2024-01-17 09:44:04 +01:00

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obj	website	rfc
concept	https://jsonpatch.com	https://datatracker.ietf.org/doc/html/rfc6902

JSONPatch

JSON Patch is a format for describing changes to a JSON document. It can be used to avoid sending a whole document when only a part has changed. When used in combination with the HTTP PATCH method, it allows partial updates for HTTP APIs in a standards compliant way.

The patch documents are themselves JSON documents.
A JSON Patch document is just a JSON file containing an array of patch operations. The patch operations supported by JSON Patch are “add”, “remove”, “replace”, “move”, “copy” and “test”. The operations are applied in order: if any of them fail then the whole patch operation should abort.

Simple example

The original document

{
  "baz": "qux",
  "foo": "bar"
}

The patch

[
  { "op": "replace", "path": "/baz", "value": "boo" },
  { "op": "add", "path": "/hello", "value": ["world"] },
  { "op": "remove", "path": "/foo" }
]

The result

{
  "baz": "boo",
  "hello": ["world"]
}

JSON Pointer

JSON Pointer (IETF RFC 6901) defines a string format for identifying a specific value within a JSON document. It is used by all operations in JSON Patch to specify the part of the document to operate on.

A JSON Pointer is a string of tokens separated by / characters, these tokens either specify keys in objects or indexes into arrays. For example, given the JSON

{
  "biscuits": [
    { "name": "Digestive" },
    { "name": "Choco Leibniz" }
  ]
}

/biscuits would point to the array of biscuits and /biscuits/1/name would point to "Choco Leibniz".

To point to the root of the document use an empty string for the pointer. The pointer / doesn’t point to the root, it points to a key of "" on the root (which is totally valid in JSON).

If you need to refer to a key with ~ or / in its name, you must escape the characters with ~0 and ~1 respectively. For example, to get "baz" from { "foo/bar~": "baz" } you’d use the pointer /foo~1bar~0.

Finally, if you need to refer to the end of an array you can use - instead of an index. For example, to refer to the end of the array of biscuits above you would use /biscuits/-. This is useful when you need to insert a value at the end of an array.

Operations

Add

{ "op": "add", "path": "/biscuits/1", "value": { "name": "Ginger Nut" } }

Adds a value to an object or inserts it into an array. In the case of an array, the value is inserted before the given index. The - character can be used instead of an index to insert at the end of an array.

Remove

{ "op": "remove", "path": "/biscuits" }

Removes a value from an object or array.

{ "op": "remove", "path": "/biscuits/0" }

Removes the first element of the array at biscuits (or just removes the “0” key if biscuits is an object)

Replace

{ "op": "replace", "path": "/biscuits/0/name", "value": "Chocolate Digestive" }

Replaces a value. Equivalent to a "remove" followed by an "add".

Copy

{ "op": "copy", "from": "/biscuits/0", "path": "/best_biscuit" }

Copies a value from one location to another within the JSON document. Both from and path are JSON Pointers.

Move

{ "op": "move", "from": "/biscuits", "path": "/cookies" }

Moves a value from one location to the other. Both from and path are JSON Pointers.

Test

{ "op": "test", "path": "/best_biscuit/name", "value": "Choco Leibniz" }

Tests that the specified value is set in the document. If the test fails, then the patch as a whole should not apply.

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