Custom Spring annotation for request parameters

Question

I would like to write custom annotations, that would modify Spring request or path parameters according to annotations. 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 could make annotation @UpperCase :

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

Is it possible and if it is, how could I do it ?

Answer 1

As the guys said in the comments, you can easily write your annotation driven custom resolver. Four easy steps,

1. Create an annotation e.g.

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

2. Write a resolver e.g.

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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();     } } 

3. register a resolver

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

or the java config

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

4. use an annotation in your controller method e.g.

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