SpringDoc OpenAPI setup in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is SpringDoc OpenAPI used for in a Spring Boot project?

SpringDoc OpenAPI automatically generates API documentation for your Spring Boot REST APIs, making it easy to visualize and test endpoints.

beginner

Which dependency do you add to a Spring Boot project to enable SpringDoc OpenAPI?

Add org.springdoc:springdoc-openapi-starter-webmvc-ui to your pom.xml or build.gradle to enable SpringDoc OpenAPI with Swagger UI.

beginner

How do you access the Swagger UI after setting up SpringDoc OpenAPI in your Spring Boot app?

Open your browser and go to http://localhost:8080/swagger-ui.html or http://localhost:8080/swagger-ui/index.html to see the interactive API docs.

intermediate

What is the purpose of the @OpenAPIDefinition annotation in SpringDoc?

It lets you customize the OpenAPI metadata like title, version, description, and contact info for your API documentation.

intermediate

How can you exclude certain endpoints from appearing in the SpringDoc OpenAPI documentation?

Use the @Hidden annotation on controllers or methods you want to hide from the generated API docs.

Which dependency is recommended for adding SpringDoc OpenAPI UI support in a Spring Boot project?

A org.springdoc:springdoc-openapi-starter-webmvc-ui

B org.springframework.boot:spring-boot-starter-web

C io.swagger:swagger-ui

D org.springframework:springdoc-ui

The correct dependency is org.springdoc:springdoc-openapi-starter-webmvc-ui which includes SpringDoc and Swagger UI integration.

After setting up SpringDoc, where can you view the generated API documentation?

A http://localhost:8080/api-docs

B http://localhost:8080/openapi

C http://localhost:8080/swagger-ui.html

D http://localhost:8080/docs

The Swagger UI is accessible by default at /swagger-ui.html or /swagger-ui/index.html.

Which annotation allows you to customize the API title and version in SpringDoc?

A @OpenAPIDefinition

B @ApiInfo

C @ApiOperation

D @ApiResponse

The @OpenAPIDefinition annotation is used to set metadata like title and version.

How do you hide a REST controller method from SpringDoc generated docs?

A Add @Ignore

B Add @Hidden

C Add @Exclude

D Add @Invisible

The @Hidden annotation hides controllers or methods from the OpenAPI documentation.

What is the main benefit of using SpringDoc OpenAPI in your Spring Boot project?

A It replaces the need for REST controllers.

B It improves database performance.

C It secures your API endpoints.

D It automatically generates and updates API documentation.

SpringDoc OpenAPI automatically generates and updates API docs based on your code.

Explain how to set up SpringDoc OpenAPI in a new Spring Boot project and how to access the API documentation.

Think about dependencies, running the app, and the URL to view docs.

Describe how to customize the API metadata and hide specific endpoints in SpringDoc OpenAPI.

Focus on annotations for customization and exclusion.

Practice

1. What is the main purpose of adding springdoc-openapi-starter-webmvc-ui dependency in a Spring Boot project?

easy

A. To configure logging for the application

B. To enable database connectivity

C. To automatically generate live API documentation for the application

D. To add security features to the application

Solution

1. Step 1: Understand the role of springdoc-openapi-starter-webmvc-ui

   This dependency integrates SpringDoc OpenAPI with Spring Boot to generate live API docs automatically.

2. Step 2: Identify the purpose of the dependency

   It provides a user interface and backend support to display API documentation without manual setup.

3. Final Answer:

   To automatically generate live API documentation for the application -> Option C

4. Quick Check:

   SpringDoc dependency = live API docs [OK]

Hint: SpringDoc dependency creates live API docs automatically [OK]

Common Mistakes:

• Confusing it with database or security dependencies
• Thinking it configures logging
• Assuming manual doc writing is still needed

2. Which of the following is the correct way to define a basic OpenAPI bean in a Spring Boot application to customize API info?

easy

A. @Bean public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().name("API").ver("1.0")); }

B. @Bean public OpenAPI customOpenAPI() { return new OpenAPI().setTitle("API").setVersion("1.0"); }

C. @Bean public OpenAPI customOpenAPI() { return new OpenAPI().info("API", "1.0"); }

D. @Bean public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("API").version("1.0")); }

Solution

1. Step 1: Recall the OpenAPI bean syntax

   The OpenAPI bean requires an Info object with title and version set via methods like title() and version().

2. Step 2: Compare options with correct method names

   Only @Bean public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("API").version("1.0")); } uses correct chaining: new OpenAPI().info(new Info().title("API").version("1.0"))

3. Final Answer:

   @Bean public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("API").version("1.0")); } -> Option D

4. Quick Check:

   OpenAPI bean uses info(new Info().title().version()) [OK]

Hint: Use Info().title() and .version() methods inside OpenAPI bean [OK]

Common Mistakes:

• Using incorrect method names like setTitle or info(String, String)
• Passing strings directly instead of Info object
• Using non-existent methods like name() or ver()

3. Given this Spring Boot configuration snippet, what will be the URL path to access the Swagger UI documentation?

@SpringBootApplication
public class DemoApplication {
  public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
  }
}

Assuming springdoc-openapi-starter-webmvc-ui is added as dependency and no custom properties are set.

medium

A. /swagger-ui.html

B. /swagger-ui/index.html

C. /api-docs

D. /openapi-ui

Solution

1. Step 1: Recall default Swagger UI path with SpringDoc

   SpringDoc by default serves Swagger UI at /swagger-ui/index.html

2. Step 2: Eliminate other options

   /swagger-ui.html is old Swagger path, /api-docs is for JSON docs, /openapi-ui is invalid default

3. Final Answer:

   /swagger-ui/index.html -> Option B

4. Quick Check:

   Default Swagger UI path = /swagger-ui/index.html [OK]

Hint: Swagger UI default path ends with /swagger-ui/index.html [OK]

Common Mistakes:

• Using old Swagger UI path /swagger-ui.html
• Confusing JSON docs path with UI path
• Assuming custom paths without configuration

4. You added the springdoc-openapi-starter-webmvc-ui dependency but when you run your Spring Boot app, the Swagger UI page shows a 404 error. What is the most likely cause?

medium

A. You are trying to access the Swagger UI at the wrong URL

B. You did not include the springdoc-openapi-starter-webmvc-ui dependency correctly

C. You have not defined an OpenAPI bean in your configuration

D. You forgot to add the @SpringBootApplication annotation

Solution

1. Step 1: Check common reasons for 404 on Swagger UI

   Missing dependency or wrong annotation usually cause app startup errors, not 404 on UI page.

2. Step 2: Verify URL correctness

   Swagger UI default URL is /swagger-ui/index.html, accessing other URLs like /swagger-ui.html causes 404.

3. Final Answer:

   You are trying to access the Swagger UI at the wrong URL -> Option A

4. Quick Check:

   404 on Swagger UI usually means wrong URL [OK]

Hint: Check Swagger UI URL carefully if 404 occurs [OK]

Common Mistakes:

• Assuming missing OpenAPI bean causes 404
• Thinking missing @SpringBootApplication causes 404 instead of startup failure
• Ignoring URL path correctness

5. You want to customize your Spring Boot API documentation with a title "My API" and version "2.0" using SpringDoc. Which code snippet correctly achieves this and ensures the OpenAPI bean is recognized by Spring?

hard

A. @Bean public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("My API").version("2.0")); }

B. @Component public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("My API").version("2.0")); }

C. public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("My API").version("2.0")); }

D. @Configuration public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("My API").version("2.0")); }

Solution

1. Step 1: Ensure the method is a Spring bean

   To register the OpenAPI object, the method must be annotated with @Bean inside a configuration class.

2. Step 2: Check the code snippet correctness

   @Bean public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("My API").version("2.0")); } correctly uses @Bean annotation and returns new OpenAPI().info(new Info().title("My API").version("2.0"))

3. Final Answer:

   @Bean public OpenAPI customOpenAPI() { return new OpenAPI().info(new Info().title("My API").version("2.0")); } -> Option A

4. Quick Check:

   Use @Bean annotation to register OpenAPI bean [OK]

Hint: Use @Bean annotation on method returning OpenAPI [OK]

Common Mistakes:

• Omitting @Bean annotation so Spring ignores the method
• Using @Component or @Configuration on method instead of class
• Not returning an OpenAPI object with info set