JSON Patch
draft-ietf-appsawg-json-patch-02

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/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on January 02, 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
• 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.

The JSON Patch media type "application/json-patch" is a JSON document structure 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].

3. Document Structure

A JSON Patch document contains a JSON array of objects. Each object contains a single operation to apply to the target JSON document.

An example JSON Patch document:

[
    { "test": "/a/b/c", "value": "foo" },
    { "remove": "/a/b/c" },
    { "add": "/a/b/c", "value": [ "foo", "bar" ] },
    { "replace": "/a/b/c", "value": 42 },
    { "move": "/a/b/c", "to": "/a/b/d" },
    { "copy": "/a/b/c", "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

The operation to perform is expressed in a member of the operation object. The name of the operation member is one of: "add", "remove", "replace", "move", "copy" or "test".

The member value is a string containing a [JSON-Pointer] value that references the location within the target document to perform the operation. It is an error condition if an operation object contains no recognized operation member or more than one operation member.

4.1. add

The "add" operation adds a new value at the specified location in the target document. The 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. The operation object contains a "value" member that specifies the value to be added.

Example:

{ "add": "/a/b/c", "value": [ "foo", "bar" ] }
             

If the location references the root of the target document or a member of an existing object, it is an error condition if a value at the specified location already exists.

If the location references an element of an existing array, any elements at or above the specified index are shifted one position to the right. It is an error condition if the specified index is greater than the number of elements in the array.

Note that this operation will, in common use, contain a JSON Pointer that does not resolve to an existing value in the target document. As such, the pointer's error handling algorithm is 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 specified location in the target document.

Example:

{ "remove": "/a/b/c" }
             

If removing an element from an array, any elements above the specified index are shifted one position to the left.

It is an error condition if a value at the specified location does not exist.

4.3. replace

The "replace" operation replaces the value at the specified location in the target document with a new value. The operation object contains a "value" member that specifies the replacement value.

Example:

{ "replace": "/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.

It is an error condition if a value at the specified location does not exist.

4.4. move

The "move" operation removes the value at one location and adds it to another location in the target document.

The operation object contains 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.

Example:

{ "move": "/a/b/c", "to": "/a/b/d" }
             

This operation is functionally identical to expressing a "remove" operation, followed immediately by an "add" operation at the new location with the value that was just removed. Moving a value to its current location can be safely ignored.

If the location in the "to" member references a member of an existing object in the target document, it is an error condition if a value at the specified location already exists (unless "move" 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. It is an error condition if the specified index is greater than the number of elements in the array.

4.5. copy

The "copy" operation copies the value at one location to another location in the target document.

The operation object contains 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.

Example:

{ "copy": "/a/b/c", "to": "/a/b/e" }
             

If the location in the "to" member references a member of an existing object in the target document, it is an error condition if a value at the specified location already exists.

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. It is an error condition if the specified index is greater than the number of elements in the array.

4.6. test

The "test" operation tests that a value at the specified location in the target document is equal to a specified value. The operation object contains a "value" member that specifies the value to test for. If values are or contain objects or arrays, they must be identical (i.e. same order of elements, with the same values).

Example:

{ "test": "/a/b/c", "value": "foo" }
             

It is an error condition if the value at the specified location is not equal to the specified value.

5. Error Handling

If an error condition occurs, evaluation of the JSON Patch document SHOULD terminate and application of the entire patch document SHALL NOT be deemed successful.

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, Julian Reschke, 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:

[
    { "add": "/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:

[
    { "add": "/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:

[
    { "remove": "/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:

[
    { "remove": "/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:

[
      { "replace": "/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:

[
    { "move": "/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:

[
    { "move": "/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:

[
    { "test": "/baz", "value": "qux" },
    { "test": "/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:

[
    { "test": "/baz", "value": "bar" }
]
                 

Authors' Addresses