json格式還是現今web服務最常用的數據交換格式，有時需要對其字段進行篩選過濾和重組。
在github搜索，沒有發現合適的，於是自己寫了一個開源：https://github.com/sdghchj/rules_engine。
實現主過程要用到了go標準庫中的詞法分析包token和抽象語法樹包ast，略。
Example
Use rule engine by sql,only ‘select … from … where …’
eng := NewJsonEngine(true)
//sql keyword'case ingnored
err := eng.ParseSql(`select "3" as a.a,'hello' as a.b,Sum(b.c) as a.c,Substr(c,2) as a.d,currenttimestamp() as a.e,* as a.f,b.f,b.c,b.c[2] + b.c[3] as b.b from aaa where a < 2 and b.c[4] = 5 and e.f = 2`)
if err != nil {
fmt.Println(err)
}
text := `{"a":1,"b":{"c":[1,2,3,4,5]},"c":"123456789","e":{"f":2}}`
jsonText, err := eng.Convert("aaa",text)
if err != nil {
fmt.Println(err)
}
fmt.Println(string(jsonText))
/*output
{
"a": {
"a": "3",
"b": "hello",
"c": 15,
"d": "3456",
"e": 1556693661,
"f": {
"a": 1,
"b": {
"c": [
1,
2,
3,
4,
5
]
},
"c": "123456789",
"e": {
"f": 2
}
}
},
"b": {
"b": 7,
"c": [
1,
2,
3,
4,
5
]
}
}*/
text = `{"a":5,"b":{"c":[6,5,4,3,2,1]},"c":"987654321"}`
jsonText, err = eng.Convert("aaa",text)
if err != nil {
fmt.Println(err)
}
fmt.Println(string(jsonText)) // null
Use rule
rule := rule.NewJsonRule(true)
//query
fieldFilter := filter.NewFieldFilter()
fieldFilter.Parse("a < 2 && b.c[4] == 5 && e.f == 2")
rule.AddConverter(fieldFilter)
m := mapper.NewMapper()
//select fields
m.AddField("3", "a.a")
m.AddField("'hello'", "a.b")
m.AddField("Sum(b.c)", "a.c")
m.AddField("Substr(c,2)", "a.d")
m.AddCurrentTimestampField("a.e", nil)
m.AddField("*", "a.f")
m.AddField("b.c", "")
m.AddField("b.c[2] + b.c[3]", "b.a")
m.AddField("CurrentTimestamp()", "b.b")
rule.AddConverter(m)
text := `
{
"a":1,
"b":{
"c":[1,2,3,4,5]
},
"c":"123456789",
"e":{
"f":2
}
}
`
jsonText, _ := rule.Convert(text)
fmt.Println(string(jsonText))
/*
//output:
{
"a": {
"a": 3,
"b": "hello",
"c": 15,
"d": "3456789",
"e": 1556611910,
"f": {
"a": 1,
"b": {
"c": [
1,
2,
3,
4,
5
]
},
"c": "123456789",
"e": {
"f": 2
}
}
},
"b": {
"a": 7,
"b": 1556611910,
"c": [
1,
2,
3,
4,
5
]
}
}
*/
tm := time.Now()
for i := 0; i < 10000; i ++ {
_,_ = rule.Convert(text)
}
fmt.Println( "time elapse:",time.Now().Sub(tm).Nanoseconds(),"ns")
/*
//output:
time elapse: 4265625000 ns
*/
Supported golang operators
+ - * / % && || ! > < == >= <= & | >> << [index]
Supported other operators in sql
= as ==
and as &&
or as ||
not as !
Supported functions (ignore case)
- sum(array)
- average(array)
- len(array)
- substr(text,pos,length)
- currenttimestamp()
- regex(text,pattern)
- in(value,array)
- abs(number)
- exp(number)
- sqrt(number)
- power(numberX,numberY)
- ceil(number)
- floor(number)
- iif(condition,whenTrue,whenFalse)