gjson常用使用方法

1、包路径：github.com/tidwall/gjson/（直接可以看这个链接，打开很慢，所以备份下）

2、获取单个标签值：

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())
}

输出结果:Prichard

3、路径匹配：

json数据

{
  "name": {"first": "Tom", "last": "Anderson"},
  "age":37,
  "children": ["Sara","Alex","Jack"],
  "fav.movie": "Deer Hunter",
  "friends": [
    {"first": "Dale", "last": "Murphy", "age": 44},
    {"first": "Roger", "last": "Craig", "age": 68},
    {"first": "Jane", "last": "Murphy", "age": 47}
  ]
}

匹配结果：

"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"

friends.#[last=="Murphy"].first    >> "Dale"
friends.#[last=="Murphy"]#.first   >> ["Dale","Jane"]
friends.#[age>45]#.last            >> ["Craig","Murphy"]
friends.#[first%"D*"].last         >> "Murphy"

json数据： 

{"name": "Gilbert", "age": 61}
{"name": "Alexa", "age": 34}
{"name": "May", "age": 57}
{"name": "Deloise", "age": 44}

匹配结果： 

..#                   >> 4
..1                   >> {"name": "Alexa", "age": 34}
..3                   >> {"name": "Deloise", "age": 44}
..#.name              >> ["Gilbert","Alexa","May","Deloise"]
..#[name="May"].age   >> 57

 4、获取嵌套数组值：

{
  "programmers": [
    {
      "firstName": "Janet", 
      "lastName": "McLaughlin", 
    }, {
      "firstName": "Elliotte", 
      "lastName": "Hunter", 
    }, {
      "firstName": "Jason", 
      "lastName": "Harold", 
    }
  ]
}

result := gjson.Get(json, "programmers.#.lastName")
for _, name := range result.Array() {
	println(name.String())
}

name := gjson.Get(json, `programmers.#[lastName="Hunter"].firstName`)
println(name.String())  // prints "Elliotte"

result := gjson.Get(json, "programmers")
result.ForEach(func(key, value gjson.Result) bool {
	println(value.String()) 
	return true // keep iterating
})

5、判断某个值是否存在：

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")
}

6、验证json格式

if !gjson.Valid(json) {
	return errors.New("invalid json")
}
value := gjson.Get(json, "name.last")