请求参数的自定义Spring注释

Question

我想编写自定义注释,根据注释修改Spring请求或路径参数.例如,而不是这段代码:

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

我可以制作注释@UpperCase:

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

它是否可能,如果是,我怎么能这样做？

Answer 1

正如这些人在评论中所说,你可以轻松编写注释驱动的自定义解析器.四个简单的步骤,

1. 创建一个注释,例如

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

2. 写一个解析器,例如

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. 注册一个解析器

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

或者是java配置

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

4. 在控制器方法中使用注释,例如

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