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

总结

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