279 lines
6.9 KiB
Markdown
279 lines
6.9 KiB
Markdown
<p align="center">
|
|
<img
|
|
src="logo.png"
|
|
width="240" height="78" border="0" alt="GJSON">
|
|
<br>
|
|
<a href="https://travis-ci.org/tidwall/gjson"><img src="https://img.shields.io/travis/tidwall/gjson.svg?style=flat-square" alt="Build Status"></a><!--
|
|
<a href="http://gocover.io/github.com/tidwall/gjson"><img src="https://img.shields.io/badge/coverage-97%25-brightgreen.svg?style=flat-square" alt="Code Coverage"></a>
|
|
-->
|
|
<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>
|
|
</p>
|
|
|
|
<p align="center">get a json value quickly</a></p>
|
|
|
|
GJSON is a Go package the provides a [very fast](#performance) and simple way to get a value from a json document. The reason for this library it to give efficient json indexing for the [BuntDB](https://github.com/tidwall/buntdb) project.
|
|
|
|
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". This function expects that the json is well-formed and validates. Invalid json will not panic, but it may return back unexpected results. 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
|
|
```
|
|
|
|
## Path Syntax
|
|
|
|
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": "James", "last": "Murphy"},
|
|
{"first": "Roger", "last": "Craig"}
|
|
]
|
|
}
|
|
```
|
|
```
|
|
"name.last" >> "Anderson"
|
|
"age" >> 37
|
|
"children.#" >> 3
|
|
"children.1" >> "Alex"
|
|
"child*.2" >> "Jack"
|
|
"c?ildren.0" >> "Sara"
|
|
"fav\.movie" >> "Deer Hunter"
|
|
"friends.#.first" >> [ "James", "Roger" ]
|
|
"friends.1.last" >> "Craig"
|
|
```
|
|
To query an array:
|
|
```
|
|
`friends.#[last="Murphy"].first` >> "James"
|
|
```
|
|
|
|
## 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.Multi // holds nested array values
|
|
```
|
|
|
|
There are a variety of handy functions that work on a result:
|
|
|
|
```go
|
|
result.Value() interface{}
|
|
result.Int() int64
|
|
result.Float() float64
|
|
result.String() string
|
|
result.Bool() bool
|
|
result.Array() []gjson.Result
|
|
result.Map() map[string]gjson.Result
|
|
result.Get(path string) Result
|
|
```
|
|
|
|
The `result.Value()` function returns an `interface{}` which requires type assertion and is one of the following Go types:
|
|
|
|
```go
|
|
boolean >> bool
|
|
number >> float64
|
|
string >> string
|
|
null >> nil
|
|
array >> []interface{}
|
|
object >> map[string]interface{}
|
|
```
|
|
|
|
## 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"
|
|
```
|
|
|
|
|
|
## 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 you 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")
|
|
}
|
|
```
|
|
|
|
## 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
|
|
}
|
|
```
|
|
|
|
## 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),
|
|
and [jsonparser](https://github.com/buger/jsonparser)
|
|
|
|
```
|
|
BenchmarkGJSONGet-8 15000000 333 ns/op 0 B/op 0 allocs/op
|
|
BenchmarkGJSONUnmarshalMap-8 900000 4188 ns/op 1920 B/op 26 allocs/op
|
|
BenchmarkJSONUnmarshalMap-8 600000 8908 ns/op 3048 B/op 69 allocs/op
|
|
BenchmarkJSONUnmarshalStruct-8 600000 9026 ns/op 1832 B/op 69 allocs/op
|
|
BenchmarkJSONDecoder-8 300000 14339 ns/op 4224 B/op 184 allocs/op
|
|
BenchmarkFFJSONLexer-8 1500000 3156 ns/op 896 B/op 8 allocs/op
|
|
BenchmarkEasyJSONLexer-8 3000000 938 ns/op 613 B/op 6 allocs/op
|
|
BenchmarkJSONParserGet-8 3000000 442 ns/op 21 B/op 0 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 though 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 1.7.*
|
|
|
|
## Contact
|
|
Josh Baker [@tidwall](http://twitter.com/tidwall)
|
|
|
|
## License
|
|
|
|
GJSON source code is available under the MIT [License](/LICENSE).
|