asp.net mvc core管道及拦截器的理解

今天来看一下asp.net core的执行管道。先看下官方说明：

 从上图可以抛光，asp.net core的执行顺序是，当收到一个请求后，request请求会先经过已注册的中间件，然后会进入到mvc的拦截器管道：

进入mvc管道后，根据以上顺序执行过滤校正。

OK，根据以上说明下面我们新建一个MVC的演示，将执行方式切换为控台运行：

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
 services.AddControllersWithViews(config=> 
 {
  Console.WriteLine("execute C");
  //config.Filters.Add(new AsyncAuthorizationFilter());
  config.Filters.Add(new AuthorizationFilter());
  config.Filters.Add(new ResourceFilter());
  //config.Filters.Add(new AsyncResourceFilter());
  config.Filters.Add(new ActionFilter());
  //config.Filters.Add(new AsyncActionFilter());
  config.Filters.Add(new ResultFilter());
  //config.Filters.Add(new AsyncResultFilter());
  config.Filters.Add(new ExceptionFilter());
  //config.Filters.Add(new AsyncExceptionFilter());
  Console.WriteLine("execute D");
 });
 services.AddSession(config=> {
  Console.WriteLine("execute E");
 });
}

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
 if (env.IsDevelopment())
 {
  app.UseDeveloperExceptionPage();
 }
 else
 {
  app.UseExceptionHandler("/Home/Error");
 }
 app.UseStaticFiles();
 app.UseRouting();
 app.UseAuthorization();
 app.Use(async (context, next) =>
 {
  Console.WriteLine("execute F");
  await context.Response.WriteAsync("hello world");
  Console.WriteLine("execute G");
 });
 //app.UseSession();
 app.UseEndpoints(endpoints =>
 {
  Console.WriteLine("execute A");
  endpoints.MapControllerRoute(
   name: "default",
   pattern: "{controller=Home}/{action=Index}/{id?}");
  Console.WriteLine("execute B");
 });
}

执行结果：

不多做解释，从从这里我们可以抛光符合官方说明文档。

看完中间件执行顺序，下面我们来了解下mvc拦截器的使用与执行顺序。

根据mvc filter管道执行顺序，我们分别来看下用法：

1）AuthorizationFilter：该拦截器是优先级最高的，当请求进入mvc后，首先会被AuthorizationFilter验证是否有权限访问，无权限则跳出。

同步用法：

public class AuthorizationFilter: IAuthorizationFilter
{
 public void OnAuthorization(AuthorizationFilterContext context)
 {
  context.HttpContext.Response.WriteAsync("authorization filter \r");
 }
}

异步用法：

public class AsyncAuthorizationFilter: IAsyncAuthorizationFilter
{
 public async Task OnAuthorizationAsync(AuthorizationFilterContext context)
 {
  await context.HttpContext.Response.WriteAsync($"async authorization filter in \r");
 }
}

2）ResourceFilter：该拦截器是作为第二道拦截器，

OnResourceExecuting在模型绑定之前运行代码。OnResourceExecuted在管道的其余阶段完成之后运行代码。

同步用法：

public class ResourceFilter: IResourceFilter
{
 public void OnResourceExecuting(ResourceExecutingContext context)
 {
  context.HttpContext.Response.WriteAsync($"resource executing\r");
 }
 public void OnResourceExecuted(ResourceExecutedContext context)
 {
  context.HttpContext.Response.WriteAsync($"resource executed \r");
 }
}

异步用法：

public class AsyncResourceFilter: IAsyncResourceFilter
{
 public async Task OnResourceExecutionAsync(ResourceExecutingContext context, ResourceExecutionDelegate next)
 {
  await context.HttpContext.Response.WriteAsync($" async resource filter in. \r\n");
  await next();
  await context.HttpContext.Response.WriteAsync($"async resource filter out. \r\n");
 }
}

3）ActionFilter：在调用操作方法之前和之后立即运行代码；可以更改传递到操作中的参数；可以更改从操作返回的结果。

同步用法：

public class ActionFilter: IActionFilter
{
 public void OnActionExecuting(ActionExecutingContext context)
 {
  context.HttpContext.Response.WriteAsync($"action executing \r");
 }

 public void OnActionExecuted(ActionExecutedContext context)
 {
  context.HttpContext.Response.WriteAsync($"action executed . \r");
 }
}

异步用法：

public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
{
 await context.HttpContext.Response.WriteAsync($"async action execution in. \r\n");
 await next();
 await context.HttpContext.Response.WriteAsync($"async action execution out. \r\n");
}

4）OnException：在向响应正文写入任何内容之前，对声明处理的异常应用变量策略。

同步用法：

public class ExceptionFilter: IExceptionFilter
{
 public void OnException(ExceptionContext context)
 {
  context.HttpContext.Response.WriteAsync($"exception \r");
 }
}

异步用法：

public class AsyncExceptionFilter: IAsyncExceptionFilter
{
 public Task OnExceptionAsync(ExceptionContext context)
 {
  context.HttpContext.Response.WriteAsync($"exception async \r");
  return Task.CompletedTask;
 }
}

5）ResultFilter：在执行操作结果之前和之后立即运行代码；仅当操作方法成功执行时，其才会运行。 可以设置格式化返回结果：

同步操作：

public class ResultFilter: IResultFilter
{
 public void OnResultExecuting(ResultExecutingContext context)
 {
  context.HttpContext.Response.WriteAsync($"result executing\r");
 }
 public void OnResultExecuted(ResultExecutedContext context)
 {
  context.HttpContext.Response.WriteAsync($"result executed \r");
 }
}

异步用法：

public class AsyncResultFilter: IAsyncResultFilter
{
 public async Task OnResultExecutionAsync(ResultExecutingContext context, ResultExecutionDelegate next)
 {
  await context.HttpContext.Response.WriteAsync($"result execution async in \r");
  await next();
  await context.HttpContext.Response.WriteAsync($"result execution async out. \r");
 }
}

注册方式我们就是用分区注册，已经在上面说明，不再多做表述，下面我们看下运行情况（页面输出）：

 定义一个异常看下结果：

public IActionResult Privacy()
{
  throw new Exception("error");
}

ok，目标达成，不多说了，下次再看拦截器具体实现。

参考文档：ASP.NET Core 中的筛选器

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