Generating client code from spec in Spring Boot - Step-by-Step Execution

Concept Flow - Generating client code from spec

Start with API Spec (OpenAPI)

↓

Use Code Generator Tool

↓

Generate Client Code

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Integrate Client Code in Spring Boot App

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Use Client to Call API

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Run & Test

The flow starts with an API specification, uses a tool to generate client code, integrates it into a Spring Boot app, then calls the API and tests.

Execution Sample

Spring Boot

openapi-generator-cli generate \
  -i api-spec.yaml \
  -g java \
  -o ./generated-client \
  --library resttemplate

This command generates Java client code from an OpenAPI spec using RestTemplate library.

Execution Table

Step	Action	Input	Output	Notes
1	Read API Spec	api-spec.yaml	Parsed API model	OpenAPI spec file is loaded and parsed
2	Select Generator	java + resttemplate	Generator config set	Choose Java client with RestTemplate support
3	Generate Code	Parsed API model + config	Java client code files	Client classes and models created in output folder
4	Integrate Code	Generated code	Spring Boot project updated	Add generated code as source or module
5	Use Client	Client classes	API calls from app	Call API endpoints via generated client methods
6	Run & Test	Spring Boot app	API responses	Verify client calls work as expected
7	Exit	N/A	N/A	Process complete, client code ready to use

💡 All steps completed, client code generated and integrated successfully

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 4	Final
apiSpec	null	Parsed API model	Parsed API model	Parsed API model	Parsed API model
generatorConfig	null	null	Set to Java + RestTemplate	Set to Java + RestTemplate	Set to Java + RestTemplate
generatedCode	null	null	Java client code files	Java client code files	Java client code files integrated
springBootApp	Existing app	Existing app	Existing app	App with client code	App with client code and API calls

Key Moments - 3 Insights

Why do we need an API spec file before generating client code?

The API spec file describes the API endpoints and data models. The generator uses it to create matching client code. See execution_table step 1.

What happens if we choose the wrong generator or library?

The generated code might not work with your Spring Boot app or chosen HTTP client. Step 2 shows selecting the correct generator is important.

How do we use the generated client code in our app?

After generation, you add the code to your project and call its methods to make API requests, as shown in steps 4 and 5.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output after Step 3?

A Spring Boot project updated

B Parsed API model

C Java client code files

D API responses

💡 Hint

Check the 'Output' column for Step 3 in the execution_table.

At which step is the client code integrated into the Spring Boot app?

A Step 4

B Step 2

C Step 3

D Step 5

💡 Hint

Look for 'Integrate Code' action in the execution_table.

If the API spec file is missing, which step will fail?

A Step 5

B Step 1

C Step 3

D Step 6

💡 Hint

Step 1 reads the API spec file; without it, parsing cannot happen.

Concept Snapshot

Generating client code from spec:
1. Start with an OpenAPI spec file describing the API.
2. Use a code generator tool (e.g., openapi-generator) with chosen language and library.
3. Generate client code files matching the API.
4. Add generated code to your Spring Boot app.
5. Use client methods to call API endpoints.
6. Run and test your app to verify calls work.

Full Transcript

This visual execution shows how to generate client code from an API specification in Spring Boot. First, the API spec file is read and parsed. Then, a code generator tool is configured to produce Java client code using RestTemplate. The generator creates client classes and models. Next, the generated code is integrated into the Spring Boot project. The app uses the client classes to call API endpoints. Finally, running the app tests the API calls. Key points include the importance of the API spec, choosing the right generator, and integrating the code properly.