PATCH in REST and null - rest

Question

We have an article resource with properties:
title
image
description
status: published | draft
if we want only to remove image we make request
{title: null, image: null, description: null, status: null}
if we want only to update status we make request
{title: null, image: null, description: null, status: draft}
but in this case image also will be removed
How in REST to update only one property?

Answer 1

Performing partial modifications to a resource
The PATCH method can be used to perform partial modifications to a resource. The request payload should contain a set of instructions describing how the resource will be modified. See the following quote from the RFC 5789:
2. The PATCH Method
The PATCH method requests that a set of changes described in the request entity be applied to the resource identified by the Request-URI. [...]
The difference between the PUT and PATCH requests is reflected in the way the server processes the enclosed entity to modify the resource identified by the Request-URI. In a PUT request, the enclosed entity is considered to be a modified version of the resource stored on the origin server, and the client is requesting that the stored version be replaced. With PATCH, however, the enclosed entity contains a set of instructions describing how a resource currently residing on the origin server should be modified to produce a new version. [...]
To describe such set of instructions, you can use JSON Patch defined in the RFC 6902:
1. Introduction
JSON Patch is a format (identified by the media type application/json-patch+json) for expressing a sequence of operations to apply to a target JSON document; it is suitable for use with the HTTP PATCH method.
This format is also potentially useful in other cases in which it is necessary to make partial updates to a JSON document or to a data structure that has similar constraints [...]
Examples with JSON Patch
To update the status, you can do the following:
PATCH /articles/1 HTTP/1.1
Host: example.com
Content-Type: application/json-patch+json
[
{ "op": "replace", "path": "/status", "value": "draft" }
]
Use the following to remove the image:
PATCH /articles/1 HTTP/1.1
Host: example.com
Content-Type: application/json-patch+json
[
{ "op": "remove", "path": "/image" }
]
And use the following to update the status and remove the image:
PATCH /articles/1 HTTP/1.1
Host: example.com
Content-Type: application/json-patch+json
[
{ "op": "replace", "path": "/status", "value": "draft" },
{ "op": "remove", "path": "/image" }
]
Alternatively to JSON Patch, you may want to consider JSON Merge Patch defined in the RFC 7396: it's also a means of describing a set of modifications to a target resource's content.

Answer 2

Let me give an example which troubles me when using JSON-Patch message in PATCH message in a RESTFul API.
If we have a structure like:
{"books": [
{"title": "HTTP-Protocol", "image": "http.jpg", "description": "A standard book on HTTP", "status": "Available"},
{"title": "JSON-Patch", "image": "patching.jpg", "description": "Explanation on how to use json-patch in RESTFul", "status": "Planned"},
{"title": "RESTFul", "image": "fielding.jpg", "description": "Representational state transfer", "status": "Available"}
]}
Now the client who requested this information wants to change the status of the third book (RESTFul) from "Available" to "Borrowed".
Using JSON-Patch he would send the following message:
[
{
"op": "replace",
"path": "/books/2/status",
"value": "Borrowed"
}
]
Meaning that from the list, as he saw it, he wants to change the status of the third item. But since a RESTFul API call is stateless the server does not know anymore what list it gave to the client. Maybe in the mean time a new book was added and the list on the server change to:
{"books": [
{"title": "HTTP-Protocol", "image": "http.jpg", "description": "A standard book on HTTP", "status": "Available"},
{"title": "In between", "image": "destroy.jpg", "description": "Not RESTFul?", "status": "Available"},
{"title": "JSON-Patch", "image": "patching.jpg", "description": "Explanation on how to use json-patch in RESTFul", "status": "Planned"},
{"title": "RESTFul", "image": "fielding.jpg", "description": "Representational state transfer", "status": "Available"}
]}
Then this json-patch message received from the client will change the book with the title "JSON-Patch" and not the book with title "RESTFul" as intended by the client.
What is in your opinion the solution for this problem?