493 lines
14 KiB
Markdown
493 lines
14 KiB
Markdown
|
<p align="center">
|
||
|
<img
|
||
|
src="logo.png"
|
||
|
width="240" height="78" border="0" alt="GJSON">
|
||
|
<br>
|
||
|
<a href="https://godoc.org/github.com/tidwall/gjson"><img src="https://img.shields.io/badge/api-reference-blue.svg?style=flat-square" alt="GoDoc"></a>
|
||
|
<a href="http://tidwall.com/gjson-play"><img src="https://img.shields.io/badge/%F0%9F%8F%90-playground-9900cc.svg?style=flat-square" alt="GJSON Playground"></a>
|
||
|
</p>
|
||
|
|
||
|
<p align="center">get json values quickly</a></p>
|
||
|
|
||
|
GJSON is a Go package that provides a [fast](#performance) and [simple](#get-a-value) way to get values from a json document.
|
||
|
It has features such as [one line retrieval](#get-a-value), [dot notation paths](#path-syntax), [iteration](#iterate-through-an-object-or-array), and [parsing json lines](#json-lines).
|
||
|
|
||
|
Also check out [SJSON](https://github.com/tidwall/sjson) for modifying json, and the [JJ](https://github.com/tidwall/jj) command line tool.
|
||
|
|
||
|
Getting Started
|
||
|
===============
|
||
|
|
||
|
## Installing
|
||
|
|
||
|
To start using GJSON, install Go and run `go get`:
|
||
|
|
||
|
```sh
|
||
|
$ go get -u github.com/tidwall/gjson
|
||
|
```
|
||
|
|
||
|
This will retrieve the library.
|
||
|
|
||
|
## Get a value
|
||
|
Get searches json for the specified path. A path is in dot syntax, such as "name.last" or "age". When the value is found it's returned immediately.
|
||
|
|
||
|
```go
|
||
|
package main
|
||
|
|
||
|
import "github.com/tidwall/gjson"
|
||
|
|
||
|
const json = `{"name":{"first":"Janet","last":"Prichard"},"age":47}`
|
||
|
|
||
|
func main() {
|
||
|
value := gjson.Get(json, "name.last")
|
||
|
println(value.String())
|
||
|
}
|
||
|
```
|
||
|
|
||
|
This will print:
|
||
|
|
||
|
```
|
||
|
Prichard
|
||
|
```
|
||
|
*There's also the [GetMany](#get-multiple-values-at-once) function to get multiple values at once, and [GetBytes](#working-with-bytes) for working with JSON byte slices.*
|
||
|
|
||
|
## Path Syntax
|
||
|
|
||
|
Below is a quick overview of the path syntax, for more complete information please
|
||
|
check out [GJSON Syntax](SYNTAX.md).
|
||
|
|
||
|
A path is a series of keys separated by a dot.
|
||
|
A key may contain special wildcard characters '\*' and '?'.
|
||
|
To access an array value use the index as the key.
|
||
|
To get the number of elements in an array or to access a child path, use the '#' character.
|
||
|
The dot and wildcard characters can be escaped with '\\'.
|
||
|
|
||
|
```json
|
||
|
{
|
||
|
"name": {"first": "Tom", "last": "Anderson"},
|
||
|
"age":37,
|
||
|
"children": ["Sara","Alex","Jack"],
|
||
|
"fav.movie": "Deer Hunter",
|
||
|
"friends": [
|
||
|
{"first": "Dale", "last": "Murphy", "age": 44, "nets": ["ig", "fb", "tw"]},
|
||
|
{"first": "Roger", "last": "Craig", "age": 68, "nets": ["fb", "tw"]},
|
||
|
{"first": "Jane", "last": "Murphy", "age": 47, "nets": ["ig", "tw"]}
|
||
|
]
|
||
|
}
|
||
|
```
|
||
|
```
|
||
|
"name.last" >> "Anderson"
|
||
|
"age" >> 37
|
||
|
"children" >> ["Sara","Alex","Jack"]
|
||
|
"children.#" >> 3
|
||
|
"children.1" >> "Alex"
|
||
|
"child*.2" >> "Jack"
|
||
|
"c?ildren.0" >> "Sara"
|
||
|
"fav\.movie" >> "Deer Hunter"
|
||
|
"friends.#.first" >> ["Dale","Roger","Jane"]
|
||
|
"friends.1.last" >> "Craig"
|
||
|
```
|
||
|
|
||
|
You can also query an array for the first match by using `#(...)`, or find all
|
||
|
matches with `#(...)#`. Queries support the `==`, `!=`, `<`, `<=`, `>`, `>=`
|
||
|
comparison operators and the simple pattern matching `%` (like) and `!%`
|
||
|
(not like) operators.
|
||
|
|
||
|
```
|
||
|
friends.#(last=="Murphy").first >> "Dale"
|
||
|
friends.#(last=="Murphy")#.first >> ["Dale","Jane"]
|
||
|
friends.#(age>45)#.last >> ["Craig","Murphy"]
|
||
|
friends.#(first%"D*").last >> "Murphy"
|
||
|
friends.#(first!%"D*").last >> "Craig"
|
||
|
friends.#(nets.#(=="fb"))#.first >> ["Dale","Roger"]
|
||
|
```
|
||
|
|
||
|
*Please note that prior to v1.3.0, queries used the `#[...]` brackets. This was
|
||
|
changed in v1.3.0 as to avoid confusion with the new
|
||
|
[multipath](SYNTAX.md#multipaths) syntax. For backwards compatibility,
|
||
|
`#[...]` will continue to work until the next major release.*
|
||
|
|
||
|
## Result Type
|
||
|
|
||
|
GJSON supports the json types `string`, `number`, `bool`, and `null`.
|
||
|
Arrays and Objects are returned as their raw json types.
|
||
|
|
||
|
The `Result` type holds one of these:
|
||
|
|
||
|
```
|
||
|
bool, for JSON booleans
|
||
|
float64, for JSON numbers
|
||
|
string, for JSON string literals
|
||
|
nil, for JSON null
|
||
|
```
|
||
|
|
||
|
To directly access the value:
|
||
|
|
||
|
```go
|
||
|
result.Type // can be String, Number, True, False, Null, or JSON
|
||
|
result.Str // holds the string
|
||
|
result.Num // holds the float64 number
|
||
|
result.Raw // holds the raw json
|
||
|
result.Index // index of raw value in original json, zero means index unknown
|
||
|
```
|
||
|
|
||
|
There are a variety of handy functions that work on a result:
|
||
|
|
||
|
```go
|
||
|
result.Exists() bool
|
||
|
result.Value() interface{}
|
||
|
result.Int() int64
|
||
|
result.Uint() uint64
|
||
|
result.Float() float64
|
||
|
result.String() string
|
||
|
result.Bool() bool
|
||
|
result.Time() time.Time
|
||
|
result.Array() []gjson.Result
|
||
|
result.Map() map[string]gjson.Result
|
||
|
result.Get(path string) Result
|
||
|
result.ForEach(iterator func(key, value Result) bool)
|
||
|
result.Less(token Result, caseSensitive bool) bool
|
||
|
```
|
||
|
|
||
|
The `result.Value()` function returns an `interface{}` which requires type assertion and is one of the following Go types:
|
||
|
|
||
|
The `result.Array()` function returns back an array of values.
|
||
|
If the result represents a non-existent value, then an empty array will be returned.
|
||
|
If the result is not a JSON array, the return value will be an array containing one result.
|
||
|
|
||
|
```go
|
||
|
boolean >> bool
|
||
|
number >> float64
|
||
|
string >> string
|
||
|
null >> nil
|
||
|
array >> []interface{}
|
||
|
object >> map[string]interface{}
|
||
|
```
|
||
|
|
||
|
### 64-bit integers
|
||
|
|
||
|
The `result.Int()` and `result.Uint()` calls are capable of reading all 64 bits, allowing for large JSON integers.
|
||
|
|
||
|
```go
|
||
|
result.Int() int64 // -9223372036854775808 to 9223372036854775807
|
||
|
result.Uint() int64 // 0 to 18446744073709551615
|
||
|
```
|
||
|
|
||
|
## Modifiers and path chaining
|
||
|
|
||
|
New in version 1.2 is support for modifier functions and path chaining.
|
||
|
|
||
|
A modifier is a path component that performs custom processing on the
|
||
|
json.
|
||
|
|
||
|
Multiple paths can be "chained" together using the pipe character.
|
||
|
This is useful for getting results from a modified query.
|
||
|
|
||
|
For example, using the built-in `@reverse` modifier on the above json document,
|
||
|
we'll get `children` array and reverse the order:
|
||
|
|
||
|
```
|
||
|
"children|@reverse" >> ["Jack","Alex","Sara"]
|
||
|
"children|@reverse|0" >> "Jack"
|
||
|
```
|
||
|
|
||
|
There are currently the following built-in modifiers:
|
||
|
|
||
|
- `@reverse`: Reverse an array or the members of an object.
|
||
|
- `@ugly`: Remove all whitespace from a json document.
|
||
|
- `@pretty`: Make the json document more human readable.
|
||
|
- `@this`: Returns the current element. It can be used to retrieve the root element.
|
||
|
- `@valid`: Ensure the json document is valid.
|
||
|
- `@flatten`: Flattens an array.
|
||
|
- `@join`: Joins multiple objects into a single object.
|
||
|
|
||
|
### Modifier arguments
|
||
|
|
||
|
A modifier may accept an optional argument. The argument can be a valid JSON
|
||
|
document or just characters.
|
||
|
|
||
|
For example, the `@pretty` modifier takes a json object as its argument.
|
||
|
|
||
|
```
|
||
|
@pretty:{"sortKeys":true}
|
||
|
```
|
||
|
|
||
|
Which makes the json pretty and orders all of its keys.
|
||
|
|
||
|
```json
|
||
|
{
|
||
|
"age":37,
|
||
|
"children": ["Sara","Alex","Jack"],
|
||
|
"fav.movie": "Deer Hunter",
|
||
|
"friends": [
|
||
|
{"age": 44, "first": "Dale", "last": "Murphy"},
|
||
|
{"age": 68, "first": "Roger", "last": "Craig"},
|
||
|
{"age": 47, "first": "Jane", "last": "Murphy"}
|
||
|
],
|
||
|
"name": {"first": "Tom", "last": "Anderson"}
|
||
|
}
|
||
|
```
|
||
|
|
||
|
*The full list of `@pretty` options are `sortKeys`, `indent`, `prefix`, and `width`.
|
||
|
Please see [Pretty Options](https://github.com/tidwall/pretty#customized-output) for more information.*
|
||
|
|
||
|
### Custom modifiers
|
||
|
|
||
|
You can also add custom modifiers.
|
||
|
|
||
|
For example, here we create a modifier that makes the entire json document upper
|
||
|
or lower case.
|
||
|
|
||
|
```go
|
||
|
gjson.AddModifier("case", func(json, arg string) string {
|
||
|
if arg == "upper" {
|
||
|
return strings.ToUpper(json)
|
||
|
}
|
||
|
if arg == "lower" {
|
||
|
return strings.ToLower(json)
|
||
|
}
|
||
|
return json
|
||
|
})
|
||
|
```
|
||
|
|
||
|
```
|
||
|
"children|@case:upper" >> ["SARA","ALEX","JACK"]
|
||
|
"children|@case:lower|@reverse" >> ["jack","alex","sara"]
|
||
|
```
|
||
|
|
||
|
## JSON Lines
|
||
|
|
||
|
There's support for [JSON Lines](http://jsonlines.org/) using the `..` prefix, which treats a multilined document as an array.
|
||
|
|
||
|
For example:
|
||
|
|
||
|
```
|
||
|
{"name": "Gilbert", "age": 61}
|
||
|
{"name": "Alexa", "age": 34}
|
||
|
{"name": "May", "age": 57}
|
||
|
{"name": "Deloise", "age": 44}
|
||
|
```
|
||
|
|
||
|
```
|
||
|
..# >> 4
|
||
|
..1 >> {"name": "Alexa", "age": 34}
|
||
|
..3 >> {"name": "Deloise", "age": 44}
|
||
|
..#.name >> ["Gilbert","Alexa","May","Deloise"]
|
||
|
..#(name="May").age >> 57
|
||
|
```
|
||
|
|
||
|
The `ForEachLines` function will iterate through JSON lines.
|
||
|
|
||
|
```go
|
||
|
gjson.ForEachLine(json, func(line gjson.Result) bool{
|
||
|
println(line.String())
|
||
|
return true
|
||
|
})
|
||
|
```
|
||
|
|
||
|
## Get nested array values
|
||
|
|
||
|
Suppose you want all the last names from the following json:
|
||
|
|
||
|
```json
|
||
|
{
|
||
|
"programmers": [
|
||
|
{
|
||
|
"firstName": "Janet",
|
||
|
"lastName": "McLaughlin",
|
||
|
}, {
|
||
|
"firstName": "Elliotte",
|
||
|
"lastName": "Hunter",
|
||
|
}, {
|
||
|
"firstName": "Jason",
|
||
|
"lastName": "Harold",
|
||
|
}
|
||
|
]
|
||
|
}
|
||
|
```
|
||
|
|
||
|
You would use the path "programmers.#.lastName" like such:
|
||
|
|
||
|
```go
|
||
|
result := gjson.Get(json, "programmers.#.lastName")
|
||
|
for _, name := range result.Array() {
|
||
|
println(name.String())
|
||
|
}
|
||
|
```
|
||
|
|
||
|
You can also query an object inside an array:
|
||
|
|
||
|
```go
|
||
|
name := gjson.Get(json, `programmers.#(lastName="Hunter").firstName`)
|
||
|
println(name.String()) // prints "Elliotte"
|
||
|
```
|
||
|
|
||
|
## Iterate through an object or array
|
||
|
|
||
|
The `ForEach` function allows for quickly iterating through an object or array.
|
||
|
The key and value are passed to the iterator function for objects.
|
||
|
Only the value is passed for arrays.
|
||
|
Returning `false` from an iterator will stop iteration.
|
||
|
|
||
|
```go
|
||
|
result := gjson.Get(json, "programmers")
|
||
|
result.ForEach(func(key, value gjson.Result) bool {
|
||
|
println(value.String())
|
||
|
return true // keep iterating
|
||
|
})
|
||
|
```
|
||
|
|
||
|
## Simple Parse and Get
|
||
|
|
||
|
There's a `Parse(json)` function that will do a simple parse, and `result.Get(path)` that will search a result.
|
||
|
|
||
|
For example, all of these will return the same result:
|
||
|
|
||
|
```go
|
||
|
gjson.Parse(json).Get("name").Get("last")
|
||
|
gjson.Get(json, "name").Get("last")
|
||
|
gjson.Get(json, "name.last")
|
||
|
```
|
||
|
|
||
|
## Check for the existence of a value
|
||
|
|
||
|
Sometimes you just want to know if a value exists.
|
||
|
|
||
|
```go
|
||
|
value := gjson.Get(json, "name.last")
|
||
|
if !value.Exists() {
|
||
|
println("no last name")
|
||
|
} else {
|
||
|
println(value.String())
|
||
|
}
|
||
|
|
||
|
// Or as one step
|
||
|
if gjson.Get(json, "name.last").Exists() {
|
||
|
println("has a last name")
|
||
|
}
|
||
|
```
|
||
|
|
||
|
## Validate JSON
|
||
|
|
||
|
The `Get*` and `Parse*` functions expects that the json is well-formed. Bad json will not panic, but it may return back unexpected results.
|
||
|
|
||
|
If you are consuming JSON from an unpredictable source then you may want to validate prior to using GJSON.
|
||
|
|
||
|
```go
|
||
|
if !gjson.Valid(json) {
|
||
|
return errors.New("invalid json")
|
||
|
}
|
||
|
value := gjson.Get(json, "name.last")
|
||
|
```
|
||
|
|
||
|
## Unmarshal to a map
|
||
|
|
||
|
To unmarshal to a `map[string]interface{}`:
|
||
|
|
||
|
```go
|
||
|
m, ok := gjson.Parse(json).Value().(map[string]interface{})
|
||
|
if !ok {
|
||
|
// not a map
|
||
|
}
|
||
|
```
|
||
|
|
||
|
## Working with Bytes
|
||
|
|
||
|
If your JSON is contained in a `[]byte` slice, there's the [GetBytes](https://godoc.org/github.com/tidwall/gjson#GetBytes) function. This is preferred over `Get(string(data), path)`.
|
||
|
|
||
|
```go
|
||
|
var json []byte = ...
|
||
|
result := gjson.GetBytes(json, path)
|
||
|
```
|
||
|
|
||
|
If you are using the `gjson.GetBytes(json, path)` function and you want to avoid converting `result.Raw` to a `[]byte`, then you can use this pattern:
|
||
|
|
||
|
```go
|
||
|
var json []byte = ...
|
||
|
result := gjson.GetBytes(json, path)
|
||
|
var raw []byte
|
||
|
if result.Index > 0 {
|
||
|
raw = json[result.Index:result.Index+len(result.Raw)]
|
||
|
} else {
|
||
|
raw = []byte(result.Raw)
|
||
|
}
|
||
|
```
|
||
|
|
||
|
This is a best-effort no allocation sub slice of the original json. This method utilizes the `result.Index` field, which is the position of the raw data in the original json. It's possible that the value of `result.Index` equals zero, in which case the `result.Raw` is converted to a `[]byte`.
|
||
|
|
||
|
## Get multiple values at once
|
||
|
|
||
|
The `GetMany` function can be used to get multiple values at the same time.
|
||
|
|
||
|
```go
|
||
|
results := gjson.GetMany(json, "name.first", "name.last", "age")
|
||
|
```
|
||
|
|
||
|
The return value is a `[]Result`, which will always contain exactly the same number of items as the input paths.
|
||
|
|
||
|
## Performance
|
||
|
|
||
|
Benchmarks of GJSON alongside [encoding/json](https://golang.org/pkg/encoding/json/),
|
||
|
[ffjson](https://github.com/pquerna/ffjson),
|
||
|
[EasyJSON](https://github.com/mailru/easyjson),
|
||
|
[jsonparser](https://github.com/buger/jsonparser),
|
||
|
and [json-iterator](https://github.com/json-iterator/go)
|
||
|
|
||
|
```
|
||
|
BenchmarkGJSONGet-8 3000000 372 ns/op 0 B/op 0 allocs/op
|
||
|
BenchmarkGJSONUnmarshalMap-8 900000 4154 ns/op 1920 B/op 26 allocs/op
|
||
|
BenchmarkJSONUnmarshalMap-8 600000 9019 ns/op 3048 B/op 69 allocs/op
|
||
|
BenchmarkJSONDecoder-8 300000 14120 ns/op 4224 B/op 184 allocs/op
|
||
|
BenchmarkFFJSONLexer-8 1500000 3111 ns/op 896 B/op 8 allocs/op
|
||
|
BenchmarkEasyJSONLexer-8 3000000 887 ns/op 613 B/op 6 allocs/op
|
||
|
BenchmarkJSONParserGet-8 3000000 499 ns/op 21 B/op 0 allocs/op
|
||
|
BenchmarkJSONIterator-8 3000000 812 ns/op 544 B/op 9 allocs/op
|
||
|
```
|
||
|
|
||
|
JSON document used:
|
||
|
|
||
|
```json
|
||
|
{
|
||
|
"widget": {
|
||
|
"debug": "on",
|
||
|
"window": {
|
||
|
"title": "Sample Konfabulator Widget",
|
||
|
"name": "main_window",
|
||
|
"width": 500,
|
||
|
"height": 500
|
||
|
},
|
||
|
"image": {
|
||
|
"src": "Images/Sun.png",
|
||
|
"hOffset": 250,
|
||
|
"vOffset": 250,
|
||
|
"alignment": "center"
|
||
|
},
|
||
|
"text": {
|
||
|
"data": "Click Here",
|
||
|
"size": 36,
|
||
|
"style": "bold",
|
||
|
"vOffset": 100,
|
||
|
"alignment": "center",
|
||
|
"onMouseUp": "sun1.opacity = (sun1.opacity / 100) * 90;"
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
```
|
||
|
|
||
|
Each operation was rotated through one of the following search paths:
|
||
|
|
||
|
```
|
||
|
widget.window.name
|
||
|
widget.image.hOffset
|
||
|
widget.text.onMouseUp
|
||
|
```
|
||
|
|
||
|
*These benchmarks were run on a MacBook Pro 15" 2.8 GHz Intel Core i7 using Go 1.8 and can be found [here](https://github.com/tidwall/gjson-benchmarks).*
|
||
|
|
||
|
|
||
|
## Contact
|
||
|
Josh Baker [@tidwall](http://twitter.com/tidwall)
|
||
|
|
||
|
## License
|
||
|
|
||
|
GJSON source code is available under the MIT [License](/LICENSE).
|