OpenAPI

An OpenAPI Specification (OAS) is a description format for REST APIs. Swagger is a set of tools based on this specification for writing, documenting, and consuming REST APIs. For more information, refer to Swagger documentation.

CLion provides coding assistance for OpenAPI definitions in YAML and JSON files, and integration with Swagger Codegen for generating server stubs, client libraries (SDKs), and documentation based on your OpenAPI specification.

Create an OpenAPI specification

CLion recognizes a dedicated OpenAPI Specification file type with relevant coding assistance. These are regular YAML or JSON files with the definition of the OpenAPI specification version.

Create an OpenAPI Specification manually

In Project view, select New | OpenAPI Specification from the context menu.
Specify a name for the file and select the specification version and file format.

Depending on the format and version, the new OpenAPI specification file contains the following template:

openapi: 3.0.0
info:
    title: Title
    description: Title
    version: 1.0.0
servers:
    - url: 'https'
paths:

{
    "openapi": "3.0.0",
    "info": {
        "title": "Title",
        "description": "Title",
        "version": "1.0.0"
    },
    "servers": [
        {
            "url": "https"
        }
    ],
    "paths": {

    }
}

swagger: "2.0"
info:
    title: Title
    description: Title
    version: 1.0.0
host: www
schemes:
    - https
paths:

{
    "swagger": "2.0",
    "info": {
        "title": "Title",
        "description": "Title",
        "version": "1.0.0"
    },
    "host": "www",
    "schemes": [
        "https"
    ],
    "paths": {

    }
}

If you start with an empty YAML or JSON file, you can type opnp or swag and press Tab to insert the corresponding live template.

Reference a definition from a separate file

With OpenAPI 3.0, you can reference a definition hosted on any location using the $ref keyword. CLion provides you with path completion, validation, and quick navigation. For completion, CLion understands the context of the current file and of external files, and suggests using pointers to relevant elements.

Enter the $ref keyword.
Start typing the path to the external definition.

You can press Control+B to quickly navigate to the file and element you refer to.

Preview an OpenAPI specification

You can preview an OpenAPI specification using the integrated Swagger UI or Redoc UI. When an OpenAPI specification file is opened in the editor, use and in the top-right corner to show or hide the preview.

To swtich between Swagger UI and Redoc UI, hover over the preview area and click .

Split editor and preview horizontally

By default, the editor and preview are split vertically (side by side), which is convenient for wide monitors. You can also split it horizontally, so that the preview is displayed in the lower part of the editor, which is more convenient for portrait displays.

In the top-right corner of the editor, click Editor and Preview to open the editor and preview pane horizontally.
The icon should change to .

Add a remote OpenAPI specification

Endpoint URLs that you define in OpenAPI specifications in your project are available for code completion. If you are writing client code for an external specification, there is no need to add it as a file to your project for auto-completing endpoint URLs. You can add a link to the relevant remote specification.

In the Settings dialog (Control+Alt+S), select Languages & Frameworks | OpenAPI Specifications.
Click in the Remote Specifications list and specify the URL of an OpenAPI specification file or find an OpenAPI specification on SwaggerHub.

Use to reload specifications that were modified.

To add private OpenAPI specifications, provide your API key.

To add OpenAPI specifications from a self-hosted SwaggerHub On-Premise instance, specify the URL of your instance.

Compare OpenAPI specifications

When there is a newer specification version, you probably want to compare it against the older version to make sure that they are compatible. One way is to look at the diff Control+D and compare lines that changed. However, not all changes are critical for compatibility. CLion can compare the structure of OpenAPI specifications and create a summary of changed paths, parameters, responses, and any other elements that may break the compatibility.

In the Project tool window, select two OpenAPI specification files, right-click them and select Compare OpenAPI Specifications.

This generates a Markdown file with a summary of modified specification elements. The file opens in the editor with a preview panel that makes it easy to navigate the changes. It shows the changes in the file that you selected second compared to the first one.

Generate code from an OpenAPI specification

When you have a valid OpenAPI specification open, CLion suggests generating code from it:

Generate code based on the OpenAPI specification

Click in the gutter and select Run 'openapi file'. CLion generates source code files in the specified location and shows a notification with options to open the files or import them into your project as a separate module.

Swagger Codegen run configuration

CLion creates a OpenAPI/Swagger Code Generator run configuration when you run code generation for the first time for a particular file. To modify the run configuration, open Run | Edit Configurations and select the necessary configuration, or click in the gutter and select Modify Run Configuration.

You can configure the following common options at the top of the OpenAPI/Swagger Code Generator run configuration:

Name

Specify a name for the run configuration to quickly identify it among others when editing or running.

Allow multiple instances

Allow running multiple instances of this run configuration in parallel.

By default, it is disabled, and when you start this configuration while another instance is still running, CLion suggests stopping the running instance and starting another one. This is helpful when a run configuration consumes a lot of resources and there is no good reason to run multiple instances.

Store as project file

Save the file with the run configuration settings to share it with other team members. The default location is .idea/runConfigurations. However, if you do not want to share the .idea directory, you can save the configuration to any other directory within the project.

By default, it is disabled, and CLion stores run configuration settings in .idea/workspace.xml.

General Settings

If some of the settings are hidden, click Modify options to show them.

Item	Description
Specification path	Path to the OpenAPI specification.
Output Directory	Path to the directory for the generated files.
Code Generator	Select a type of code generator.
Language	The target language of the generated code.
JRE	Java runtime to use for running Swagger Codegen
Custom templates path	Path to a directory with your Mustache templates.
Configure generator	Provide configuration parameters depending on the target language. For more information, refer to the swagger-codegen/README.md.

Last modified: 07 September 2023