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Internet Engineering Task Force (IETF)                        P. HoffmanRequest for Comments: 7386                                VPN ConsortiumCategory: Standards Track                                       J. SnellISSN: 2070-1721                                             October 2014JSON Merge PatchAbstract   This specification defines the JSON merge patch format and processing   rules.  The merge patch format is primarily intended for use with the   HTTP PATCH method as a means of describing a set of modifications to   a target resource's content.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7386.Copyright Notice   Copyright (c) 2014 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Hoffman & Snell              Standards Track                    [Page 1]

RFC 7386                    JSON Merge Patch                October 2014Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Processing Merge Patch Documents  . . . . . . . . . . . . . .33.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .44.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .55.  Security Considerations . . . . . . . . . . . . . . . . . . .66.  References  . . . . . . . . . . . . . . . . . . . . . . . . .76.1.  Normative References  . . . . . . . . . . . . . . . . . .76.2.  Informative References  . . . . . . . . . . . . . . . . .7Appendix A.  Example Test Cases . . . . . . . . . . . . . . . . .8   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .9   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .91.  Introduction   This specification defines the JSON merge patch document format,   processing rules, and associated MIME media type identifier.  The   merge patch format is primarily intended for use with the HTTP PATCH   method [RFC5789] as a means of describing a set of modifications to a   target resource's content.   A JSON merge patch document describes changes to be made to a target   JSON document using a syntax that closely mimics the document being   modified.  Recipients of a merge patch document determine the exact   set of changes being requested by comparing the content of the   provided patch against the current content of the target document.   If the provided merge patch contains members that do not appear   within the target, those members are added.  If the target does   contain the member, the value is replaced.  Null values in the merge   patch are given special meaning to indicate the removal of existing   values in the target.   For example, given the following original JSON document:       {         "a": "b",         "c": {       "d": "e",       "f": "g"         }       }Hoffman & Snell              Standards Track                    [Page 2]

RFC 7386                    JSON Merge Patch                October 2014   Changing the value of "a" and removing "f" can be achieved by   sending:       PATCH /target HTTP/1.1       Host: example.org       Content-Type: application/merge-patch+json       {         "a":"z",         "c": {       "f": null         }       }   When applied to the target resource, the value of the "a" member is   replaced with "z" and "f" is removed, leaving the remaining content   untouched.   This design means that merge patch documents are suitable for   describing modifications to JSON documents that primarily use objects   for their structure and do not make use of explicit null values.  The   merge patch format is not appropriate for all JSON syntaxes.2.  Processing Merge Patch Documents   JSON merge patch documents describe, by example, a set of changes   that are to be made to a target resource.  Recipients of merge patch   documents are responsible for comparing the merge patch with the   current content of the target resource to determine the specific set   of change operations to be applied to the target.   To apply the merge patch document to a target resource, the system   realizes the effect of the following function, described in   pseudocode.  For this description, the function is called MergePatch,   and it takes two arguments: the target resource document and the   merge patch document.  The Target argument can be any JSON value or   undefined.  The Patch argument can be any JSON value.Hoffman & Snell              Standards Track                    [Page 3]

RFC 7386                    JSON Merge Patch                October 2014     define MergePatch(Target, Patch):       if Patch is an Object:         if Target is not an Object:       Target = {} # Ignore the contents and set it to an empty Object         for each Name/Value pair in Patch:       if Value is null:         if Name exists in Target:           remove the Name/Value pair from Target       else:         Target[Name] = MergePatch(Target[Name], Value)         return Target       else:         return Patch   There are a few things to note about the function.  If the patch is   anything other than an object, the result will always be to replace   the entire target with the entire patch.  Also, it is not possible to   patch part of a target that is not an object, such as to replace just   some of the values in an array.   The MergePatch operation is defined to operate at the level of data   items, not at the level of textual representation.  There is no   expectation that the MergePatch operation will preserve features at   the textual-representation level such as white space, member   ordering, number precision beyond what is available in the target's   implementation, and so forth.  In addition, even if the target   implementation allows multiple name/value pairs with the same name,   the result of the MergePatch operation on such objects is not   defined.3.  Example   Given the following example JSON document:       {         "title": "Goodbye!",         "author" : {       "givenName" : "John",       "familyName" : "Doe"         },         "tags":[ "example", "sample" ],         "content": "This will be unchanged"       }Hoffman & Snell              Standards Track                    [Page 4]

RFC 7386                    JSON Merge Patch                October 2014   A user agent wishing to change the value of the "title" member from   "Goodbye!" to the value "Hello!", add a new "phoneNumber" member,   remove the "familyName" member from the "author" object, and replace   the "tags" array so that it doesn't include the word "sample" would   send the following request:       PATCH /my/resource HTTP/1.1       Host: example.org       Content-Type: application/merge-patch+json       {         "title": "Hello!",         "phoneNumber": "+01-123-456-7890",         "author": {       "familyName": null         },         "tags": [ "example" ]       }   The resulting JSON document would be:       {         "title": "Hello!",         "author" : {       "givenName" : "John"         },         "tags": [ "example" ],         "content": "This will be unchanged",         "phoneNumber": "+01-123-456-7890"       }4.  IANA Considerations   This specification registers the following additional MIME media   types:      Type name: application      Subtype name: merge-patch+json      Required parameters: None      Optional parameters: None      Encoding considerations: Resources that use the "application/      merge-patch+json" media type are required to conform to the      "application/json" media type and are therefore subject to the      same encoding considerations specified inSection 8 of [RFC7159].Hoffman & Snell              Standards Track                    [Page 5]

RFC 7386                    JSON Merge Patch                October 2014      Security considerations: As defined in this specification      Published specification: This specification.      Applications that use this media type: None currently known.      Additional information:         Magic number(s): N/A         File extension(s): N/A         Macintosh file type code(s): TEXT      Person & email address to contact for further information: IESG      Intended usage: COMMON      Restrictions on usage: None      Author: James M. Snell <jasnell@gmail.com>      Change controller: IESG5.  Security Considerations   The "application/merge-patch+json" media type allows user agents to   indicate their intention for the server to determine the specific set   of change operations to be applied to a target resource.  As such, it   is the server's responsibility to determine the appropriateness of   any given change as well as the user agent's authorization to request   such changes.  How such determinations are made is considered out of   the scope of this specification.   All of the security considerations discussed inSection 5 of   [RFC5789] apply to all uses of the HTTP PATCH method with the   "application/merge-patch+json" media type.Hoffman & Snell              Standards Track                    [Page 6]

RFC 7386                    JSON Merge Patch                October 20146.  References6.1.  Normative References   [RFC7159]  Bray, T., "The JavaScript Object Notation (JSON) Data              Interchange Format",RFC 7159, March 2014,              <http://www.rfc-editor.org/info/rfc7159>.6.2.  Informative References   [RFC5789]  Dusseault, L. and J. Snell, "PATCH Method for HTTP",RFC5789, March 2010,              <http://www.rfc-editor.org/info/rfc5789>.Hoffman & Snell              Standards Track                    [Page 7]

RFC 7386                    JSON Merge Patch                October 2014Appendix A.  Example Test Cases   ORIGINAL        PATCH            RESULT   ------------------------------------------   {"a":"b"}       {"a":"c"}       {"a":"c"}   {"a":"b"}       {"b":"c"}       {"a":"b",                                    "b":"c"}   {"a":"b"}       {"a":null}      {}   {"a":"b",       {"a":null}      {"b":"c"}    "b":"c"}   {"a":["b"]}     {"a":"c"}       {"a":"c"}   {"a":"c"}       {"a":["b"]}     {"a":["b"]}   {"a": {         {"a": {         {"a": {     "b": "c"}       "b": "d",       "b": "d"   }                 "c": null}      }                   }               }   {"a": [         {"a": [1]}      {"a": [1]}     {"b":"c"}    ]   }   ["a","b"]       ["c","d"]       ["c","d"]   {"a":"b"}       ["c"]           ["c"]   {"a":"foo"}     null            null   {"a":"foo"}     "bar"           "bar"   {"e":null}      {"a":1}         {"e":null,                                    "a":1}   [1,2]           {"a":"b",       {"a":"b"}                    "c":null}   {}              {"a":            {"a":                    {"bb":           {"bb":                     {"ccc":          {}}}                      null}}}Hoffman & Snell              Standards Track                    [Page 8]

RFC 7386                    JSON Merge Patch                October 2014Acknowledgments   Many people contributed significant ideas to this document.  These   people include, but are not limited to, James Manger, Matt Miller,   Carsten Bormann, Bjoern Hoehrmann, Pete Resnick, and Richard Barnes.Authors' Addresses   Paul Hoffman   VPN Consortium   EMail: paul.hoffman@vpnc.org   James M. Snell   EMail: jasnell@gmail.comHoffman & Snell              Standards Track                    [Page 9]