Generating client code from spec in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to generate a Spring Boot client from an OpenAPI spec using the CLI.

Spring Boot

openapi-generator-cli generate -i api.yaml -g [1] -o ./client

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

Apython

Bjava

Cspring

Dhtml

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'java' instead of 'spring' generates a plain Java client, not Spring Boot.

Using unrelated generators like 'python' or 'html' will not create a Spring Boot client.

The spring generator creates a Spring Boot client from the OpenAPI spec.

2fill in blank

medium

Complete the code to add a library option for the Spring client generation.

Spring Boot

openapi-generator-cli generate -i api.yaml -g spring --library [1] -o ./client

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

Afeign

Bokhttp

Cresttemplate

Dretrofit

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'resttemplate' when the task expects Feign usage.

Using 'okhttp' or 'retrofit' which are not typical Spring Boot client libraries.

The feign library option generates a Spring client using Feign for declarative REST calls.

3fill in blank

hard

Fix the error in the command to generate a Spring client with the correct package name.

Spring Boot

openapi-generator-cli generate -i api.yaml -g spring --package-name [1] -o ./client

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

Acom.example client

Bcom-example-client

Ccom_example_client

Dcom.example.client

Attempts:

3 left

💡 Hint

Common Mistakes

Using dashes or spaces in package names causes errors.

Underscores are not standard in Java package names.

Package names in Java must use dot notation without spaces or dashes, like com.example.client.

4fill in blank

hard

Fill both blanks to configure the generator to use a specific API and model package.

Spring Boot

openapi-generator-cli generate -i api.yaml -g spring --api-package [1] --model-package [2] -o ./client

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

Acom.example.api

Bcom.example.model

Ccom.example.service

Dcom.example.data

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up API and model package names.

Using unrelated package names that don't reflect API or model.

The --api-package sets the package for API interfaces, and --model-package sets the package for data models.

5fill in blank

hard

Fill all three blanks to generate a Spring client with a custom group ID, artifact ID, and version.

Spring Boot

openapi-generator-cli generate -i api.yaml -g spring --group-id [1] --artifact-id [2] --artifact-version [3] -o ./client

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

Acom.example

Bmy-client

C1.0.0

Dorg.sample

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid version formats.

Confusing group ID and artifact ID values.

The --group-id, --artifact-id, and --artifact-version define Maven coordinates for the generated client.

Practice

1. What is the main benefit of generating client code from an API specification in Spring Boot projects?

easy

A. It automatically deploys the API to the cloud.

B. It saves time and reduces errors when calling APIs.

C. It replaces the need for a backend server.

D. It creates database schemas from the API.

Solution

1. Step 1: Understand the purpose of client code generation

   Generating client code means creating ready-to-use code to call APIs, which saves manual coding effort.

2. Step 2: Identify the main benefit in Spring Boot context

   This process reduces human errors and speeds up development by automating client creation.

3. Final Answer:

   It saves time and reduces errors when calling APIs. -> Option B

4. Quick Check:

   Client code generation = saves time and reduces errors [OK]

Hint: Remember: generated client code automates API calls [OK]

Common Mistakes:

• Thinking it deploys APIs automatically
• Confusing client code with backend code
• Assuming it creates database schemas

2. Which command correctly generates Spring client code using openapi-generator-cli from a spec file named api.yaml?

easy

A. openapi-generator-cli generate -i api.yaml -g spring -o ./client

B. openapi-generator-cli create -i api.yaml -g springboot -o ./client

C. openapi-generator-cli generate -i api.yaml -g java -o ./client

D. openapi-generator-cli build -i api.yaml -g spring -o ./client

Solution

1. Step 1: Identify the correct command syntax for code generation

   The command uses 'generate' to create code, '-i' for input spec, '-g' for generator type, and '-o' for output folder.

2. Step 2: Match the correct generator for Spring client code

   The generator name for Spring client code is 'spring', not 'springboot' or 'java'.

3. Final Answer:

   openapi-generator-cli generate -i api.yaml -g spring -o ./client -> Option A

4. Quick Check:

   Correct command = generate + -g spring [OK]

Hint: Use 'generate' and '-g spring' for Spring client code [OK]

Common Mistakes:

• Using 'create' or 'build' instead of 'generate'
• Using wrong generator name like 'springboot'
• Using '-g java' which is for Java server, not Spring client

3. Given the command openapi-generator-cli generate -i petstore.yaml -g spring -o ./client, what will be the main output?

medium

A. A Spring Boot server application implementing the API

B. A database migration script

C. A JavaScript client library for the API

D. A Spring client library to call the API endpoints

Solution

1. Step 1: Analyze the generator option '-g spring'

   The 'spring' generator creates Spring client code, not server code or JavaScript libraries.

2. Step 2: Understand the output folder './client'

   The generated code will be placed in './client' as a client library to call API endpoints.

3. Final Answer:

   A Spring client library to call the API endpoints -> Option D

4. Quick Check:

   Generator 'spring' = Spring client library [OK]

Hint: '-g spring' generates client code, not server or JS [OK]

Common Mistakes:

• Confusing client code with server implementation
• Expecting JavaScript code from Spring generator
• Thinking it creates database scripts

4. You ran openapi-generator-cli generate -i api.yaml -g springboot -o ./client but got an error: Unknown generator: springboot. What is the likely cause?

medium

A. You need to install Java separately.

B. The input file 'api.yaml' is missing.

C. You used the wrong generator name 'springboot' instead of 'spring'.

D. The output folder './client' already exists.

Solution

1. Step 1: Check the error message details

   The error says 'Unknown generator: springboot', indicating the generator name is invalid.

2. Step 2: Verify correct generator name for Spring client

   The correct generator is 'spring', not 'springboot'. Using 'springboot' causes this error.

3. Final Answer:

   You used the wrong generator name 'springboot' instead of 'spring'. -> Option C

4. Quick Check:

   Error 'Unknown generator' = wrong generator name [OK]

Hint: Check generator name spelling carefully [OK]

Common Mistakes:

• Typing 'springboot' instead of 'spring'
• Ignoring error details
• Assuming missing input file causes this error

5. You want to generate a Spring client from an OpenAPI spec but only want to include APIs tagged with 'user'. Which approach should you take?

hard

A. Modify the OpenAPI spec to only include 'user' tagged APIs before generation.

B. Manually delete unwanted APIs from the generated code after generation.

C. Use --ignore-file-override to exclude APIs by tag.

D. Use the --global-property apis=user option with openapi-generator-cli.

Solution

1. Step 1: Understand filtering options in openapi-generator-cli

   The CLI does not support filtering APIs by tag directly during generation.

2. Step 2: Consider practical ways to generate only 'user' APIs

   Modifying the OpenAPI spec to include only desired tags is the cleanest and recommended approach.

3. Final Answer:

   Modify the OpenAPI spec to only include 'user' tagged APIs before generation. -> Option A

4. Quick Check:

   Filter APIs by editing spec before generation [OK]

Hint: Filter APIs by editing spec before generating client [OK]

Common Mistakes:

• Expecting CLI to filter APIs by tag automatically
• Deleting code manually after generation (error-prone)
• Using unsupported CLI options for filtering