一、ASP.NET Core 中间件简介
中间件是一种装配到应用程序管道以处理请求和响应的软件。 每个组件可进行以下操作：
选择是否将请求传递到管道中的下一个组件。
可在调用管道中的下一个组件前后执行工作。
中间件在请求过程中执行顺序示意图：
二、ASP.NET Core中间件开发和使用
1、新建项目、项目基础功能配置
1.1 新建asp.net core web 应用程序
1.2 将 Properties/launchSettings.json 文件中两处端口号 都改为5000，一个是vs（iis）运行时的端口号，一个是直接命令行（dotnet run）运行时的端口号
1.3 Huanent.Logging.File包用来记录日志
安装nuget包：Huanent.Logging.File（依赖项：Microsoft.Extensions.Logging.Console） 用来记录文本日志和console日志
（源码在：https://github.com/huanent/Huanent.Logging）
在根目录加配置文件：appsettings.json，内容：
{
"Logging": {
"IncludeScopes": false,
"Debug": {
"LogLevel": {
"Default": "Warning"
}
},
"Console": {
"LogLevel": {
"Default": "Warning"
}
},
"File": {
"LogLevel": {
"Default": "Information"
}
}
}
}修改 Startup.cs，方法Configure 加参数 ILoggerFactory loggerFactory，然后在方法内部加代码：
loggerFactory.AddConsole(minLevel: LogLevel.Information);//启用控制台输出log中间件
修改Program.cs，在 .Build() 前面，加一行代码：
.ConfigureLogging(builder => builder.AddFile())//启用文本日志
2、开发中间件示例
2.1 记录请求者IP中间件开发（带输入参数）
中间件类：RequestIPMiddleware.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
namespace MiddleWareTest
{
/// <summary>
/// 模拟记录请求者IP、请求Path中间件
/// </summary>
public class RequestIPMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger _logger;
private readonly RequestIPOptions _option;
public RequestIPMiddleware(RequestDelegate next, ILoggerFactory loggerFactory, IOptions<RequestIPOptions> options)
{
_next = next;
_logger = loggerFactory.CreateLogger<RequestIPMiddleware>();
if (options != null)
{
_option = options.Value;
}
}
public async Task Invoke(HttpContext context)
{
if (context.Request.Path.HasValue && context.Request.Path.Value != "/favicon.ico")
{
var ip = context.Connection.RemoteIpAddress.ToString();
if (_option == null || _option.LogType == 0 || (ip != "127.0.0.1" && ip != "::1"))
_logger.LogInformation("User IP：{0},path：{1}", ip, context.Request.Path);
}
await _next.Invoke(context);
}
}
public static class RequestIpExtensions
{
public static IApplicationBuilder UseRequestIP(this IApplicationBuilder app)
{
if (app == null)
{
throw new ArgumentNullException(nameof(app));
}
return app.UseMiddleware<RequestIPMiddleware>();
}
public static IApplicationBuilder UseRequestIP(this IApplicationBuilder app, RequestIPOptions options)
{
if (app == null)
{
throw new ArgumentNullException(nameof(app));
}
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
return app.UseMiddleware<RequestIPMiddleware>(Options.Create(options));
}
}
}参数类：RequestIPOptions.cs
using Microsoft.Extensions.Options;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace MiddleWareTest
{
public class RequestIPOptions : IOptions<RequestIPOptions>
{
/// <summary>
/// 记录类型，0：默认全部，1：非local请求
/// </summary>
public int LogType { get; set; }
RequestIPOptions IOptions<RequestIPOptions>.Value
{
get
{
return this;
}
}
}
}2.2 权限验证中间件开发
MyAuthMiddleware.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
namespace MiddleWareTest
{
/// <summary>
/// 模拟权限验证中间件
/// </summary>
public class MyAuthMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger _logger;
public MyAuthMiddleware(RequestDelegate next, ILoggerFactory loggerFactory)
{
_next = next;
_logger = loggerFactory.CreateLogger<MyAuthMiddleware>();
}
public async Task Invoke(HttpContext context)
{
if (context.Request.Path.HasValue)
{
if(context.Request.Path.Value == "/favicon.ico")
{
return;
}
//这里模拟用户无权限访问
if (context.Request.Path.Value == "/Forbidden")
{
_logger.LogInformation("禁止访问");
context.Response.StatusCode = (int)HttpStatusCode.Forbidden;//可以直接返回状态码
//context.Response.Redirect("/403.html");//直接跳转到提示页
return;
}
//这里模拟用户请求报错
else if (context.Request.Path.Value == "/InternalServerError")
{
_logger.LogInformation("服务器错误");
context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;//可以直接返回状态码
//context.Response.Redirect("/500.html");//直接跳转到提示页
return;
}
else
{
_logger.LogInformation("权限正常");
}
//验证通过，走正常流程（不阻碍正常流程）
}
await _next.Invoke(context);
}
}
public static class MyAuthExtensions
{
public static IApplicationBuilder UseMyAuth(this IApplicationBuilder app)
{
if (app == null)
{
throw new ArgumentNullException(nameof(app));
&nb