Applications Area Working Group P. Bryan, Ed.
Internet-Draft Salesforce.com
Intended status: Informational M. Nottingham, Ed.
Expires: April 25, 2013 October 22, 2012
JSON Patch
draft-ietf-appsawg-json-patch-06
Abstract
JSON Patch defines the media type "application/json-patch", a JSON
document structure for expressing a sequence of operations to apply
to a JSON document.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 25, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Document Structure . . . . . . . . . . . . . . . . . . . . . . 3
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. add . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. remove . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.3. replace . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.4. move . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.5. copy . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.6. test . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . . 10
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 10
A.1. Adding an Object Member . . . . . . . . . . . . . . . . . 10
A.2. Adding an Array Element . . . . . . . . . . . . . . . . . 11
A.3. Removing an Object Member . . . . . . . . . . . . . . . . 11
A.4. Removing an Array Element . . . . . . . . . . . . . . . . 11
A.5. Replacing a Value . . . . . . . . . . . . . . . . . . . . 12
A.6. Moving a Value . . . . . . . . . . . . . . . . . . . . . . 12
A.7. Moving an Array Element . . . . . . . . . . . . . . . . . 13
A.8. Testing a Value: Success . . . . . . . . . . . . . . . . . 14
A.9. Testing a Value: Error . . . . . . . . . . . . . . . . . . 14
A.10. Adding a nested Member Object . . . . . . . . . . . . . . 14
A.11. Ignoring Unrecognized Elements . . . . . . . . . . . . . . 15
A.12. Adding to a Non-existant Target . . . . . . . . . . . . . 15
A.13. Invalid JSON Patch Document . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
JavaScript Object Notation (JSON) [RFC4627] is a common format for
the exchange and storage of structured data. HTTP PATCH [RFC5789]
extends the Hypertext Transfer Protocol (HTTP) [RFC2616] with a
method to perform partial modifications to resources.
JSON Patch is a format (identified by the media type "application/
json-patch") for expressing a sequence of operations to apply to a
target JSON document, suitable for use with the HTTP PATCH method.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
See Section 5 for information about handling errors.
3. Document Structure
A JSON Patch document is a JSON [RFC4627] document whose root is an
array of objects. Each object represents a single operation to be
applied to the target JSON document.
An example JSON Patch document:
[
{ "op": "test", "path": "/a/b/c", "value": "foo" },
{ "op": "remove", "path": "/a/b/c" },
{ "op": "add", "path": "/a/b/c", "value": [ "foo", "bar" ] },
{ "op": "replace", "path": "/a/b/c", "value": 42 },
{ "op": "move", "path": "/a/b/c", "to": "/a/b/d" },
{ "op": "copy", "path": "/a/b/d", "to": "/a/b/e" }
]
Evaluation of a JSON Patch document begins with a target JSON
document. Operations are applied sequentially in the order they
appear in the array. Each operation in the sequence is applied to
the target document; the resulting document becomes the target of the
next operation. Evaluation continues until all operations are
successfully applied, or an error condition is encountered.
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4. Operations
Operation objects MUST have exactly one "op" member, whose value
indicates the operation to perform. Its value MUST be one of "add",
"remove", "replace", "move", "copy" or "test". The semantics of each
is defined below.
Additionally, operation objects MUST have exactly one "path" member,
whose value MUST be a string containing a [JSON-Pointer] value that
references the location within the target document to perform the
operation (the "target location").
Other members of operation objects MUST be ignored, unless they are
explicitly allowed by the definition of the operation.
Note that the ordering of members in JSON objects is not significant;
therefore, the following operations are equivalent:
{ "op": "add", "path": "/a/b/c", "value": "foo" }
{ "path": "/a/b/c", "op": "add", "value": "foo" }
{ "value": "foo", "path": "/a/b/c", "op": "add" }
4.1. add
The "add" operation adds a new value at the target location. The
operation object MUST contain a "value" member that specifies the
value to be added.
When the operation is applied, the target location MUST reference one
of:
o the root of the target document,
o a member to add to an existing object, or
o an element to add to an existing array.
For example:
{ "op": "add", "path": "/a/b/c", "value": [ "foo", "bar" ] }
If the target location references an element of an existing array,
any elements at or above the specified index are shifted one position
to the right. The specified index MUST NOT be greater than the
number of elements in the array.
When the "-" character is used to index the end of the array, this
has the effect of appending the value to the array.
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Note that this operation will, in common use, have a target location
that does not resolve to an existing value, resulting in the
pointer's error handling algorithm being invoked. This specification
defines the error handling algorithm for "add" pointers to explicitly
ignore the error and perform the operation as specified.
4.2. remove
The "remove" operation removes the value at the target location.
The target location MUST exist for the operation to be successful.
For example:
{ "op": "remove", "path": "/a/b/c" }
If removing an element from an array, any elements above the
specified index are shifted one position to the left.
4.3. replace
The "replace" operation replaces the value at the target location
with a new value. The operation object MUST contain a "value" member
that specifies the replacement value.
The target location MUST exist for the operation to be successful.
For example:
{ "op": "replace", "path": "/a/b/c", "value": 42 }
This operation is functionally identical to expressing a "remove"
operation for a value, followed immediately by an "add" operation at
the same location with the replacement value.
4.4. move
The "move" operation removes the value at the target location and
adds it to another location.
The operation object MUST contain a "to" member, a string containing
a JSON Pointer value that references the location in the target
document to add the value to.
The "to" location MUST reference one of:
o the member to add to an existing object, or
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o an element to add to an existing array.
For example:
{ "op": "move", "path": "/a/b/c", "to": "/a/b/d" }
This operation is functionally identical to expressing a "remove"
operation on the target location, followed immediately by an "add"
operation at the "to" location with the value that was just removed.
The location in the "to" member MUST NOT be part of the location
defined by "path"; i.e., a location cannot be moved into one of its
children.
The location in the "to" member MUST NOT reference a member of an
existing object in the target document, unless "path" and "to"
specify the same object, which has no effect.
If the location in the "to" member references an element of an
existing array, any elements at or above the specified index are
shifted one position to the right. The specified index MUST NOT be
greater than the number of elements in the array.
4.5. copy
The "copy" operation copies the value at the target location to
another location.
The operation object MUST contain a "to" member, a string containing
a JSON Pointer value that references the location in the target
document to add the value to.
This location MUST reference one of:
o the member to add to an existing object, or
o an element to add to an existing array.
For example:
{ "op": "copy", "path": "/a/b/c", "to": "/a/b/e" }
The location in the "to" member MUST NOT be part of the location
defined by "path"; i.e., a location cannot be copied into one of its
children.
The location in the "to" member MUST NOT reference a member of an
existing object in the target document, unless "path" and "to"
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specify the same object, which has no effect.
If the location in the "to" member references an element of an
existing array, any elements at or above the specified index are
shifted one position to the right. The specified index MUST NOT be
greater than the number of elements in the array.
4.6. test
The "test" operation tests that a value at the target location is
equal to a specified value.
The operation object MUST contain a "value" member that conveys the
value to be compared to that at the target location.
The target location MUST be equal to the "value" value for the
operation to be considered successful.
Here, "equal" means that the value at the target location and the
value conveyed by "value" are of the same JSON type, and considered
equal by the following rules for that type:
o strings: are considered equal if, after unescaping any sequence(s)
in both strings starting with a reverse solidus, they contain the
same number of Unicode characters and their code points are
position-wise equal.
o numbers: are considered equal if subtracting one from the other
results in 0.
o arrays: are considered equal if they contain the same number of
values, and each value can be considered equal to the value at the
corresponding position in the other array.
o objects: are considered equal if they contain the same number of
members, and each member can be considered equal to a member in
the other object, by comparing their keys as strings, and values
using this list of type-specific rules.
o literals (false, true and null): are considered equal if they are
the same.
Note that this is a logical comparison; e.g., whitespace between the
member values of an array is not significant.
Also, note that ordering of the serialisation of object members is
not significant.
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For example:
{ "op": "test", "path": "/a/b/c", "value": "foo" }
5. Error Handling
If a RFC2119 [RFC2119] requirement is violated by a JSON Patch
document, or if an operation is not successful, evaluation of the
JSON Patch document SHOULD terminate and application of the entire
patch document SHALL NOT be deemed successful.
See [RFC5789], Section 2.2 for considerations regarding handling
errors when JSON Patch is used with the HTTP PATCH method, including
suggested status codes to use to indicate various conditions.
Note that as per [RFC5789], when used with the PATCH HTTP method, it
is atomic. Therefore, the following patch would result in no changes
being made to the document at all (because the "test" operation
results in an error).
[
{ "op": "replace", "path": "/a/b/c", "value": 42 },
{ "op": "test", "path": "/a/b/c", "value": "C" }
]
6. IANA Considerations
The Internet media type for a JSON Patch document is application/
json-patch.
Type name: application
Subtype name: json-patch
Required parameters: none
Optional parameters: none
Encoding considerations: binary
Security considerations:
See Security Considerations in section 7.
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Interoperability considerations: N/A
Published specification:
[this memo]
Applications that use this media type:
Applications that manipulate JSON documents.
Additional information:
Magic number(s): N/A
File extension(s): .json-patch
Macintosh file type code(s): TEXT
Person & email address to contact for further information:
Paul C. Bryan <pbryan@anode.ca>
Intended usage: COMMON
Restrictions on usage: none
Author: Paul C. Bryan <pbryan@anode.ca>
Change controller: IETF
7. Security Considerations
This specification has the same security considerations as JSON
[RFC4627] and [JSON-Pointer].
8. Acknowledgements
The following individuals contributed ideas, feedback and wording to
this specification:
Mike Acar, Mike Amundsen, Paul Davis, Murray S. Kucherawy, Dean
Landolt, Randall Leeds, James Manger, Julian Reschke, James Snell,
Eli Stevens.
The structure of a JSON Patch document was influenced by the XML
Patch document [RFC5261] specification.
9. References
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9.1. Normative References
[JSON-Pointer]
Bryan, P. and K. Zyp, "JSON Pointer",
draft-ietf-appsawg-json-pointer-04 (work in progress),
March 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
9.2. Informative References
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC5261] Urpalainen, J., "An Extensible Markup Language (XML) Patch
Operations Framework Utilizing XML Path Language (XPath)
Selectors", RFC 5261, September 2008.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, March 2010.
Appendix A. Examples
A.1. Adding an Object Member
An example target JSON document:
{
"foo": "bar"
}
A JSON Patch document:
[
{ "op": "add", "path": "/baz", "value": "qux" }
]
The resulting JSON document:
{
"baz": "qux",
"foo": "bar"
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}
A.2. Adding an Array Element
An example target JSON document:
{
"foo": [ "bar", "baz" ]
}
A JSON Patch document:
[
{ "op": "add", "path": "/foo/1", "value": "qux" }
]
The resulting JSON document:
{
"foo": [ "bar", "qux", "baz" ]
}
A.3. Removing an Object Member
An example target JSON document:
{
"baz": "qux",
"foo": "bar"
}
A JSON Patch document:
[
{ "op": "remove", "path": "/baz" }
]
The resulting JSON document:
{
"foo": "bar"
}
A.4. Removing an Array Element
An example target JSON document:
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{
"foo": [ "bar", "qux", "baz" ]
}
A JSON Patch document:
[
{ "op": "remove", "path": "/foo/1" }
]
The resulting JSON document:
{
"foo": [ "bar", "baz" ]
}
A.5. Replacing a Value
An example target JSON document:
{
"baz": "qux",
"foo": "bar"
}
A JSON Patch document:
[
{ "op": "replace", "path": "/baz", "value": "boo" }
]
The resulting JSON document:
{
"baz": "boo",
"foo": "bar"
}
A.6. Moving a Value
An example target JSON document:
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{
"foo": {
"bar": "baz",
"waldo": "fred"
}
"qux": {
"corge": "grault"
}
}
A JSON Patch document:
[
{ "op": "move", "path": "/foo/waldo", to: "/qux/thud" }
]
The resulting JSON document:
{
"foo": {
"bar": "baz"
}
"qux": {
"corge": "grault",
"thud": "fred"
}
}
A.7. Moving an Array Element
An example target JSON document:
{
"foo": [ "all", "grass", "cows", "eat" ]
}
A JSON Patch document:
[
{ "op": "move", "path": "/foo/1", "to": "/foo/3" }
]
The resulting JSON document:
{
"foo": [ "all", "cows", "eat", "grass" ]
}
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A.8. Testing a Value: Success
An example target JSON document:
{
"baz": "qux",
"foo": [ "a", 2, "c" ]
}
A JSON Patch document that will result in successful evaluation:
[
{ "op": "test", "path": "/baz", "value": "qux" },
{ "op": "test", "path": "/foo/1", "value": 2 }
]
A.9. Testing a Value: Error
An example target JSON document:
{
"baz": "qux"
}
A JSON Patch document that will result in an error condition:
[
{ "op": "test", "path": "/baz", "value": "bar" }
]
A.10. Adding a nested Member Object
An example target JSON document:
{
"foo": "bar"
}
A JSON Patch document:
[
{ "op": "add", "path": "/child", "value": { "grandchild": { } } }
]
The resulting JSON document:
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{
"foo": "bar",
"child": {
"grandchild": {
}
}
}
A.11. Ignoring Unrecognized Elements
An example target JSON document:
{
"foo":"bar"
}
A JSON Patch document:
[
{ "op":"add", "path":"/baz", "value":"qux", "xyz":123 }
]
The resulting JSON document:
{
"foo":"bar",
"baz":"qux"
}
A.12. Adding to a Non-existant Target
An example target JSON document:
{
"foo": "bar"
}
A JSON Patch document:
[
{ "op": "add", "path": "/baz/bat", "value": "qux" }
]
This JSON Patch document, applied to the target JSON document above,
would result in an error (therefore not being applied) because the
"add" operation's target location that references neither the root of
the document, nor a member of an existing object, nor a member of an
existing array.
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A.13. Invalid JSON Patch Document
A JSON Patch document:
[
{ "op":"add", "path":"/baz", "value":"qux", "op":"remove" }
]
This JSON Patch document cannot be treated as an "add" operation
since there is a later "op":"remove" element. A JSON parser that
hides such duplicate element names therefore cannot be used unless it
always exposes only the last element with a given name (eg
"op":"remove" in this example).
Authors' Addresses
Paul C. Bryan (editor)
Salesforce.com
Phone: +1 604 783 1481
Email: pbryan@anode.ca
Mark Nottingham (editor)
Email: mnot@mnot.net
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