如何用Swashbuckle聚合多API端点为单个Swagger文档并通过网关代理？

Hey there! Let's walk through how to aggregate multiple API endpoints into a single Swagger document using Swashbuckle, while ensuring all requests go through your gateway proxy. I've broken this down into actionable steps that should cover your needs:

1. Configure Swashbuckle to Aggregate Remote Swagger Documents #

First, each of your individual APIs needs to generate its own Swagger JSON (via Swashbuckle). Then your gateway will pull these JSON files and merge them into one unified document.

• Step 1: Setup Swashbuckle on Individual APIs
  Make sure every API exposes its Swagger JSON at a standard endpoint (e.g., /swagger/v1/swagger.json). For each API, set a unique Title and Version in their Swashbuckle config to avoid naming conflicts during merging:

  services.AddSwaggerGen(c =>
  {
      c.SwaggerDoc("v1", new OpenApiInfo { Title = "User Service API", Version = "v1" });
  });
  

• Step 2: Pull & Merge Documents in the Gateway
  Install Swashbuckle.AspNetCore in your gateway project, then configure the Swagger generator to reference remote API documents. You can use the built-in RemoteReference method, or manually fetch and merge for more control:

  services.AddSwaggerGen(c =>
  {
      // Define your gateway's own Swagger doc (if it has local endpoints)
      c.SwaggerDoc("aggregated", new OpenApiInfo { Title = "Aggregated Gateway API", Version = "v1" });
  
      // Add references to remote API Swagger docs
      c.RemoteReference("user-service", "https://user-service.example.com/swagger/v1/swagger.json");
      c.RemoteReference("order-service", "https://order-service.example.com/swagger/v1/swagger.json");
  
      // Resolve schema name conflicts by using full type names
      c.CustomSchemaIds(type => type.FullName?.Replace(".", "_") ?? type.Name);
  });
  

  If you need more flexibility (like modifying paths before merging), you can manually fetch each Swagger JSON via HttpClient, parse it into an OpenApiDocument, then merge paths/schemas into the gateway's document.

2. Configure Gateway Proxy Routing #

Next, ensure all API requests are routed through your gateway. Below is an example using YARP (a popular .NET reverse proxy), but the logic applies to other gateways like Ocelot too.

• Setup Routing Rules
  Add route configurations to your gateway's appsettings.json to map gateway paths to backend APIs:

  "ReverseProxy": {
    "Routes": {
      "user-service-route": {
        "ClusterId": "user-service-cluster",
        "Match": {
          "Path": "/user-service/{**catch-all}"
        }
      },
      "order-service-route": {
        "ClusterId": "order-service-cluster",
        "Match": {
          "Path": "/order-service/{**catch-all}"
        }
      }
    },
    "Clusters": {
      "user-service-cluster": {
        "Destinations": {
          "user-service": {
            "Address": "https://user-service.example.com/"
          }
        }
      },
      "order-service-cluster": {
        "Destinations": {
          "order-service": {
            "Address": "https://order-service.example.com/"
          }
        }
      }
    }
  }
  

• Adjust Swagger Paths to Match Gateway Routes
  The remote API's original paths (e.g., /api/users) need to be prefixed with the gateway's route path (e.g., /user-service/api/users). Use a DocumentFilter to modify paths during Swagger generation:

  public class PathPrefixFilter : IDocumentFilter
  {
      private readonly string _prefix;
  
      public PathPrefixFilter(string prefix) => _prefix = prefix;
  
      public void Apply(OpenApiDocument swaggerDoc, DocumentFilterContext context)
      {
          var updatedPaths = new OpenApiPaths();
          foreach (var (pathKey, pathItem) in swaggerDoc.Paths)
          {
              updatedPaths.Add(_prefix + pathKey, pathItem);
          }
          swaggerDoc.Paths = updatedPaths;
      }
  }
  

  Register this filter for each remote API in your gateway's Swashbuckle config:

  c.DocumentFilter<PathPrefixFilter>("/user-service"); // Prefix for user service paths
  c.DocumentFilter<PathPrefixFilter>("/order-service"); // Prefix for order service paths
  

3. Handle Authentication & Authorization #

If your APIs use authentication (e.g., JWT), ensure the gateway handles it uniformly and passes credentials to backend services.

• Configure Swagger UI for Authentication
  Enable OAuth/JWT support in the gateway's Swagger UI so users can authenticate and send valid requests:

  app.UseSwaggerUI(c =>
  {
      c.SwaggerEndpoint("/swagger/aggregated/swagger.json", "Aggregated Gateway API");
      c.OAuthClientId("your-gateway-client-id");
      c.OAuthAppName("Gateway Aggregated API");
      c.OAuthUsePkce();
  });
  

• Forward Authentication Headers
  Configure your gateway proxy to forward the Authorization header (or other auth headers) to backend APIs. For YARP, this is enabled by default, but double-check your proxy settings to ensure headers aren't stripped.

4. Test & Debug #

• Start all backend APIs and the gateway, then visit the gateway's Swagger UI (typically at /swagger). You should see all aggregated endpoints from every API.
• Test each endpoint to confirm requests are routed correctly through the gateway and return valid responses.
• If you hit schema name conflicts, tweak the CustomSchemaIds logic to ensure unique names for all models across APIs.

内容的提问来源于stack exchange，提问作者Gayan