Astjson requires at least go1.18 as it uses some features from reflect library.
go get github.com/xieyuschen/astjsonpackage main
import (
"errors"
"fmt"
"github.com/xieyuschen/astjson"
)
const (
jsonStr = `
{
"num": 999,
"str": "helloworld",
"enabled": true ,
"sub1": {
"sub2": {
"key": 999
}
},
"name": "astjson"
}`
)
type (
Sub1 struct {
Sub2 Sub2 `json:"sub2"`
}
Sub2 struct {
Key int `json:"key"`
}
demo struct {
Num int `json:"num"`
Str string `json:"str"`
Enabled bool `json:"enabled"`
Sub Sub1 `json:"sub1"`
}
)
func main() {
astValue := astjson.NewParser([]byte(jsonStr)).Parse()
val, err := astjson.NewWalker(astValue).
// field "str" is required
Field("str").
// field "num" is optional, but if it exists the validator will be triggered
Optional("num", equal999).
Field("enabled").Validate(isTrue).
Path("sub1").Path("sub2").Validate(equal999).EndPath().
ValidateKey("name", hasAstjsonName).
Walk()
if err != nil {
panic(err)
}
var d demo
_ = astjson.NewDecoder().Unmarshal(val, &d)
fmt.Println(d)
}
func equal999(value *astjson.Value) error {
actual := value.AstValue.(astjson.NumberAst).GetInt64()
if actual == 999 {
return nil
}
return errors.New("num should be 999")
}
func isTrue(value *astjson.Value) error {
if bool(value.AstValue.(astjson.BoolAst)) {
return nil
}
return errors.New("bool should be true")
}
func hasAstjsonName(value *astjson.Value) error {
if value.AstValue.(astjson.StringAst) == "astjson" {
return nil
}
return errors.New("name should be astjson")
}See more examples here.
Haskell json library aeson parsed AST first in its early version as a default way. However, it skips to convert AST first to speed up parsing as a new default way.
Parsing AST first is slower than directly parsing json, however, it provides more flexibilities. Hence, inspired by aeson, I wrote a ast json to help parsing json to AST.