SpringDoc OpenAPI setup in Spring Boot - Step-by-Step Execution

Concept Flow - SpringDoc OpenAPI setup

Add SpringDoc dependency

↓

Configure application.properties

↓

Create REST controller

↓

Run Spring Boot app

↓

Access /swagger-ui.html or /v3/api-docs

↓

View generated OpenAPI docs

This flow shows how to add SpringDoc to a Spring Boot app, configure it, run the app, and view the generated API docs.

Execution Sample

Spring Boot

dependencies {
  implementation 'org.springdoc:springdoc-openapi-starter-webmvc-ui:2.1.0'
}

@RestController
public class HelloController {
  @GetMapping("/hello")
  public String hello() { return "Hello"; }
}

This code adds SpringDoc dependency and creates a simple REST controller with one GET endpoint.

Execution Table

Step	Action	Result	Notes
1	Add SpringDoc dependency to build file	SpringDoc libraries available at runtime	Enables OpenAPI generation
2	Configure application.properties (optional)	Customize OpenAPI info or paths	Defaults work without config
3	Create REST controller with @GetMapping	Endpoint /hello available	Spring MVC registers handler
4	Run Spring Boot application	App starts with SpringDoc enabled	SpringDoc scans controllers
5	Access /v3/api-docs	JSON OpenAPI spec generated	Shows API structure
6	Access /swagger-ui/index.html	Interactive API docs UI shown	User can test endpoints
7	Exit	Setup complete and docs accessible	No errors

💡 All steps done, OpenAPI docs generated and UI accessible

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 4	Final
SpringDoc Dependency	Not present	Present	Present	Present	Present
REST Controller	None	None	Created	Created	Created
Application Running	No	No	No	Yes	Yes
OpenAPI Docs	None	None	None	Generated	Generated

Key Moments - 3 Insights

Why do we need to add the SpringDoc dependency first?

Without the dependency (see Step 1 in execution_table), SpringDoc classes and features are not available, so no OpenAPI docs can be generated.

What happens if we don't create any REST controllers?

If no controllers exist (Step 3), SpringDoc has no endpoints to scan, so the generated OpenAPI docs will be empty or minimal.

Why can we access /swagger-ui.html after running the app?

After the app runs with SpringDoc enabled (Step 4), it automatically provides the Swagger UI at /swagger-ui/index.html to interact with the API.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the OpenAPI JSON spec generated?

A Step 5

B Step 3

C Step 2

D Step 6

💡 Hint

Check the 'Result' column for when JSON OpenAPI spec is generated.

According to variable_tracker, when does the application start running?

A After Step 1

B After Step 3

C After Step 4

D After Step 5

💡 Hint

Look at 'Application Running' variable changes in variable_tracker.

If we remove the REST controller, how would the OpenAPI docs change?

A They would show all endpoints normally

B They would be empty or minimal

C The app would fail to start

D Swagger UI would not be available

💡 Hint

Refer to key_moments about missing controllers and OpenAPI docs content.

Concept Snapshot

SpringDoc OpenAPI setup:
1. Add SpringDoc dependency to your build.
2. Optionally configure application.properties.
3. Create REST controllers with mappings.
4. Run Spring Boot app.
5. Access /v3/api-docs for JSON spec.
6. Access /swagger-ui/index.html for interactive docs.

Full Transcript

To set up SpringDoc OpenAPI in a Spring Boot app, first add the SpringDoc dependency to your build file. This makes the OpenAPI tools available. Next, optionally configure application.properties to customize the docs. Then create REST controllers with @GetMapping or other mappings. When you run the app, SpringDoc scans these controllers and generates OpenAPI JSON at /v3/api-docs. You can also open /swagger-ui/index.html in your browser to see an interactive API documentation UI. This setup helps you document and test your API easily.