vue调用后端接口下载demo

　　红花还得绿叶陪衬。vue前端开发离不开数据，这数据正来源于请求web api。为什么采用.net core web api呢？因为考虑到跨平台部署的问题。即使眼下部署到window平台，那以后也可以部署到Linux下。

　　.net core web api与mvc的web api类似。我把遇到的问题归纳下：

1、部署问题

都说.net core web api，后面我简称api。它有两种部署方式，一个是在iis上部署，另外一个是自托管，类似控制台，通过dotnet  run 命令启动的。

 1.1 自托管部署

dotnet myapp.dll

网上说，通过hosting.json

{
  "server.urls": "http://localhost:60000;http://localhost:60001"
}

这种方式有个问题，在配置了urls，并没有走配置。

public static void Main(string[] args)
{
    var config = new ConfigurationBuilder()
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("hosting.json", optional: true)
        .Build();

    var host = new WebHostBuilder()
        .UseKestrel()
        .UseConfiguration(config)
        .UseContentRoot(Directory.GetCurrentDirectory())
        .UseIISIntegration()
        .UseStartup<Startup>()
        .Build();

    host.Run();
}

不过人家是说在Linux环境下的部署，我在window下测试是不行的，不知道是哪的问题，后面可以再研究。

1.2、iis上部署

必须首先安装AspNetCoreModule,搜索这个模块，它的描述如下：

The ASP.NET Core Module allows ASP.NET Core apps to run in an IIS worker process (in-process) or behind IIS in a reverse proxy configuration (out-of-process). IIS provides advanced web app security and manageability features. 

这句话大意：api有两种运行模式，一种是运行在iis工作进程中（In-process hosting model），另外一种是通过反向代理配置，运行在外（Out-of-process hosting model）。具体，可参考官方文档。

 

这是文档中 In-process hosting model图，我们可以看出，http请求首先到达kernel-mode HTTP.sys driver，http监听器，监听器把请求给iis，首先是Asp.NET Core Module接受，然后传递给IISHttpServer，它把请求转换为托管代码，进入.net core middelware pipline,最后才是我们的api代码。换句话说，Asp.NET Core Module类似中间件的作用，它先处理的一部分事情。这是我们项目中采取的部署方案，另外一种模式可能比较复杂，大家阅读官方文档。

2、全局异常处理

我们知道mvc中，有两种异常处理：

使用Global.asax的Application_Error事件进行全局异常处理以及使用HandleErrorAttribute特性捕获全局异常

.net core api中可以编写异常处理的中间件，如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json; 
using System; 
using System.Collections.Generic; 
using System.IO; 
using System.Linq; 
using System.Net; 
using System.Threading.Tasks; 
using System.Xml.Serialization; 

namespace ElectronInfoApi.Business {
    public class GlobalExceptionMiddleware {
        private  readonly RequestDelegate next;
        public GlobalExceptionMiddleware(RequestDelegate next) {
            this.next = next; 
        }

        public async Task Invoke(HttpContext context) {
            try {
                await next(context); 
            }
            catch (Exception ex) {
                await HandleExceptionAsync(context, ex); 
            }
        }

        private  async Task HandleExceptionAsync(HttpContext context, Exception exception) {
            if (exception == null)return; 
            await WriteExceptionAsync(context, exception).ConfigureAwait(false); 
        }

        private  async Task WriteExceptionAsync(HttpContext context, Exception exception) {
            //记录日志
             this.Log().Error($"系统发生了异常：{exception.Message}, {exception.StackTrace}");
            //返回友好的提示
            var response = context.Response; 

            //状态码
            if (exception is UnauthorizedAccessException)
                response.StatusCode = (int)HttpStatusCode.Unauthorized; 
            else if (exception is Exception)
                response.StatusCode = (int)HttpStatusCode.BadRequest; 

            response.ContentType = context.Request.Headers["Accept"];

            response.ContentType = "application/json"; 
            await response.WriteAsync(JsonConvert.SerializeObject(new {state=400,message="出现未知异常"})).ConfigureAwait(false); 
        }

    }

     public static class VisitLogMiddlewareExtensions
    {
        public static IApplicationBuilder UseGlobalException(this IApplicationBuilder builder)
        {
            return builder.UseMiddleware<GlobalExceptionMiddleware>();
        }
    }
}

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在startup>Configure中添加

app.UseGlobalException();

官网有文档，是这么定义中间件的：

Middleware is software that's assembled into an app pipeline to handle requests and responses

3、安全验证

接口验证，是为了安全性考虑，采用Jwt(Json web token)。

第一步，添加包引用：

<PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="2.1.2" />

第二步，配置：

"Issuer": "ElectronInfo",
 "Audience": "ElectronInfo",
 "SecretKey": "ElectronInfo is a web of shanxi dianzi qingbao weiyuanhui"

第三步，在Startup>ConfigureServices中添加授权服务：

var jwtSettings = new JwtSettings(){
                Issuer=AppSetting.GetConfig("Issuer"),
                Audience=AppSetting.GetConfig("Audience"),
                SecretKey=AppSetting.GetConfig("SecretKey"),
            };

      services.AddAuthentication(options =>  {
          options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme; 
          options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme; 
         })
        .AddJwtBearer(o =>  {
           o.TokenValidationParameters = new Microsoft.IdentityModel.Tokens.TokenValidationParameters {
           ValidIssuer = jwtSettings.Issuer, 
           ValidAudience = jwtSettings.Audience, 
           IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(jwtSettings.SecretKey)),
　　　　　　 ValidateIssuerSigningKey = true, 
           ValidateIssuer = true,
　　　　　　 ValidateLifetime = true, 
　　　　　　 ClockSkew = TimeSpan.Zero
           }; 
        });

第四步：在Startup>Configure中添加

app.UseAuthentication();

第五步：给整个Controller或者需要接口验证的action中添加

[Authorize]

附：AppSetting类，读取appsettings.json，如下：

using System.IO; 
using Microsoft.Extensions.Configuration; 

namespace ElectronInfoApi.Business {
public class AppSetting {
    private static readonly object objLock = new object(); 
    private static AppSetting instance = null; 

    private IConfigurationRoot Config {get; }

    private AppSetting() {
        var builder = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json", optional:false, reloadOnChange:true); 
        Config = builder.Build(); 
    }

    public static AppSetting GetInstance() {
        if (instance == null) {
            lock (objLock) {
                if (instance == null) {
                    instance = new AppSetting(); 
                }
            }
        }

        return instance; 
    }

    public static string GetConfig(string name) {
        return GetInstance().Config.GetSection(name).Value; 
    }
}}

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4、日志log4

    .net core中本来就支持console输出日志。不过今天我要说的是log4，在传统的.net中普遍使用。

    第一步，添加包引用：

<PackageReference Include="log4net" Version="2.0.8" />

  第二步，添加配置文件log4net.config：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <!-- This section contains the log4net configuration settings -->
  <log4net>
    <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender">
      <layout type="log4net.Layout.PatternLayout" value="%date [%thread] %-5level %logger - %message%newline" />
    </appender>
    
    <!--<appender name="FileAppender" type="log4net.Appender.FileAppender">
      <file value="log-file.log" />
      <appendToFile value="true" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
    </appender> -->

    <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="logfile/" />
      <appendToFile value="true" />
      <rollingStyle value="Composite" />
      <staticLogFileName value="false" />
      <datePattern value="yyyyMMdd'.log'" />
      <maxSizeRollBackups value="10" />
      <maximumFileSize value="1MB" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
    </appender>

    <!-- Setup the root category, add the appenders and set the default level -->
    <root>
      <level value="ALL" />
      <appender-ref ref="ConsoleAppender" />
      <!--<appender-ref ref="FileAppender" />-->
      <appender-ref ref="RollingLogFileAppender" />
    </root>

  </log4net>
</configuration>

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第三步，包装以及扩展log4，为了更方便使用：

首先定义一个接口IMLog：

using System; 

namespace ElectronInfoApi.Business {
public interface IMLog {
    // Methods
    void Debug(string message); 
    void Error(string message, Exception exception); 
    void Error(string message); 
    void Fatal(string message); 
    void Info(string message); 
    void Warn(string message); 
}
public interface IMLog < T >  {
    
}

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再定义包装器Log4NetWapper：

using System; 
using log4net; 
using log4net.Core; 

namespace ElectronInfoApi.Business {
    public class Log4NetWapper:IMLog, IMLog < Log4NetWapper >  {

         private ILog  _logger; 

           public Log4NetWapper(string loggerName) {
        this._logger = LogManager.GetLogger(Startup.repository.Name, loggerName); 
    }

        public void Debug(string message) {
            _logger.Debug(message); 
        }


        public void Error(string message, Exception exception) {
            _logger.Error(message, exception); 
        }

        public void Error(string message) {
            _logger.Error(message); 
        }

        public void Fatal(string message) {
            _logger.Fatal(message); 
        }

        public void Info(string message) {
            _logger.Info(message); 
        }

        public void Warn(string message) {
            _logger.Warn(message); 
        }
    }


}

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最后定义扩展方法 LogExtensions：

using System.Collections.Concurrent; 

namespace ElectronInfoApi.Business {
public static class LogExtensions {
    // Fields
    private static readonly ConcurrentDictionary < string, IMLog > _dictionary = new ConcurrentDictionary < string, IMLog > (); 

    // Methods
    public static IMLog Log(this string objectName) {
        if ( ! _dictionary.ContainsKey(objectName)) {
            IMLog log = new Log4NetWapper(objectName); 
            _dictionary.TryAdd(objectName, log); 
        }
        return _dictionary[objectName]; 
    }

    public static IMLog Log < T > (this T type) {
        return typeof(T).FullName.Log(); 
    }
}}

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第四步，在Startup中使用：

public static ILoggerRepository repository {get; set; }

 public Startup(IConfiguration configuration) {
     repository = LogManager.CreateRepository("NETCoreRepository"); 
     XmlConfigurator.Configure(repository, new FileInfo("log4net.config"));   
     Configuration = configuration; 
 }
 public IConfiguration Configuration {get; }

5、.对net core中startup理解，见官方文档

好了，关于.net core api也是第一次正式使用，就总结到这里。