1.前言

前端與後端的聯絡更多是通過API介面對接，API文件變成了前後端開發人員聯絡的紐帶，開始變得越來越重要，而Swagger就是一款讓你更好的書寫規範API文件的框架。在Ocelot Swagger專案示例中，通過APIGateway專案路由配置閘道器、上下游服務Swagger。對解決方案中的示例APIServiceA、APIServiceB專案Get方法進行配置，檔案配置具體程式碼如下：

{
  "Routes": [
    {
      //下游服務地址
      "DownstreamPathTemplate": "/swagger/v1/swagger.json",
      //傳輸協議
      "DownstreamScheme": "http",
      //下游主機跟埠號（陣列）
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 9001
        }
      ],
      //上游服務地址
      "UpstreamPathTemplate": "/a/swagger.json",
      //上游服務Http埠號（陣列）
      "UpstreamHttpMethod": [ "Get", "POST" ]
    },
    {
      "DownstreamPathTemplate": "/swagger/v1/swagger.json",
      "DownstreamScheme": "http",
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 9002
        }
      ],
      "UpstreamPathTemplate": "/b/swagger.json",
      "UpstreamHttpMethod": [ "Get", "POST" ]
    },
    {
      "DownstreamPathTemplate": "/api/values",
      "DownstreamScheme": "http",
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 9001
        }
      ],
      "UpstreamPathTemplate": "/a",
      "UpstreamHttpMethod": [ "Get" ]

    },
    {
      "DownstreamPathTemplate": "/api/values",
      "DownstreamScheme": "http",
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 9002
        }
      ],
      "UpstreamPathTemplate": "/b",
      "UpstreamHttpMethod": [ "Get" ]

    }
  ],
  "GlobalConfiguration": {
    "RequestIdKey": "OcRequestId",
    "AdministrationPath": "/administration"
  }
}

2.專案演示

2.1APIGateway專案

新增Ocelot、Swagger服務注入：

public static IWebHost BuildWebHost(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
            .UseUrls("http://*:9000")
        .ConfigureAppConfiguration((hostingContext, config) =>
        {
            config
                .SetBasePath(hostingContext.HostingEnvironment.ContentRootPath)
                .AddJsonFile("ocelot.json")
                .AddEnvironmentVariables();
        })
        .ConfigureServices(s =>
        {
            //新增Ocelot服務；
            s.AddOcelot();
            s.AddMvc();
            //新增Swagger服務；
            s.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "GW", Version = "v1" });
                var basePath = PlatformServices.Default.Application.ApplicationBasePath;
                var xmlPath = Path.Combine(basePath, "APIGateway.xml");
                c.IncludeXmlComments(xmlPath);
            });
        })
        .Configure(a =>
        {
            //使用Swagger
            a.UseSwagger().UseSwaggerUI(c =>
            {
                c.SwaggerEndpoint("/a/swagger.json", "APIServiceA");
                c.SwaggerEndpoint("/b/swagger.json", "APIServiceB");
            });

            //使用Ocelot；
            a.UseOcelot().Wait();
        })
        .Build();

2.2APIServiceA專案

Startup新增Swagger服務注入：
ConfigureServices：

services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "APIServiceA", Version = "v1" });
    var basePath = PlatformServices.Default.Application.ApplicationBasePath;
    var xmlPath = Path.Combine(basePath, "APIServiceA.xml");
    c.IncludeXmlComments(xmlPath);
});
Configure：
app.UseSwagger();
app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("/swagger/v1/swagger.json", "APIServiceA");
});

新增一個Get方法，對應APIGateway專案的路由上下游配置，具體程式碼如下：

/// <summary>
/// Values controller.
/// </summary>
[Route("api/[controller]")]
public class ValuesController : Controller
{
    // GET api/values
    /// <summary>
    /// Get values.
    /// </summary>
    /// <returns>The get.</returns>
    [HttpGet]
    public IEnumerable<string> Get()
    {
        return new string[] { "value1", "value2" };
    }
}

2.3APIServiceB專案

Startup新增Swagger服務注入：
ConfigureServices：

services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "APIServiceB", Version = "v1" });
    var basePath = PlatformServices.Default.Application.ApplicationBasePath;
    var xmlPath = Path.Combine(basePath, "APIServiceB.xml");
    c.IncludeXmlComments(xmlPath);
});

Configure：

app.UseSwagger();
app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("/swagger/v1/swagger.json", "APIServiceB");
});

新增一個Get方法，對應APIGateway專案的路由上下游配置，具體程式碼如下：

/// <summary>
/// Values controller.
/// </summary>
[Route("api/[controller]")]
public class ValuesController : Controller
{
    // GET api/values
    /// <summary>
    /// Get values.
    /// </summary>
    /// <returns>The get.</returns>
    [HttpGet]
    public IEnumerable<string> Get()
    {
        return new string[] { "value3", "value4" };
    }
}

2.4專案執行

注：如果想把Swagger註釋警告提示取消，可以在對應專案檔案.csproj的PropertyGroup節點上加入<NoWarn>$(NoWarn);1591</NoWarn>這一行程式碼。
輸入dotnet run --project 專案路徑\專案檔案.csproj把三個專案啟動起來，通過在瀏覽器分別開啟APIServiceA與APIServiceB兩個站點上游服務Swagger地址，會看到如下資訊：
APIServiceA：

APIServiceB：

通過閘道器的路由配置，把Swagger整合到Ocelot中，統一入口管理，通過閘道器入口我們就能開啟不同下游服務的Swagger。這一系列章節都是Ocelot入門級別的文章，最後章節將會來介紹Ocelot結合Consul的服務發現。