Internet Engineering Task Force P. Bryan, Ed.
Internet-Draft ForgeRock US, Inc.
Intended status: Informational April 20, 2011
Expires: October 22, 2011
A JSON Media Type for Describing Partial Modifications to JSON Documents
draft-pbryan-json-patch-00
Abstract
JSON (JavaScript Object Notation) Patch defines the media type
"application/patch+json", a JSON-based document structure for
specifying partial modifications 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.
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This Internet-Draft will expire on October 22, 2011.
Copyright Notice
Copyright (c) 2011 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Patch Object Structure . . . . . . . . . . . . . . . . . . . . 3
3.1. patches . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. op . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.3. path . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.4. element . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.5. value . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Patch Operations . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. add . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. remove . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . . 6
A.1. Adding an Object Property . . . . . . . . . . . . . . . . . 6
A.2. Adding an Array Element . . . . . . . . . . . . . . . . . . 7
A.3. Removing an Object Property . . . . . . . . . . . . . . . . 7
A.4. Removing an Array Element . . . . . . . . . . . . . . . . . 8
A.5. Replacing a Value . . . . . . . . . . . . . . . . . . . . . 8
Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . . 9
Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
JavaScript Object Notation (JSON) [RFC4627] has become a popular
format for the storage and transmission of structured data between
systems. As a result, numerous web service APIs support the JSON
media type. The HTTP PATCH [RFC5789] specification extends HTTP with
a new method to perform partial modifications to resources.
This Internet-Draft proposes the JSON-Patch media type "application/
patch+json", a JSON-based document structure for specifying partial
modifications to apply to a JSON document.
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].
3. Patch Object Structure
A JSON-Patch document is a JSON document that contains an object
which specifies the set of operations to apply to a target JSON
document.
An example JSON-Patch document:
{
"patches": [
{ "op": "remove", "path": "$.a.b.c" },
{ "op": "add", "path": "$.a.b", "element": "c", "value": "foo" }
]
}
3.1. patches
An array of objects; each object specifies a single patch operation
to be applied to the target JSON document. Patch operations MUST be
applied sequentially in the order they appear in the array. After
the first patch has been applied, the resulting JSON document becomes
the target for the next patch operation. This process repeats until
all patches have been applied.
3.2. op
MUST be a string value. Specifies the patch operation to be applied.
Defined patch operations are "add" and "remove".
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3.3. path
MUST be a string value. Contains a concrete [JSONPath] expression
(i.e. MUST contain only the root $, object property . [] and array
subscript [] operators). It is an error condition if a path resolves
to anything but a single node within the target JSON document.
3.4. element
MUST be a string or integer value. Specifies the child node to add
into the node specified by the path. If string, specifies an object
property to insert; if integer, specifies an array index to insert
at. It is an error condition if the specified node type is
incompatible with the "element" value (i.e. object with integer
element, array with string element).
3.5. value
The value to insert into the specified node.
4. Patch Operations
The patch operations are "add" and "remove".
4.1. add
Adds a new property into an object or element into an array.
If adding a property into an object, the "element" specifies the
property to be added. It is an error condition if the property
already exists in the object.
If adding into an array, the "element" specifies the index where the
value should be inserted. Any elements at or above the specified
index are shifted one position to the right (i.e. indexes are
incremented). It is an error condition if an addition would result
in sparse allocation of array element(s).
4.2. remove
Removes the node specified by the path. It is an error condition if
the node to be removed does not exist.
If removing an element from an array, any elements above the
specified index are shifted one position to the left (i.e. indexes
are decremented).
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5. Error Handling
In the event of an error condition, whether patch processing ceases,
and/or how error conditions are communicated and handled are left to
the implementation to specify.
Enforcing safety and/or idempotency of a JSON patch document is
specified and handled by the implementation, based-on any mechanisms
in other related specifications, such as HTTP [RFC2616] and HTTP
PATCH [RFC5789].
6. Acknowledgements
The structure of a JSON patch document was informed by the XML Patch
document [RFC5261] specification.
7. IANA Considerations
The proposed MIME media type for the JSON patch document is
"application/patch+json".
Type name: application
Subtype name: patch+json
Required parameters: none
Optional parameters: none
8. Security Considerations
This specification is based-on the JSON format, therefore has the
same security considerations as [RFC4627].
This specification uses [JSONPath] expressions to resolve the nodes
to be modified. Such expressions should not be evaluated directly by
the implementation language interpreter due to the potential for
injection of malicious code.
9. References
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9.1. Normative References
[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
[JSONPath]
Goessner, S., "JSONPath: XPath for JSON", April 2007,
<http://goessner.net/articles/JsonPath/>.
[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 Property
An example target JSON document:
{
"foo": "bar"
}
A JSON patch document:
{
"patches": [
{ "op": "add", "path": "$", "element": "baz", "value": "qux" }
]
}
The resulting JSON document:
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{
"baz": "qux",
"foo": "bar"
}
A.2. Adding an Array Element
An example target JSON document:
{
"foo": ["bar", "baz"]
}
A JSON patch document:
{
"patches": [
{ "op": "add", "path": "$.foo", "element": 1, "value": "qux" }
]
}
The resulting JSON document:
{
"foo": [ "bar", "qux", "baz" ]
}
A.3. Removing an Object Property
An example target JSON document:
{
"baz": "qux",
"foo": "bar"
}
A JSON patch document:
{
"patches": [
{ "op": "remove", "path": "$.baz" }
]
}
The resulting JSON document:
{
"foo": "bar"
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}
A.4. Removing an Array Element
An example target JSON document:
{
"foo": [ "bar", "qux", "baz" ]
}
A JSON patch document:
{
"patches": [
{ "op": "remove", "path": "$.foo[1]" }
]
}
The resulting JSON document:
{
"foo": ["bar", "baz"]
}
A.5. Replacing a Value
Replacing a value is performed by removing a value and inserting it.
An example target JSON document:
{
"baz": "qux",
"foo": "bar"
}
A JSON patch document:
{
"patches": [
{ "op": "remove", "path": "$.baz" },
{ "op": "add", "path": "$", "element": "baz": "value": "boo" }
]
}
The resulting JSON document:
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{
"baz": "boo",
"foo": "bar"
}
Appendix B. Changelog
Draft 00
o Initial draft.
Appendix C. Open Issues
1. [JSONPath] is an informal, de facto standard. Work is now in
progress to get it published an Internet-Draft (with some likely
changes).
2. Should define an accompanying JSON-Schema specification for the
JSON-Patch document structure.
Author's Address
Paul C. Bryan (editor)
ForgeRock US, Inc.
201 NE Park Plaza Drive Suite 196
Vancouver, WA 98684
USA
Phone: +1 604 783 1481
Email: paul.bryan@forgerock.com
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