ASP.NET MVC 通过ActionFilter 实现AOP设计示例

分手后的思念是犯贱 2022-07-15 07:59 118阅读 0赞

在Asp.Net MVC 框架中我们可以通过ActionFilter来拦截请求，并对请求做一定处理后再交于Action做数据处理。此外，也可以利用ActionFilter来对Action的返回值做统一处理，再返回给客户端调用。同ActionFilter的合理利用，能够很容易实现AOP设计，达到代码隔离的效果。 在这里分享一个示例，以供交流学习。

在该示例中，实现了 数据流拦截 和 参数的注入。

public class MyIntercepterAttribute : FilterAttribute, IActionFilter
        {
            private const string nodeName = "someNode";
            public void OnActionExecuting(ActionExecutingContext actionContext)
            {
                var inputStream = actionContext.HttpContext.Request.InputStream;
                inputStream.Position = 0;
                string payloadStr;
                using (var streamReader = new StreamReader(inputStream))
                {
       //读取原有数据
                    payloadStr = streamReader.ReadToEnd();
                }
    
                if (string.IsNullOrWhiteSpace(payloadStr))
                {
                    throw new HttpException(400, "Invalid payload");
                }
    
                var wrapper = (JObject)JsonConvert.DeserializeObject(payloadStr);
                var originalDataNode = wrapper[nodeName];
    
                if (originalDataNode == null)
                {
                    throw new HttpException(400, "Invalid schema.");
                }
    
                //将原始字符串解析为Json 数据方便做进一步处理。
                var plainRequest = originalDataNode.ToObject<string>();
                var requestRootNode = (JObject)JsonConvert.DeserializeObject(plainRequest);
    
                var parameters = actionContext.ActionDescriptor.GetParameters();
                var jsonSerializer = new JsonSerializer { ContractResolver = new CamelCasePropertyNamesContractResolver() };
                foreach (var param in parameters)
                {
       //根据需求 构造/转化 Action 的参数
                    JToken matchedParamNode;
                    requestRootNode.TryGetValue(param.ParameterName, StringComparison.CurrentCultureIgnoreCase, out matchedParamNode) ;
                    if (matchedParamNode != null)
                    {
                        actionContext.ActionParameters[param.ParameterName] = matchedParamNode.ToObject(param.ParameterType, jsonSerializer);
                    }
                    else if (param.ParameterType.IsClass && param.ParameterType != typeof(string))
                    {
                        actionContext.ActionParameters[param.ParameterName] = requestRootNode.ToObject(param.ParameterType, jsonSerializer);
                    }
                }
            }
    
            public void OnActionExecuted(ActionExecutedContext filterContext)
            {
                var result = filterContext.Result;
                if (result is JsonResult)
                {
       //转换 Action的返回值
                    var jsonResult = result as JsonResult;
                    var handledResponse = JsonConvert.SerializeObject(jsonResult.Data);
    
                    jsonResult.Data = new { Result = handledResponse };
                }
                else
                {
                    throw new  NotImplementedException("Currently, this sample only support json result.");
                }
            }
        }