HandlerMethodArgumentResolver数据绑定无效

  因项目中action参数过多，并且是一些通用的查询参数，所以准备进行对参数统一封装为Map对象，然后由action中传入service中进行处理，查询spring的资料发现可以通过实现HandlerMethodArgumentResolver进行数参数的绑定，参考文章《扩展SpringMVC以支持更精准的数据绑定1》进行配置后。

  项目调试中发现断点不能正常进行解析器，跟踪源代码找到在org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.getArgumentResolver()方法中会获取所有已经加载的解析器，会顺序执行，而我使用的Map对象会被spring自带的解析器给处理掉，所以自定义的解析器无法进入，HandlerMethodArgumentResolverComposite关键代码：

    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为LinkedList变量，元素内容：

[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]

 

红色标注出来的RequestParamMapMethodArgumentResolver为处理Map参数的解析器，处理关键代码：

    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会拦截实现Map接口的参数，所以我自定义的解析器始终无法断点进入。