自定义ASP.NET Core日志中间件

　　这个日志框架使用的是ASP.NET Core的NLog，用来记录每次请求信息和返回信息。

1.首先创建一个Web应用项目，我选择的是MVC模板：

2.使用NuGet添加Microsoft.Extensions.Logging和NLog.Extensions.Logging

3.修改Configure方法：

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
loggerFactory.AddNLog(); //添加NLog
NLog.LogManager.LoadConfiguration("nlog.config");
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();

app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}");
});
}

4.添加nlog.config配置文件，内容如下：

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
autoReload="true"
internalLogLevel="Warn"
internalLogFile="internal-nlog.txt">

<!--define various log targets-->
<targets>

<!--write logs to file-->
<target xsi:type="File" name="allfile" fileName="nlog-all-${shortdate}.log"
layout="${longdate}|${logger}|${uppercase:${level}}|${message} ${exception}" />

<target xsi:type="File" name="ownFile-web" fileName="nlog-my-${shortdate}.log"
layout="${longdate}|${logger}|${uppercase:${level}}|${message} ${exception}" />

<target xsi:type="Null" name="blackhole" />

</targets>

<rules>
<!--All logs, including from Microsoft-->
<logger name="*" minlevel="Trace" writeTo="allfile" />

<!--Skip Microsoft logs and so log only own logs-->
<logger name="Microsoft.*" minlevel="Trace" writeTo="blackhole" final="true" />
<logger name="*" minlevel="Trace" writeTo="ownFile-web" />
</rules>
</nlog>

　　注意：运行项目时需要复制nlog.config到debug

5.接下来开始自定义中间件

　　添加一个LogMiddleware类：

public class LogMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger<LogMiddleware> _logger;
public LogMiddleware(RequestDelegate next, ILogger<LogMiddleware> logger)
{
_next = next;
_logger = logger;
}

public async Task Invoke(HttpContext context)
{
_logger.LogInformation("Request Url:" + context.Request.Path +Environment.NewLine
+ "Body:" + context.Request.Body.ToString());
await _next.Invoke(context);
_logger.LogInformation("Response Url:" + context.Request.Path + Environment.NewLine
+ "Body:" + context.Response.Body.ToString());
}
}

　　再创建一个LogMiddlewareExtensions类：

/// <summary>
/// 这是扩展中间件
/// </summary>
public static class LogMiddlewareExtensions
{
public static IApplicationBuilder UseLog(this IApplicationBuilder builder)
{
return builder.UseMiddleware<LogMiddleware>();
}
}

　　这样就编写好一个自定义的中间件。

6.在Configure方法中调用app.UseLog()

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
loggerFactory.AddNLog(); //添加NLog
NLog.LogManager.LoadConfiguration("nlog.config");
app.UseLog();
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();

app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}");
});
}

运行代码，会在debug文件下生成日志文件。