Swagger / OpenAPI in Lambda project

[timhill-iress]

I've a question about Swagger-UI and AWS Lambda, I'm not sure if it's a bug or not.

I've noticed that if I generate a project using micronaut launch with OpenAPI and Swagger-UI alongside the AWS Lambda Feature
mn create-app --build=gradle_kotlin --jdk=11 --lang=kotlin --test=junit --features=aws-lambda,openapi,swagger-ui com.example.demo
that when run the application the swagger yml and swagger-ui are not available - http://localhost:8080/swagger-ui gives a 404 with

{
"message": "Not Found",
"_links": {
"self": {
"href": "https://null.execute-api.us-east-1.amazonaws.com/swagger-ui",
"templated": false
}
},
"_embedded": {
"errors": [
{
"message": "Page Not Found"
}
]
}
}

If I change build.gradle.kts
from

micronaut {
    runtime("lambda")

to

micronaut {
    runtime("netty")

Then http://localhost:8080/swagger-ui works fine.

Is this a known issue? I couldn't find any mention of it in the docs. Is there a reason why it can't work? Or is it just a bug?

[timhill-iress]

I've found this is already raised as an issue in the micronaut-aws project - micronaut-projects/micronaut-aws#1361

[sjesubillgo]

To access Swagger UI from Lambda using Micronaut, we took the following approach. This is tested using AWS API Gateway & working fine & don't find any issues so far:

• Created Controller class to read swagger.yml, Index.html, JS & CSS file
• Created Four controller methods/APIs:
  1. For accessing swagger.yml
  2. For accessing CSS & Javascript files
  3. For accessing PNG files
  4. For accessing Index.html

import io.micronaut.core.io.scan.ClassPathResourceLoader;
import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.PathVariable;
import io.micronaut.http.annotation.Produces;
import jakarta.annotation.Nullable;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.Optional;
import org.apache.commons.io.IOUtils;

@Controller(
    produces = {
      MediaType.APPLICATION_YAML,
      MediaType.TEXT_HTML,
      MediaType.IMAGE_PNG,
      "text/css",
      "text/javascript"
    })
public class SwaggerController {

  private static final String SWAGGER_UI_RESOURCE_LOCATION = "classpath:META-INF/swagger/views/swagger-ui/res/";
  private final ClassPathResourceLoader loader;

  public SwaggerController(ClassPathResourceLoader loader) {
    this.loader = loader;
  }

  @Get("/swagger-ui/res{/path:.*}{.ext:png}")
  @Produces(MediaType.IMAGE_PNG)
  public byte[] getSwaggerUiImage(
      @PathVariable @Nullable String path, @PathVariable @Nullable String ext) throws IOException {
    Optional<URL> resource = loader.getResource(SWAGGER_UI_RESOURCE_LOCATION + path + "." + ext);
    return IOUtils.toByteArray(resource.orElseThrow().openStream());
  }

  @Get("/swagger-ui/res{/path:.*}{.ext:css|js}")
  @Produces({"text/css", "text/javascript"})
  public String getSwaggerLibrary(
      @PathVariable @Nullable String path, @PathVariable @Nullable String ext) throws IOException {
    Optional<URL> resource = loader.getResource(SWAGGER_UI_RESOURCE_LOCATION + path + "." + ext);
    return IOUtils.toString(
        (BufferedInputStream) resource.orElseThrow().getContent(), StandardCharsets.UTF_8);
  }

  @Get("/api/directory/swagger-ui")
  @Produces(MediaType.TEXT_HTML)
  public String getSwaggerIndexPage() throws IOException {
    Optional<URL> resource =
        loader.getResource("classpath:META-INF/swagger/views/swagger-ui/index.html");
    return IOUtils.toString(
        (BufferedInputStream) resource.orElseThrow().getContent(), StandardCharsets.UTF_8);
  }

  @Get("/swagger/swagger.yml")
  @Produces(MediaType.APPLICATION_YAML)
  public String getSwaggerYmlFile() throws IOException {
    Optional<URL> resource = loader.getResource("classpath:META-INF/swagger/swagger.yml");
    return IOUtils.toString(
        (BufferedInputStream) resource.orElseThrow().getContent(), StandardCharsets.UTF_8);
  }
}```