Java Tii: Spring Boot Interview QA Series Part 4

Introduction

• Continuation of the Spring Boot Interview QA series.
• Emphasis on practical implementations in RESTful web services.

RESTful Web Services & HTTP Methods

• HTTP Methods Used: Post, Put, Get, Patch, Delete.
  • Post: Create a resource.
  • Put: Update a resource.
  • Get: Retrieve a resource.
  • Patch: Partially update a resource.
  • Delete: Remove a resource.

Specifying HTTP Methods

• Annotations in Spring framework for HTTP methods:
  • Post Mapping: For inserting.
  • Put Mapping: For updating.
  • Get Mapping: For retrieving.
  • Patch Mapping: For partial updates.
  • Delete Mapping: For removing resources.
  • @RequestBody: Passing objects in Post and Put.
  • URL approach for Get and Delete.

RequestMapping & Specific Annotations

• @RequestMapping: Parent annotation that other HTTP methods extend from.
• Usage example for RequestMethod.

Designing REST Endpoints

Scenario 1:

• Design an endpoint to filter products by type using @GetMapping and @PathVariable.
• Example: /products/search/{productType}

Scenario 2:

• Design an endpoint with optional filtering using @GetMapping and @RequestParam. Returns all products if no filter is provided.
• Example: /filter?productType={type}

@PathVariable vs. @RequestParam

• @PathVariable: Mandatory input; part of URL.
• @RequestParam: Optional input; part of URL parameters.

RestController vs Controller

• @RestController: Simplified handling for returns (JSON/XML directly).
• @Controller: Requires @ResponseBody for non-view returns.

Deserializing JSON Request Payload

• Use @RequestBody to map JSON to a Java object.
• Example with Book and Author classes.

Updating with Post vs. Put

• Mix of update and insert should follow REST principles.
• Idempotency: Post (non-idempotent), Put (idempotent).

Request Body in Get Method

• Technically possible but not recommended.
• Get should use URL parameters.

Content Negotiation

• Enable to support multiple media types (JSON, XML) using @Produces and config properties.
• Example configuration entries in application.properties.

Common HTTP Status Codes

• 4xx: Client errors (400, 404, 401, 403, 405, 415).
• 5xx: Server errors (500, 502).
• 2xx: Success (200, 201).

Customizing Status Codes

• Use @ResponseStatus for custom HTTP responses.

Enabling Cross-Origin (CORS)

• @CrossOrigin: Annotation or using Java-based config for allowed origins/hosts/ports.

File Upload in Spring Boot

• Use MultipartFile data type.
• Example: File upload handler in a controller.

API Versioning

• Strategies: URI path, request parameters, headers.
• Example implementations for FlightBookingController.

API Documentation

• Use Swagger (Open API 3) for auto-documentation.
• Example dependencies and config entries.

Hiding Endpoints in Documentation

• @Hidden: Annotation to hide specific endpoints in Swagger.

Consuming REST APIs

• Approaches: RestTemplate, FeignClient, WebClient, Advanced Rest Client.
• Examples for each with dependencies and usage instructions.

Conclusion

• Inviting audience to engage and ask questions.