go-json

JSON是一种受到广泛支持的语言格式，JSON里一个对象是一个字符串到值的映射，用花括号和逗号分隔，JSON在go里面可以被用来编写map和结构体，譬如

type Movie struct {
    Title  string
    Year   int  `json:"released"` //编码后名称变为released,不加默认用成员名
    Color  bool `json:"color,omitempty"`//编码后改名外加如果是空的那么不显示
    Actors []string
}

var movies = []Movie{
    {Title: "Casablanca", Year: 1942, Color: false,
        Actors: []string{"Humphrey Bogart", "Ingrid Bergman"}},
    {Title: "Cool Hand Luke", Year: 1967, Color: true,
        Actors: []string{"Paul Newman"}},
    {Title: "Bullitt", Year: 1968, Color: true,
        Actors: []string{"Steve McQueen", "Jacqueline Bisset"}},
    // ...
}

使用json.Marshal和json.MarshalIndent，前者返回一个slice，没有缩进，后者带两个参数，可以控制每一行的输出的前缀和每一段的缩进

data, err := json.MarshalIndent(movies, "", "    ")
if err != nil {
    log.Fatalf("JSON marshaling failed: %s", err)
}
fmt.Printf("%s\n", data)

输出

[
    {
        "Title": "Casablanca",
        "released": 1942,
        "Actors": [
            "Humphrey Bogart",
            "Ingrid Bergman"
        ]
    },
    {
        "Title": "Cool Hand Luke",
        "released": 1967,
        "color": true,
        "Actors": [
            "Paul Newman"
        ]
    },
    {
        "Title": "Bullitt",
        "released": 1968,
        "color": true,
        "Actors": [
            "Steve McQueen",
            "Jacqueline Bisset"
        ]
    }
]

解码使用unmarshaling解码成切片，可以选择性解码，即只解出需要的值

var titles []struct{ Title string }
if err := json.Unmarshal(data, &titles); err != nil {
    log.Fatalf("JSON unmarshaling failed: %s", err)
}
fmt.Println(titles) // "[{Casablanca} {Cool Hand Luke} {Bullitt}]"