Perform FHIR JSON Patch to update specific fields of a resource without replacing the entire resource
domain: hl7.org · 6 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Confirm the server supports PATCH by checking the CapabilityStatement for patch in the interaction list for the target resource type
Read the current resource with GET [base]/[ResourceType]/[id] and note the current versionId from meta.versionId for optimistic concurrency
Construct a JSON Patch document (RFC 6902) as a JSON array of patch operations: op (add, remove, replace, move, copy, test), path (JSON Pointer to the target field), and value
Send PATCH [base]/[ResourceType]/[id] with Content-Type: application/json-patch+json and the If-Match: W/"[versionId]" header to enforce optimistic locking
On 200 OK or 204, parse the updated resource from the response body (if returned) or re-read the resource to confirm the patch was applied correctly
Handle 412 Precondition Failed (version conflict) by re-reading the resource, rebasing the patch if still applicable, and retrying
Known gotchas
JSON Patch paths use JSON Pointer syntax (RFC 6901) where array elements are addressed by zero-based index (e.g., /name/0/family); incorrect paths cause 400 errors
Omitting the If-Match header may be accepted by some servers but leaves the operation non-idempotent and subject to lost-update races; always include it in production
Some FHIR servers require the test operation at the start of the patch array to validate preconditions before applying mutations; verify server behavior and add test ops for critical fields
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