OpenAPI Annotation Processor

Experimental compile-time OpenAPI integration for Javalin 5.x ecosystem. This is a new plugin that replaces old built-in OpenApi module, the API looks quite the same despite of some minor changes.

Setup

Download required dependencies:

Gradle setup for Javalin 5.x

repositories {
    maven { url 'https://maven.reposilite.com/releases' }
    // For snapshots
    maven { url 'https://maven.reposilite.com/snapshots' }
}

dependencies {
    def openapi = "5.0.0-SNAPSHOT"
    
    // For Java projects
    annotationProcessor("io.javalin:openapi-annotation-processor:$openapi")
    // For Kotlin projects
    kapt("io.javalin:openapi-annotation-processor:$openapi")

    implementation("io.javalin:javalin-openapi-plugin:$openapi") // for /openapi route with JSON scheme
    implementation("io.javalin:javalin-swagger-plugin:$openapi") // for Swagger UI
    implementation("io.javalin:javalin-redoc-plugin:$openapi") // for ReDoc UI
}

Maven setup for Javalin 5.x

<project>
    <repositories>
        <!--Releases-->
        <repository>
            <id>reposilite-repository</id>
            <url>https://maven.reposilite.com/releases</url>
        </repository>
        <!-- Snapshots -->
        <repository>
            <id>reposilite-repository</id>
            <url>https://maven.reposilite.com/snapshots</url>
        </repository>
    </repositories>
    
    <dependencies>
        <!-- OpenApi plugin -->
        <dependency>
            <groupId>io.javalin</groupId>
            <artifactId>javalin-openapi-plugin</artifactId>
            <version>${javalin.version}</version>
        </dependency>
        <!-- Swagger plugin -->
        <dependency>
            <groupId>io.javalin</groupId>
            <artifactId>javalin-swagger-plugin</artifactId>
            <version>${javalin.version}</version>
        </dependency>
        <!-- ReDoc plugin -->
        <dependency>
            <groupId>io.javalin</groupId>
            <artifactId>javalin-redoc-plugin</artifactId>
            <version>${javalin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.webjars.npm</groupId>
            <artifactId>redoc</artifactId>
            <version>2.0.0-rc.56</version>
            <exclusions>
                <exclusion>
                    <groupId>*</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>
    
    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.10.1</version>
                    <configuration>
                        <annotationProcessorPaths>
                            <annotationProcessorPath>
                                <groupId>io.javalin</groupId>
                                <artifactId>openapi-annotation-processor</artifactId>
                                <version>${javalin.version}</version>
                            </annotationProcessorPath>
                        </annotationProcessorPaths>
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

And enable OpenAPI plugin for Javalin with Swagger UI:

Javalin.create(config -> {
    String deprecatedDocsPath = "/swagger-docs";
    
    OpenApiConfiguration openApiConfiguration = new OpenApiConfiguration();
    openApiConfiguration.setTitle("AwesomeApp");
    openApiConfiguration.setDocumentationPath(deprecatedDocsPath); // by default it's /openapi
    config.registerPlugin(new OpenApiPlugin(openApiConfiguration));
    
    SwaggerConfiguration swaggerConfiguration = new SwaggerConfiguration();
    swaggerConfiguration.setDocumentationPath(deprecatedDocsPath);
    config.registerPlugin(new SwaggerPlugin(swaggerConfiguration));
    
    ReDocConfiguration reDocConfiguration = new ReDocConfiguration();
    reDocConfiguration.setDocumentationPath(deprecatedDocsPath);
    config.registerPlugin(new ReDocPlugin(reDocConfiguration));
})
.start(8080);

This plugin is also compatibile with Javalin 4.x, see: Javalin RFC - OpenApi plugin

Notes

• Reflection free, does not perform any extra operations at runtime
• Uses @OpenApi to simplify migration from bundled OpenApi implementation
• Supports Java 8+ (also 16 and any further releases) and Kotlin (through Kapt)
• Uses internal WebJar handler that works with /* route out of the box
• Provides better projection of OpenAPI specification
• Schema validation through Swagger core module

Other examples

• Reposilite - real world app using Javalin and OpenApi integration
• Javalin OpenApi Example by paulkagiri

Repository structure

• openapi-annotation-processor - compile-time annotation processor, should generate openapi.json resource or just a class
• openapi-annotations - annotations used by annotation processor to generate OpenAPI docs
• openapi-test - example Javalin application that uses OpenApi plugin in Gradle & Maven

Javalin:

• javalin-openapi-plugin - loads openapi.json resource and serves OpenApi endpoint
• javalin-swagger-plugin - serves Swagger UI
• javalin-redoc-plugin - serves ReDoc UI