Create a comment, for example

@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface UpperCase {
    String value();
}

>Write a parser, for example

public class UpperCaseResolver implements HandlerMethodArgumentResolver {

    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.getParameterAnnotation(UpperCase.class) != null;
    }

    public Object resolveArgument(MethodParameter parameter,ModelAndViewContainer mavContainer,NativeWebRequest webRequest,WebDataBinderFactory binderFactory) throws Exception {
        UpperCase attr = parameter.getParameterAnnotation(UpperCase.class);
        return webRequest.getParameter(attr.value()).toUpperCase();
    }
}

>Register parser

<mvc:annotation-driven>
        <mvc:argument-resolvers>
            <bean class="your.package.UpperCaseResolver"></bean>
        </mvc:argument-resolvers>
</mvc:annotation-driven>

Or Java configuration

@Configuration
    @EnableWebMvc
    public class Config extends WebMvcConfigurerAdapter {
    ...
      @Override
      public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
          argumentResolvers.add(new UpperCaseResolver());
      }
    ...
    }

>Use annotations in controller methods, such as

public String test(@UpperCase("foo") String foo)