自定义HandlerMethodArgumentResolver

前言

今天在做一个后台的管理列表，猛然发现有8~9个查询参数，心里一想：又 TMD 要想一坨子 @RequestParam了。突然就想：妈的不想这样了。想着用一个对象来封装这些查询参数。但我们公司是有要求 前端给的参数都是以下划线，而后端用的都是驼峰命名。如何转换成了问题。以下是在请教大佬之后，大佬给的方案，感谢大佬，特记下学习一下。

代码

@Target({ElementType.PARAMETER, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface PropertyNaming {

}

public class PropertyNamingStrategyArgumentResolver implements HandlerMethodArgumentResolver {

    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.hasParameterAnnotation(PropertyNaming.class);
    }

    @Override
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
        String name = ModelFactory.getNameForParameter(parameter);
        Object attribute = (mavContainer.containsAttribute(name) ? mavContainer.getModel().get(name) :
                createAttribute(parameter));

        WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
        if (binder.getTarget() != null) {
            if (!mavContainer.isBindingDisabled(name)) {
                bindRequestParameters(binder, webRequest);
            }
            validateIfApplicable(binder, parameter);
            if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
                throw new BindException(binder.getBindingResult());
            }
        }

        // Add resolved attribute and BindingResult at the end of the model
        Map<String, Object> bindingResultModel = binder.getBindingResult().getModel();
        mavContainer.removeAttributes(bindingResultModel);
        mavContainer.addAllAttributes(bindingResultModel);

        return binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter);
    }

    /**
     * Whether to raise a fatal bind exception on validation errors.
     * @param binder the data binder used to perform data binding
     * @param methodParam the method argument
     * @return {@code true} if the next method argument is not of type {@link Errors}
     */
    protected boolean isBindExceptionRequired(WebDataBinder binder, MethodParameter methodParam) {
        int i = methodParam.getParameterIndex();
        Class<?>[] paramTypes = methodParam.getMethod().getParameterTypes();
        boolean hasBindingResult = (paramTypes.length > (i + 1) && Errors.class.isAssignableFrom(paramTypes[i + 1]));
        return !hasBindingResult;
    }

    protected void validateIfApplicable(WebDataBinder binder, MethodParameter methodParam) {
        Annotation[] annotations = methodParam.getParameterAnnotations();
        for (Annotation ann : annotations) {
            Validated validatedAnn = AnnotationUtils.getAnnotation(ann, Validated.class);
            if (validatedAnn != null || ann.annotationType().getSimpleName().startsWith("Valid")) {
                Object hints = (validatedAnn != null ? validatedAnn.value() : AnnotationUtils.getValue(ann));
                Object[] validationHints = (hints instanceof Object[] ? (Object[]) hints : new Object[] {hints});
                binder.validate(validationHints);
                break;
            }
        }
    }

    protected void bindRequestParameters(WebDataBinder binder, NativeWebRequest request) {
        Map<String, String[]> result = new HashMap<>();
        Map<String, String[]> parameterMap = request.getParameterMap();
        if(!parameterMap.isEmpty()) {
            Set<String> keys = parameterMap.keySet();
            for (String key : keys) {
                result.put(key, parameterMap.get(key));
                String translate = SnakeCaseStrategy.translate(key);
                if(translate.equals(key)){
                    continue;
                }
                result.put(translate, parameterMap.get(key));
            }
        }
        MutablePropertyValues mpvs = new MutablePropertyValues(result);
        binder.bind(mpvs);
    }

    protected Object createAttribute(MethodParameter methodParam) throws Exception {

        return BeanUtils.instantiateClass(methodParam.getParameterType());
    }

    public static class SnakeCaseStrategy {

        public static String translate(String input)
        {
            // garbage in, garbage out
            if (input == null) return input;
            int length = input.length();
            StringBuilder result = new StringBuilder(length * 2);
            boolean wasPrevTranslated = false;
            for (int i = 0; i < length; i++)
            {
                // skip first starting underscore
                char c = input.charAt(i);
                if (i > 0 && c == '_')
                {
                    wasPrevTranslated = true;
                } else if (Character.isLowerCase(c) && wasPrevTranslated) {
                    result.append(Character.toUpperCase(c));
                    wasPrevTranslated = false;
                } else {
                    result.append(c);
                }
            }
            return result.toString();
        }
    }
}

@Configuration
public class WebConfiguration extends WebMvcConfigurationSupport {

    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        argumentResolvers.add(new PropertyNamingStrategyArgumentResolver());
    }

使用

@RestController
@RequestMapping("/test")
public class TestController {

    @GetMapping
    public String test(@PropertyNaming Test test){
        return test.userName;
    }
}