如何理解asp.netmvccore管道及拦截器-创新互联
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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。
总结
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