spring-boot-tutorial-3f.java

@PostMapping("/products")
public ResponseEntity<Product> createProduct(@RequestBody Product request) {
    boolean isIdDuplicated = productDB.stream()
            .anyMatch(p -> p.getId().equals(request.getId()));
    if (isIdDuplicated) {
        return ResponseEntity.status(HttpStatus.CONFLICT).build();
    }

    Product product = new Product();
    product.setId(request.getId());
    product.setName(request.getName());
    product.setPrice(request.getPrice());
    productDB.add(product);

    URI location = ServletUriComponentsBuilder
            .fromCurrentRequest()
            .path("/{id}")
            .buildAndExpand(product.getId())
            .toUri();

    return ResponseEntity.created(location).body(product);
}