Why API docs matter in Spring Boot - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a simple REST controller in Spring Boot.

Spring Boot

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.GetMapping;

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return [1];
    }
}

Drag options to blanks, or click blank then click option'

ASystem.out.println("Hello, World!")

B"Hello, World!"

Creturn "Hello, World!";

DHello, World!

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string

Using print statements instead of return

The method should return a string literal with quotes to send as the HTTP response body.

2fill in blank

medium

Complete the code to add OpenAPI documentation annotation for the controller method.

Spring Boot

import io.swagger.v3.oas.annotations.Operation;

@RestController
public class HelloController {
    @GetMapping("/hello")
    @Operation(summary = [1])
    public String sayHello() {
        return "Hello, World!";
    }
}

Drag options to blanks, or click blank then click option'

A"Greeting endpoint"

BReturns a greeting message

C"Hello endpoint"

D"Returns a greeting message"

Attempts:

3 left

💡 Hint

Common Mistakes

Missing quotes around the summary

Using plain text without quotes

The summary attribute requires a string literal describing the API operation.

3fill in blank

hard

Fix the error in the code to correctly document the response code in OpenAPI annotation.

Spring Boot

import io.swagger.v3.oas.annotations.responses.ApiResponse;

@RestController
public class HelloController {
    @GetMapping("/hello")
    @ApiResponse(responseCode = [1], description = "Successful greeting")
    public String sayHello() {
        return "Hello, World!";
    }
}

Drag options to blanks, or click blank then click option'

A200

BHttpStatus.OK

C"200"

DOK

Attempts:

3 left

💡 Hint

Common Mistakes

Using integer 200 without quotes

Using enum constants instead of string

The responseCode attribute expects a string literal representing the HTTP status code.

4fill in blank

hard

Fill both blanks to create a Map of endpoint names to their descriptions for API documentation.

Spring Boot

Map<String, String> apiDocs = Map.of(
    [1], [2]
);

Drag options to blanks, or click blank then click option'

A"/hello"

B"Returns greeting message"

C"/goodbye"

D"Returns farewell message"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping key and value

Missing quotes around strings

The Map.of method takes key-value pairs as arguments. The key is the endpoint path, and the value is its description.

5fill in blank

hard

Fill all three blanks to define a Spring Boot REST controller with OpenAPI tags and summary.

Spring Boot

import io.swagger.v3.oas.annotations.tags.Tag;
import io.swagger.v3.oas.annotations.Operation;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.GetMapping;

@RestController
@Tag(name = [1], description = [2])
public class GreetingController {
    @GetMapping("/greet")
    @Operation(summary = [3])
    public String greet() {
        return "Greetings!";
    }
}

Drag options to blanks, or click blank then click option'

A"Greeting API"

B"API for greeting endpoints"

C"Returns a greeting message"

D"GreetingController"

Attempts:

3 left

💡 Hint

Common Mistakes

Using class names instead of descriptive strings

Missing quotes around strings

The @Tag annotation needs a name and description as string literals. The @Operation summary is also a string literal describing the method.

Practice

1. Why are API documentation tools important in Spring Boot projects?

easy

A. They replace the need for writing any code.

B. They automatically generate clear docs for backend services.

C. They slow down the application performance.

D. They only work with frontend frameworks.

Solution

1. Step 1: Understand the role of API docs

   API docs explain how backend services work and how to use them.

2. Step 2: Recognize automation benefits in Spring Boot

   Tools like Springdoc generate these docs automatically, saving time and reducing errors.

3. Final Answer:

   They automatically generate clear docs for backend services. -> Option B

4. Quick Check:

   API docs help by auto-generating clear service info [OK]

Hint: API docs = clear backend usage + automation [OK]

Common Mistakes:

• Thinking API docs replace coding
• Believing docs slow app performance
• Assuming docs only help frontend

2. Which annotation is commonly used in Spring Boot to enable automatic API documentation generation?

easy

A. @EnableSwagger2

B. @SpringBootApplication

C. @RestController

D. @DocumentedApi

Solution

1. Step 1: Identify the annotation for Swagger integration

   @EnableSwagger2 is used to enable Swagger-based API docs generation in Spring Boot.

2. Step 2: Differentiate from other annotations

   @SpringBootApplication starts the app, @RestController defines controllers, and @DocumentedApi is not a valid Spring Boot annotation.

3. Final Answer:

   @EnableSwagger2 -> Option A

4. Quick Check:

   Swagger docs enabled by @EnableSwagger2 [OK]

Hint: Swagger docs need @EnableSwagger2 annotation [OK]

Common Mistakes:

• Confusing @SpringBootApplication with docs enabling
• Using @RestController for docs generation
• Assuming @DocumentedApi is a real annotation

3. Given this Spring Boot controller snippet with Springdoc enabled, what will the generated API docs show for the endpoint?

@RestController
@RequestMapping("/api")
public class UserController {
  @GetMapping("/users/{id}")
  public User getUser(@PathVariable String id) {
    return new User(id, "Alice");
  }
}

medium

A. An endpoint POST /api/users that creates a new user.

B. An endpoint GET /users without path variables.

C. No endpoint will be documented because @GetMapping is missing.

D. An endpoint GET /api/users/{id} that returns a User object with id and name.

Solution

1. Step 1: Analyze the controller mapping

   The class maps to /api, and the method maps GET requests to /users/{id} with a path variable.

2. Step 2: Understand Springdoc output

   Springdoc generates docs showing GET /api/users/{id} returning a User object with id and name fields.

3. Final Answer:

   An endpoint GET /api/users/{id} that returns a User object with id and name. -> Option D

4. Quick Check:

   GET /api/users/{id} documented with User return [OK]

Hint: Check @RequestMapping + @GetMapping paths for docs URL [OK]

Common Mistakes:

• Confusing GET with POST method
• Ignoring path variables in URL
• Assuming no docs generated without extra config

4. You added Springdoc to your Spring Boot app but the API docs page shows no endpoints. What is the most likely cause?

medium

A. You forgot to add @RestController to your controller classes.

B. You wrote your endpoints in XML configuration.

C. You used @Controller instead of @RestController without @ResponseBody.

D. You did not start the Spring Boot application.

Solution

1. Step 1: Understand Springdoc endpoint detection

   Springdoc detects REST endpoints typically annotated with @RestController or @Controller + @ResponseBody.

2. Step 2: Identify missing @ResponseBody effect

   If you use @Controller without @ResponseBody, Springdoc may not detect endpoints as REST APIs, so docs show empty.

3. Final Answer:

   You used @Controller instead of @RestController without @ResponseBody. -> Option C

4. Quick Check:

   Missing @ResponseBody means no REST endpoints detected [OK]

Hint: Use @RestController or @Controller + @ResponseBody for docs [OK]

Common Mistakes:

• Assuming @Controller alone is enough for REST docs
• Forgetting to run the app before checking docs
• Thinking XML config affects Springdoc detection

5. How can API documentation improve teamwork and maintenance in a Spring Boot project?

hard

A. By providing clear, up-to-date info on endpoints, it helps teammates understand and use APIs correctly.

B. By hiding internal API details to prevent misuse.

C. By automatically fixing bugs in the code.

D. By replacing the need for writing unit tests.

Solution

1. Step 1: Identify the role of API docs in teamwork

   Clear API docs explain how endpoints work, so teammates can use and build on them without confusion.

2. Step 2: Understand maintenance benefits

   Up-to-date docs reduce errors and speed up onboarding, making maintenance easier and safer.

3. Final Answer:

   By providing clear, up-to-date info on endpoints, it helps teammates understand and use APIs correctly. -> Option A

4. Quick Check:

   Clear docs improve teamwork and maintenance [OK]

Hint: Good docs = better teamwork + easier maintenance [OK]

Common Mistakes:

• Thinking docs hide API details
• Believing docs fix bugs automatically
• Assuming docs replace testing