OpenAPI Generator for the spring-boot-feign library

Overview

This is a boiler-plate project to generate your own project derived from an OpenAPI specification. Its goal is to get you started with the basic plumbing so you can put in your own logic. It won't work without your changes applied.

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?

At this point, you've likely generated a client setup. It will include something along these lines:

.
|- README.md    // this file
|- pom.xml      // build script
|-- src
|--- main
|---- java
|----- com.my.company.codegen.MyCodegenGenerator.java // generator file
|---- resources
|----- my-codegen // template files
|----- META-INF
|------ services
|------- org.openapitools.codegen.CodegenConfig

You will need to make changes in at least the following:

MyCodegenGenerator.java

Templates in this folder:

src/main/resources/my-codegen

Once modified, you can run this:

mvn package

In your generator project. A single jar file will be produced in target. You can now use that with OpenAPI Generator:

For mac/linux:

java -cp /path/to/openapi-generator-cli.jar:/path/to/your.jar org.openapitools.codegen.OpenAPIGenerator generate -g my-codegen -i /path/to/openapi.yaml -o ./test

(Do not forget to replace the values /path/to/openapi-generator-cli.jar, /path/to/your.jar and /path/to/openapi.yaml in the previous command)

For Windows users, you will need to use ; instead of : in the classpath, e.g.

java -cp /path/to/openapi-generator-cli.jar;/path/to/your.jar org.openapitools.codegen.OpenAPIGenerator generate -g my-codegen -i /path/to/openapi.yaml -o ./test

Now your templates are available to the client generator and you can write output values

But how do I modify this?

The MyCodegenGenerator.java has comments in it--lots of comments. There is no good substitute for reading the code more, though. See how the MyCodegenGenerator implements CodegenConfig. That class has the signature of all values that can be overridden.

You can also step through MyCodegenGenerator.java in a debugger. Just debug the JUnit test in DebugCodegenLauncher. That runs the command line tool and lets you inspect what the code is doing.

For the templates themselves, you have a number of values available to you for generation. You can execute the java command from above while passing different debug flags to show the object you have available during client generation:

# The following additional debug options are available for all codegen targets:
# -DdebugOpenAPI prints the OpenAPI Specification as interpreted by the codegen
# -DdebugModels prints models passed to the template engine
# -DdebugOperations prints operations passed to the template engine
# -DdebugSupportingFiles prints additional data passed to the template engine

java -DdebugOperations -cp /path/to/openapi-generator-cli.jar:/path/to/your.jar org.openapitools.codegen.OpenAPIGenerator generate -g my-codegen -i /path/to/openapi.yaml -o ./test

Will, for example, output the debug info for operations. You can use this info in the api.mustache file.