API documentation is a crucial part of any software project, as it helps developers understand how to use the API and enables them to build robust and reliable integrations. In this blog post, we will explore how to integrate Java Spring REST Docs with OpenAPI to generate comprehensive and easy-to-read API documentation.

Java Spring REST Docs

Java Spring REST Docs is a powerful framework for documenting RESTful APIs in Spring Boot applications. It generates API documentation based on test cases, making it easy to keep the documentation up-to-date with the actual behavior of the API.

OpenAPI

OpenAPI, formerly known as Swagger, is a specification for defining APIs in a machine-readable format. It provides a standardized way to describe API endpoints, request/response payloads, and various other details required for API documentation.

Integrating Java Spring REST Docs with OpenAPI

To integrate Java Spring REST Docs with OpenAPI, we can make use of the Spring Fox library. Spring Fox provides an integration layer between Java Spring REST Docs and OpenAPI, allowing us to generate documentation in OpenAPI format.

Here are the steps to integrate Java Spring REST Docs with OpenAPI:

1. Add the necessary dependencies to your project’s pom.xml or build.gradle file:

<dependency>
    <groupId>org.springframework.restdocs</groupId>
    <artifactId>spring-restdocs-mockmvc</artifactId>
    <version>2.0.5.RELEASE</version>
    <scope>test</scope>
</dependency>

<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-boot-starter</artifactId>
    <version>3.0.0</version>
</dependency>

1. Write test cases for your API using Java Spring REST Docs. These test cases will serve as the input for generating the API documentation.

2. Configure Java Spring REST Docs to generate the documentation in OpenAPI format. This can be done by adding the following configuration to your test class:

@BeforeEach
public void setUp() {
    RestAssuredRestDocumentation.documentationConfiguration(restDocumentation)
      .snippets().withDefaults(
        openapi3RequestBody(),
        openapi3RequestHeaders(),
        openapi3ResponseFields()
      );
}

1. Generate the OpenAPI documentation by running the test cases. Java Spring REST Docs will generate snippets of the API documentation.

2. Finally, use the Spring Fox library to aggregate the snippets and generate the final OpenAPI documentation. This can be done using the following code:

@RunWith(SpringRestDocsRestDocumentationRunner.class)
@AutoConfigureRestDocs(outputDir = "target/snippets")
public class ApiDocumentation {

    @Autowired
    private WebApplicationContext webApplicationContext;

    @Test
    public void testApiDocumentation() throws Exception {
        // Perform API requests and capture snippets
        mockMvc.perform(get("/api/endpoint"))
                .andExpect(status().isOk())
                .andDo(document("api-endpoint",
                        preprocessRequest(prettyPrint()),
                        preprocessResponse(prettyPrint()),
                        // Additional snippets can be added here
                ));

        // Generate OpenAPI documentation
        Swagger2MarkupConverter.from(outputDirectory)
                .build()
                .toFile(Paths.get("target/generated/openapi.yaml"));
    }
}

By following these steps, you can easily integrate Java Spring REST Docs with OpenAPI and generate comprehensive API documentation. This approach ensures that the documentation stays up-to-date with the actual behavior of the API, making it a valuable resource for developers integrating with your API.

#api #documentation