spring-boot-rest-api

Modern applications expose APIs for frontend clients, mobile apps, and third-party integrations. Building RESTful APIs requires mapping HTTP methods to operations, serializing/deserializing JSON, handling status codes, and managing request/response formats. Without good tooling, this involves significant boilerplate.

Spring Boot makes REST API development effortless by combining @RestController for request handling, auto-configured Jackson for JSON serialization, embedded Tomcat for serving, and Actuator for monitoring. A single @SpringBootApplication class and a few controller methods produce a production-ready REST API.

1. @RestController: @Controller + @ResponseBody — every method returns data (JSON/XML), not view names
2. Request mapping: @GetMapping, @PostMapping, @PutMapping, @DeleteMapping map HTTP verbs and URLs
3. Request binding: @PathVariable, @RequestParam, @RequestBody bind request data to method parameters
4. Response serialization: Jackson (auto-configured) serializes Java objects to JSON; @JsonIgnore, @JsonProperty control output
5. Status codes: @ResponseStatus(HttpStatus.CREATED) or ResponseEntity for full control
6. Exception handling: @RestControllerAdvice provides consistent JSON error responses across all endpoints
7. Documentation: Spring Boot integrates with Swagger/OpenAPI for auto-generated API docs

• RESTful mapping: One annotation per HTTP verb — @GetMapping, @PostMapping, @PutMapping, @DeleteMapping, @PatchMapping
• Content negotiation: Jackson serializes to JSON by default; XML if Jackson XML extension is on classpath
• ResponseEntity: Full control over status, headers, and body — ResponseEntity.created(location).body(savedUser)
• Request validation: @Valid + BindingResult for request body validation
• HATEOAS: Spring HATEOAS adds link support for hypermedia-driven APIs
• Testing: MockMvc and WebTestClient for comprehensive REST API testing

• Built from: Spring Boot — Boot auto-configures the web stack for REST APIs
• Built from: Spring Controller — @RestController is a specialized @Controller
• Related: JAX-RPC — JAX-RPC is XML-based SOAP; Spring Boot REST is JSON-based, lighter
• Builds into: Java Microservices — REST APIs are the communication backbone of microservices
• Related: HTTP Protocol — REST APIs use HTTP semantics (methods, status codes, headers)

• Circular references: Bidirectional JPA relationships cause infinite JSON serialization — use @JsonIgnore or @JsonManagedReference/@JsonBackReference
• Global prefix: All APIs under /api/v1/ — set server.servlet.context-path or use RequestMapping at class level
• Content-type mismatch: Client sends wrong Content-Type → 415 Unsupported Media Type
• Versioning: URL path versioning (/v1/users) vs header versioning (Accept: application/vnd.company.v1+json)
• CORS: Browsers block cross-origin requests; @CrossOrigin or WebMvcConfigurer.addCorsMappings() to allow