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This article focuses on "how to use the Goto language JSON standard library", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to use the JSON standard library of GE language.

Serialization

Serialization uses the Marshal function in the json library:

Func Marshal (v interface {}) ([] byte, error) 1. Structural body serialization

For example, use the following structure to represent a movie:

Type Movie struct {Title string Year int `json: "released" `Color bool `json: "color,omitempty" `Actors [] string}

The type in the definition is followed by the string json: "released" and json: "color,omitempty, called field tags, which tells the json library some rules when performing serialization:

Json: "released" so that the corresponding name after serialization is "released" instead of "Year".

Json: "color,omitempty" so that if the value of the Color member is false, then ignore it and not serialize it.

Some rules for serialization without field tags:

If the name of a structure member does not begin with an uppercase letter, it is not serialized.

If the name of a structure member begins with an uppercase letter, the serialized name is the member name.

The code for serialization is as follows:

Movie: = Movie {Title: "Casablanca", Year: 1942, Color: false, Actors: [] string {"Humphrey Bogart", "Ingrid Bergman"},} data, err: = json.Marshal (movie) if err! = nil {log.Fatalf ("JSON marshaling failed:% s" Err)} fmt.Printf ("% s\ n", data)

Output:

{"Title": "Casablanca", "released": 1942, "Actors": ["Humphrey Bogart", "Ingrid Bergman"]}

two。 Dictionary serialization

For a dictionary to be serialized into-JSON format, its key must be a string.

Here is an example:

Info: = map [string] int {"width": 1280, "height": 720,} data, err: = json.MarshalIndent (info, "", ") if err! = nil {log.Fatalf (" JSON marshaling failed:% s ", err)} fmt.Printf ("% s\ n ", data)

Output:

{

Height: 720

"width": 1280

}

Here we use the MarshalIndent function to make the output JSON format easier to read. The serialized name is the name of key in the dictionary.

3. Slice serialization

Look directly at an example:

Type Movie struct {Title string Year int `json: "released" `Color bool `json: "color,omitempty" `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"} },} data, err: = json.MarshalIndent (movies, ",") if err! = nil {log.Fatalf ("JSON marshaling failed:% s", err)} fmt.Printf ("% s\ n", data)

Output:

[

{

"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"

]

}

]

Deserialization

Deserialization uses the Unmarshal function:

Func Unmarshal (data [] byte, v interface {}) error1. Clear knowledge of JSON format

We need to first represent the JSON format as a definite type.

1. The following JSON format:

{"name": "Awesome 4K", "resolutions": [{"width": 1280, "height": 720} {"width": 1920, "height": 1080}, {"width": 3840 "height": 2160}]}

We can represent it with the following structure:

Struct {Name string Resolutions [] struct {Width int Height int}}

two。 The following JSON format:

{"height": 720, "width": 1280}

You can also use map [string] int, that is, a dictionary.

3. The following JSON format:

[{"width": 1280, "height": 720}, {"width": 1920, "height": 1080}, {"width": 3840, "height": 2160}]

Represented by a slice [] map [string] int.

In any case, a definite JSON format can always be represented using slices, structures, or dictionaries.

You can then deserialize:

Var jsonBlob = [] byte (`[{"width": 1280, "height": 720}, {"width": 1920) "height": 1080,}, {"width": 3840 "height": 2160}] `) di: = [] map [string] int {} err = json.Unmarshal (jsonBlob, & di) if err! = nil {fmt.Println ("error:", err)} fmt.Printf ("% + v\ n", di)

Output

[map [height:720 width:1280] map [height:1080 width:1920] map [height:2160 width:3840]]

two。 Unable to determine JSON format

Formats that cannot be determined can be represented directly using the interface {} type. At this point, if it is a JSON object, the json library will use the mapping [string] interface {} type to represent it when deserializing. If it is a JSON array, it is represented by the [] interface {} type. For a specific type corresponding to interface {}, you need to use type assertions.

Take a specific look at an example:

Package mainimport ("encoding/json"fmt") func main () {var jsonBlob = [] byte (`{"name": "Awesome 4K", "price": 1999.9 "resolutions": [{"width": 1280, "height": 720} {"width": 1920, "height": 1080}, {"width": 3840 "height": 2160}]} `) var d interface {} err: = json.Unmarshal (jsonBlob, & d) if err! = nil {fmt.Println ("error:" Err)} fmt.Println (d) m: = d. (map [string] interface {}) for k, v: = range m {switch vv: = v. (type) {case string: fmt.Println (k, "is string") Vv) case float64: fmt.Println (k, "is float64", vv) case [] interface {}: fmt.Println (k, "is an array:") for I, u: = range vv {fmt.Println (I) U)} default: fmt.Println (k, "is of a type I don't know how to handle")}

Output:

Map [name:Awesome 4K price:1999.9 resolutions: [map[height: 720 width:1280] map [height:1080 width:1920] map [height:2160 width:3840]

Resolutions is an array:

0 map [height:720 width:1280]

1 map [height:1080 width:1920]

2 map [height:2160 width:3840]

Name is string Awesome 4K

Price is float64 1999.9

At this point, I believe you have a deeper understanding of "how to use the GE language JSON standard library". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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