java-micronaut-server And generateControllerAsAbstract=true Results in "class not found" Errors

java-micronaut-server And generateControllerAsAbstract=true Results in "class not found" Errors

I opted to not create a [BUG] issue, since the java-micronaut-server is still listed as a Beta version.

While working on a short article that leverages and OpenAPI specification to build services, I was able to successfully use Spring Boot and Quarkus. The final article of my series focused on Micronaut and I was excited to see that an OpenAPI generator exists for this framework.

By default, the 7.12.0 version of the generator ends up creating a DefaultController which is a class. I eventually discovered the generateControllerAsAbstract=true configuration option which did introduce the AbstractDefaultController however, with this change in place I started seeing "class not found" errors. What surprised me is that errors pointed to HttpStatusException and HttpStatus - both of which were in the class path and available in my local IntelliJ instance. If I were to switch back to generateControllerAsAbstract=false, the errors went away.

I also noticed that if I provided my own api, model and invoker packages, the AbstractDefaultController appeared to ignore these settings and created the class in the org.openapitools package.

Here is my build.gradle file:

plugins {
    id("io.micronaut.application") version "4.5.0"
    id("com.gradleup.shadow") version "8.3.6"
    id("io.micronaut.aot") version "4.5.0"
    id("org.openapi.generator") version '7.12.0'
}

openApiGenerate {
    generatorName = "java-micronaut-server"
    inputSpec = "$rootDir/src/main/resources/openapi.yaml"
    outputDir = "$buildDir/generated"
    //apiPackage = "quotes.micronaut.openapi.api"
    //modelPackage = "quotes.micronaut.openapi.model"
    //invokerPackage = "quotes.micronaut.openapi.invoker"
    configOptions = [
            dateLibrary: "java8",
            useJakartaEe: "true",
            useBeanValidation: "false",
            reactive: "false",
            generateControllerAsAbstract: "true",
    ]
}

version = "0.1"
group = "quotes.micronaut"

repositories {
    mavenCentral()
}

dependencies {
    annotationProcessor("io.micronaut:micronaut-http-validation")
    annotationProcessor("io.micronaut:micronaut-inject-java")
    annotationProcessor("io.micronaut.openapi:micronaut-openapi")
    annotationProcessor("io.micronaut.serde:micronaut-serde-processor")
    annotationProcessor("io.micronaut.validation:micronaut-validation-processor")
    annotationProcessor("org.projectlombok:lombok")

    implementation("io.micronaut:micronaut-http")
    implementation("io.micronaut.security:micronaut-security-annotations")
    implementation("io.micronaut.security:micronaut-security")
    implementation("io.micronaut.serde:micronaut-serde-jackson")
    implementation("io.micronaut.validation:micronaut-validation")

    compileOnly("io.micronaut:micronaut-http-server")
    compileOnly("io.micronaut.openapi:micronaut-openapi-annotations")
    compileOnly("org.projectlombok:lombok")

    runtimeOnly("ch.qos.logback:logback-classic")

    testImplementation("io.micronaut:micronaut-http-client")
}


application {
    mainClass = "quotes.micronaut.Application"
}
java {
    sourceCompatibility = JavaVersion.toVersion("17")
    targetCompatibility = JavaVersion.toVersion("17")
}

sourceSets {
    main {
        java {
            srcDirs += "$buildDir/generated/src/main/java"
        }
    }
}

compileJava.dependsOn tasks.openApiGenerate
graalvmNative.toolchainDetection = false

micronaut {
    runtime("netty")
    testRuntime("junit5")
    processing {
        incremental(true)
        annotations("quotes.micronaut.*")
    }
    aot {
        // Please review carefully the optimizations enabled below
        // Check https://micronaut-projects.github.io/micronaut-aot/latest/guide/ for more details
        optimizeServiceLoading = false
        convertYamlToJava = false
        precomputeOperations = true
        cacheEnvironment = true
        optimizeClassLoading = true
        deduceEnvironment = true
        optimizeNetty = true
        replaceLogbackXml = true
    }
}

If interested, here's the OpenAPI Specification that I have been using for my articles:

openapi: 3.0.0
info:
  title: Motivational Quotes API
  description: An API that provides motivational quotes.
  version: 1.0.0
servers:
  - url: https://api.example.com
    description: Production server
paths:
  /quotes:
    get:
      summary: Get all motivational quotes
      operationId: getAllQuotes
      responses:
        '200':
          description: A list of motivational quotes
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Quote'
  /quotes/random:
    get:
      summary: Get a random motivational quote
      operationId: getRandomQuote
      responses:
        '200':
          description: A random motivational quote
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Quote'
  /quotes/{id}:
    get:
      summary: Get a motivational quote by ID
      operationId: getQuoteById
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: integer
      responses:
        '200':
          description: A motivational quote
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Quote'
        '404':
          description: Quote not found
components:
  schemas:
    Quote:
      type: object
      required:
        - id
        - quote
      properties:
        id:
          type: integer
        quote:
          type: string

I opted to go a different direction for the article, but I wanted to log this ticket, in case it provides value for someone else in the future.

Have a really great day!

Start by reproducing the issue with the provided build.gradle configuration, the java-micronaut-server generator, and the supplied openapi.yaml. Inspect the generated AbstractDefaultController and its package imports, then verify compilation with generateControllerAsAbstract=true and custom api, model, and invoker packages. Done means generation no longer produces class-not-found errors and respects those package settings.