HandlerMethodArgumentResolver數據綁定無效

  因項目中action參數過多，而且是一些通用的查詢參數，因此準備進行對參數統一封裝爲Map對象，而後由action中傳入service中進行處理，查詢spring的資料發現能夠經過實現HandlerMethodArgumentResolver進行數參數的綁定，參考文章《擴展SpringMVC以支持更精準的數據綁定1》進行配置後。

  項目調試中發現斷點不能正常進行解析器，跟蹤源代碼找到在org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.getArgumentResolver()方法中會獲取全部已經加載的解析器，會順序執行，而我使用的Map對象會被spring自帶的解析器給處理掉，因此自定義的解析器沒法進入，HandlerMethodArgumentResolverComposite關鍵代碼：

    private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
        HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
        if (result == null) {
            for (HandlerMethodArgumentResolver methodArgumentResolver : this.argumentResolvers) {
                if (logger.isTraceEnabled()) {
                    logger.trace("Testing if argument resolver [" + methodArgumentResolver + "] supports [" +
                            parameter.getGenericParameterType() + "]");
                }
                if (methodArgumentResolver.supportsParameter(parameter)) {
                    result = methodArgumentResolver;
                    this.argumentResolverCache.put(parameter, result);
                    break;
                }
            }
        }
        return result;
    }

其中this.argumentResolvers爲LinkedList變量，元素內容：

[org.springframework.web.method.annotation.RequestParamMethodArgumentResolver@9dc12fc,
org.springframework.web.method.annotation.RequestParamMapMethodArgumentResolver@23c893fc,
org.springframework.web.servlet.mvc.method.annotation.PathVariableMethodArgumentResolver@456b97be,
org.springframework.web.servlet.mvc.method.annotation.PathVariableMapMethodArgumentResolver@1ab75e8d,
org.springframework.web.servlet.mvc.method.annotation.MatrixVariableMethodArgumentResolver@7ca088ae,
org.springframework.web.servlet.mvc.method.annotation.MatrixVariableMapMethodArgumentResolver@f6d976e,
org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor@63f0beab,
org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor@5275ffcf,
org.springframework.web.servlet.mvc.method.annotation.RequestPartMethodArgumentResolver@40ed9954,
org.springframework.web.method.annotation.RequestHeaderMethodArgumentResolver@2eed7b19,
org.springframework.web.method.annotation.RequestHeaderMapMethodArgumentResolver@692cbe60,
org.springframework.web.servlet.mvc.method.annotation.ServletCookieValueMethodArgumentResolver@7886c691,
org.springframework.web.method.annotation.ExpressionValueMethodArgumentResolver@58569768,
org.springframework.web.servlet.mvc.method.annotation.ServletRequestMethodArgumentResolver@1cee5a27,
org.springframework.web.servlet.mvc.method.annotation.ServletResponseMethodArgumentResolver@6460c547,
org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor@d37ebcd,
org.springframework.web.servlet.mvc.method.annotation.RedirectAttributesMethodArgumentResolver@5259e682,
org.springframework.web.method.annotation.ModelMethodProcessor@c2c8b0b,
org.springframework.web.method.annotation.MapMethodProcessor@405c856b,
org.springframework.web.method.annotation.ErrorsMethodArgumentResolver@7a3b54cf,
org.springframework.web.method.annotation.SessionStatusMethodArgumentResolver@4d3d20ba,
org.springframework.web.servlet.mvc.method.annotation.UriComponentsBuilderMethodArgumentResolver@682fbaf3,
com.catt.web.springmvc.RequestMapResolver@159adcf5,
org.springframework.web.method.annotation.RequestParamMethodArgumentResolver@6a2063e7,
org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor@747f091f]

 

紅色標註出來的RequestParamMapMethodArgumentResolver爲處理Map參數的解析器，處理關鍵代碼：

    public boolean supportsParameter(MethodParameter parameter) {
        RequestParam requestParamAnnot = parameter.getParameterAnnotation(RequestParam.class);
        if (requestParamAnnot != null) {
            if (Map.class.isAssignableFrom(parameter.getParameterType())) {
                return !StringUtils.hasText(requestParamAnnot.value());
            }
        }
        return false;
    }

Map.class.isAssignableFrom會攔截實現Map接口的參數，因此我自定義的解析器始終沒法斷點進入。