GJSON is a Go package that provides a fast and simple way to get values from a json document.
It has features such as one line retrieval, dot notation paths, iteration, and parsing json lines.
Also check out SJSON for modifying json, and the JJ command line tool.
Getting Started
Installing
To start using GJSON, install Go and run go get:
$ 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.
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 function to get multiple values at once, and GetBytes 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.
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 '\'.
{
"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. 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:
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:
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.
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.
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