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 working documents as Internet-Drafts. The list of current Internet- Drafts is at http:/⁠/⁠datatracker.ietf.org/⁠drafts/⁠current/⁠.

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This Internet-Draft will expire on April 23, 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 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.

Table of Contents

• 1. Introduction
• 2. Conventions
• 3. Document Structure
• 4. Operations
• 4.1. add
• 4.2. remove
• 4.3. replace
• 4.4. move
• 4.5. copy
• 4.6. test
• 5. Error Handling
• 6. IANA Considerations
• 7. Security Considerations
• 8. Acknowledgements
• 9. References
• 9.1. Normative References
• 9.2. Informative References
• Appendix A. Examples
• Appendix A.1. Adding an Object Member
• Appendix A.2. Adding an Array Element
• Appendix A.3. Removing an Object Member
• Appendix A.4. Removing an Array Element
• Appendix A.5. Replacing a Value
• Appendix A.6. Moving a Value
• Appendix A.7. Moving an Array Element
• Appendix A.8. Testing a Value: Success
• Appendix A.9. Testing a Value: Error
• Appendix A.10. Adding a nested Member Object
• Appendix A.11. Ignoring Unrecognized Elements
• Appendix A.12. Adding to a Non-existant Target
• Appendix A.13. Invalid JSON Patch Document
• Authors' Addresses

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.

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:

• the root of the target document,
• a member to add to an existing object, or
• 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.

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:

• the member to add to an existing object, or
• 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:

• the member to add to an existing object, or
• 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" 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:

• 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.
• numbers: are considered equal if subtracting one from the other results in 0.
• 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.
• 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.
• 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.

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.

Interoperability considerations:

N/A

Published specification:

[this memo]

Applications that use this media type:

Applications that manipulate JSON documents.

Additional information:

• N/A
• .json-patch
• 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

9.1. Normative References

9.2. Informative References

Appendix A. Examples

Appendix 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"
}
                 

Appendix 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" ]
}
                 

Appendix 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"
}
                 

Appendix A.4. Removing an Array Element

An example target JSON document:

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

A JSON Patch document:

[
  { "op": "remove", "path": "/foo/1" }
]
                 

The resulting JSON document:

{
  "foo": [ "bar", "baz" ]
}
                 

Appendix 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"
}
                 

Appendix A.6. Moving a Value

An example target JSON document:

{
  "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"
  }
}
                 

Appendix 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" ]
}
                 

Appendix 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 }
]
                 

Appendix 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" }
]
                 

Appendix 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:

{
  "foo": "bar",
  "child": {
    "grandchild": {
    }
  }
}
                 

Appendix 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"
}
                 

Appendix 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.

Appendix 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