java 36 lines · 8 steps

Batch JSON Merge Patch in Spring

A Spring REST endpoint applies RFC 7396 JSON merge patches to many products in one request.

Explained by highlit

Spring Intermediate json-merge-patch rest-api partial-update batch-processing exception-handling

1@RestController
2@RequestMapping("/api/products")
3@RequiredArgsConstructor
4public class ProductBatchController {
5 
6    private final ProductRepository productRepository;
7    private final ObjectMapper objectMapper;
8 
9    @PatchMapping(path = "/batch", consumes = "application/merge-patch+json")
10    public ResponseEntity<List<ProductDto>> patchBatch(@RequestBody List<BatchPatch> patches) {
11        List<ProductDto> updated = new ArrayList<>(patches.size());
12 
13        for (BatchPatch patch : patches) {
14            Product product = productRepository.findById(patch.id())
15                    .orElseThrow(() -> new ProductNotFoundException(patch.id()));
16 
17            Product merged = applyMergePatch(patch.patch(), product);
18            updated.add(ProductDto.from(productRepository.save(merged)));
19        }
20 
21        return ResponseEntity.ok(updated);
22    }
23 
24    private Product applyMergePatch(JsonNode patch, Product target) {
25        try {
26            ObjectNode current = objectMapper.valueToTree(target);
27            JsonNode result = JsonMergePatch.fromJson(patch).apply(current);
28            return objectMapper.treeToValue(result, Product.class);
29        } catch (JsonPatchException | JsonProcessingException e) {
30            throw new InvalidPatchException("Unable to apply merge patch for product " + target.getId(), e);
31        }
32    }
33 
34    public record BatchPatch(@NotNull Long id, @NotNull JsonNode patch) {
35    }
36}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1JSON Merge Patch lets clients send only the fields they want changed, and the server merges them onto the existing entity.
2Serializing an entity to a JsonNode, applying the patch, then deserializing back gives a clean way to do partial updates without manual field mapping.
3Wrapping library-specific exceptions in a domain exception keeps patch failures meaningful to API callers.

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