JSON-Patch
jsonpatch
is a library which provides functionality for both applying
RFC6902 JSON patches against documents, as
well as for calculating & applying RFC7396 JSON merge patches.
Get It!
Latest and greatest:
go get -u github.com/evanphx/json-patch/v5
Stable Versions:
- Version 5:
go get -u gopkg.in/evanphx/json-patch.v5
- Version 4:
go get -u gopkg.in/evanphx/json-patch.v4
(previous versions below v3
are unavailable)
Use It!
Configuration
-
There is a global configuration variable jsonpatch.SupportNegativeIndices
.
This defaults to true
and enables the non-standard practice of allowing
negative indices to mean indices starting at the end of an array. This
functionality can be disabled by setting jsonpatch.SupportNegativeIndices = false
.
-
There is a global configuration variable jsonpatch.AccumulatedCopySizeLimit
,
which limits the total size increase in bytes caused by "copy" operations in a
patch. It defaults to 0, which means there is no limit.
These global variables control the behavior of jsonpatch.Apply
.
An alternative to jsonpatch.Apply
is jsonpatch.ApplyWithOptions
whose behavior
is controlled by an options
parameter of type *jsonpatch.ApplyOptions
.
Structure jsonpatch.ApplyOptions
includes the configuration options above
and adds two new options: AllowMissingPathOnRemove
and EnsurePathExistsOnAdd
.
When AllowMissingPathOnRemove
is set to true
, jsonpatch.ApplyWithOptions
will ignore
remove
operations whose path
points to a non-existent location in the JSON document.
AllowMissingPathOnRemove
defaults to false
which will lead to jsonpatch.ApplyWithOptions
returning an error when hitting a missing path
on remove
.
When EnsurePathExistsOnAdd
is set to true
, jsonpatch.ApplyWithOptions
will make sure
that add
operations produce all the path
elements that are missing from the target object.
Use jsonpatch.NewApplyOptions
to create an instance of jsonpatch.ApplyOptions
whose values are populated from the global configuration variables.
Create and apply a merge patch
Given both an original JSON document and a modified JSON document, you can create
a Merge Patch document.
It can describe the changes needed to convert from the original to the
modified JSON document.
Once you have a merge patch, you can apply it to other JSON documents using the
jsonpatch.MergePatch(document, patch)
function.
package main
import (
"fmt"
jsonpatch "github.com/evanphx/json-patch"
)
func main() {
// Let's create a merge patch from these two documents...
original := []byte(`{"name": "John", "age": 24, "height": 3.21}`)
target := []byte(`{"name": "Jane", "age": 24}`)
patch, err := jsonpatch.CreateMergePatch(original, target)
if err != nil {
panic(err)
}
// Now lets apply the patch against a different JSON document...
alternative := []byte(`{"name": "Tina", "age": 28, "height": 3.75}`)
modifiedAlternative, err := jsonpatch.MergePatch(alternative, patch)
fmt.Printf("patch document: %s\n", patch)
fmt.Printf("updated alternative doc: %s\n", modifiedAlternative)
}
When ran, you get the following output:
$ go run main.go
patch document: {"height":null,"name":"Jane"}
updated alternative doc: {"age":28,"name":"Jane"}
Create and apply a JSON Patch
You can create patch objects using DecodePatch([]byte)
, which can then
be applied against JSON documents.
The following is an example of creating a patch from two operations, and
applying it against a JSON document.
package main
import (
"fmt"
jsonpatch "github.com/evanphx/json-patch"
)
func main() {
original := []byte(`{"name": "John", "age": 24, "height": 3.21}`)
patchJSON := []byte(`[
{"op": "replace", "path": "/name", "value": "Jane"},
{"op": "remove", "path": "/height"}
]`)
patch, err := jsonpatch.DecodePatch(patchJSON)
if err != nil {
panic(err)
}
modified, err := patch.Apply(original)
if err != nil {
panic(err)
}
fmt.Printf("Original document: %s\n", original)
fmt.Printf("Modified document: %s\n", modified)
}
When ran, you get the following output:
$ go run main.go
Original document: {"name": "John", "age": 24, "height": 3.21}
Modified document: {"age":24,"name":"Jane"}
Comparing JSON documents
Due to potential whitespace and ordering differences, one cannot simply compare
JSON strings or byte-arrays directly.
As such, you can instead use jsonpatch.Equal(document1, document2)
to
determine if two JSON documents are structurally equal. This ignores
whitespace differences, and key-value ordering.
package main
import (
"fmt"
jsonpatch "github.com/evanphx/json-patch"
)
func main() {
original := []byte(`{"name": "John", "age": 24, "height": 3.21}`)
similar := []byte(`
{
"age": 24,
"height": 3.21,
"name": "John"
}
`)
different := []byte(`{"name": "Jane", "age": 20, "height": 3.37}`)
if jsonpatch.Equal(original, similar) {
fmt.Println(`"original" is structurally equal to "similar"`)
}
if !jsonpatch.Equal(original, different) {
fmt.Println(`"original" is _not_ structurally equal to "different"`)
}
}
When ran, you get the following output:
$ go run main.go
"original" is structurally equal to "similar"
"original" is _not_ structurally equal to "different"
Combine merge patches
Given two JSON merge patch documents, it is possible to combine them into a
single merge patch which can describe both set of changes.
The resulting merge patch can be used such that applying it results in a
document structurally similar as merging each merge patch to the document
in succession.
package main
import (
"fmt"
jsonpatch "github.com/evanphx/json-patch"
)
func main() {
original := []byte(`{"name": "John", "age": 24, "height": 3.21}`)
nameAndHeight := []byte(`{"height":null,"name":"Jane"}`)
ageAndEyes := []byte(`{"age":4.23,"eyes":"blue"}`)
// Let's combine these merge patch documents...
combinedPatch, err := jsonpatch.MergeMergePatches(nameAndHeight, ageAndEyes)
if err != nil {
panic(err)
}
// Apply each patch individual against the original document
withoutCombinedPatch, err := jsonpatch.MergePatch(original, nameAndHeight)
if err != nil {
panic(err)
}
withoutCombinedPatch, err = jsonpatch.MergePatch(withoutCombinedPatch, ageAndEyes)
if err != nil {
panic(err)
}
// Apply the combined patch against the original document
withCombinedPatch, err := jsonpatch.MergePatch(original, combinedPatch)
if err != nil {
panic(err)
}
// Do both result in the same thing? They should!
if jsonpatch.Equal(withCombinedPatch, withoutCombinedPatch) {
fmt.Println("Both JSON documents are structurally the same!")
}
fmt.Printf("combined merge patch: %s", combinedPatch)
}
When ran, you get the following output:
$ go run main.go
Both JSON documents are structurally the same!
combined merge patch: {"age":4.23,"eyes":"blue","height":null,"name":"Jane"}
CLI for comparing JSON documents
You can install the commandline program json-patch
.
This program can take multiple JSON patch documents as arguments,
and fed a JSON document from stdin
. It will apply the patch(es) against
the document and output the modified doc.
patch.1.json
[
{"op": "replace", "path": "/name", "value": "Jane"},
{"op": "remove", "path": "/height"}
]
patch.2.json
[
{"op": "add", "path": "/address", "value": "123 Main St"},
{"op": "replace", "path": "/age", "value": "21"}
]
document.json
{
"name": "John",
"age": 24,
"height": 3.21
}
You can then run:
$ go install github.com/evanphx/json-patch/cmd/json-patch
$ cat document.json | json-patch -p patch.1.json -p patch.2.json
{"address":"123 Main St","age":"21","name":"Jane"}
Help It!
Contributions are welcomed! Leave an issue
or create a PR.
Before creating a pull request, we'd ask that you make sure tests are passing
and that you have added new tests when applicable.
Contributors can run tests using:
go test -cover ./...
Builds for pull requests are tested automatically
using TravisCI.