OpenAPI Generator for Java with support for nested allOf-types and multiple inheritance with oneOf

This generates creates Java classes without framework-specified annotations for implementing and using OpenAPI APIs in Java. It supports many of the more advanced features of the OpenAPI spec

Features

• Generates POJOs without reliance on framework specified annotations
• Models are generated with convenient methods for checking missing required fields and read-only fields with values and to copy between objects
• Implements type polymorphism with oneOf-types, even supporting multiple inheritance for classes that are included in multiple oneOf-types
• Implements inheritance with allOf-types, including multiple levels of inheritance
• Generates client code using HttpURLConnection for HTTP and JSONB for JSON deserialization
• Supports optional, repeated and binary request parameters
• Generates SampleData which can provide randomized model data, accepting a seed to generate the same data every time

What's OpenAPI

The goal of OpenAPI is to define a standard, language-agnostic interface to REST APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection. When properly described with OpenAPI, a consumer can understand and interact with the remote service with a minimal amount of implementation logic. Similar to what interfaces have done for lower-level programming, OpenAPI removes the guesswork in calling the service.

Check out OpenAPI-Spec for additional information about the OpenAPI project, including additional libraries with support for other languages and more.

How do I use this?

Add to your pom.xml:

    <build>
        <plugins>
            <plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <version>7.5.0</version>
                <executions>
                    <execution>
                        <id>petstore-java</id>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>${project.basedir}/src/main/openapi-spec/openapi.yaml</inputSpec>
                            <generatorName>java-annotationfree</generatorName>
                            <modelNameSuffix>Dto</modelNameSuffix>
                            <output>target/generated-sources/openapi-java</output>
                            <configOptions>
                                <generateModelTests>true</generateModelTests>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
                <dependencies>
                    <dependency>
                        <groupId>io.github.jhannes.openapi</groupId>
                        <artifactId>openapi-generator-java-annotationfree</artifactId>
                        <version>0.6.0</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>

Sample output

Petstore model

Polymorphism

components:
  schemas:
    CreationError:
      oneOf:
        - $ref: '#/components/schemas/GeneralError'
        - $ref: '#/components/schemas/DuplicateIdentifierError'
        - $ref: '#/components/schemas/IllegalEmailAddressError'
      discriminator:
        propertyName: code
    UpdateError:
      oneOf:
        - $ref: '#/components/schemas/GeneralError'
        - $ref: '#/components/schemas/NotFoundError'
        - $ref: '#/components/schemas/DuplicateIdentifierError'
        - $ref: '#/components/schemas/IllegalEmailAddressError'
      discriminator:
        propertyName: code
    GeneralError:
      properties:
        code:
          type: string
        description:
          type: string
      required:
        - code
        - description

public interface CreationErrorDto  {
    String getCode();

    static GeneralErrorDto GeneralError() {
        GeneralErrorDto result = new GeneralErrorDto();
        result.code("GeneralError");
        return result;
    }

    static Class<? extends CreationErrorDto> getType(String type) {
        switch (type) {
        case "GeneralError":
            return GeneralErrorDto.class;
        default:
            throw new IllegalArgumentException("Illegal code " + type);
        }
    }

    void readOnlyFieldsWithValue(List<String> fields);
}

public class GeneralErrorDto implements CreationErrorDto, UpdateErrorDto {

    private String code;

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public GeneralErrorDto code(String code) {
        this.code = code;
        return this;
    }
}

Contribution

Pull requests are welcome. In order to safely support changes, the project comes with a large set of OpenAPI specs for which snapshot tests are generated. If a change produces different output for one of the included specs the tests fail until the snapshots are updated.

For an effective development process, see FocusedExampleTest