Go JSON

by Online Tutorials Library July 14, 2022

Go JSON

Go has built-in support for JSON encoding and decoding. it also supports custom datatypes.

The Marshal function is used to convert go data types into JSON format.

Marshal function syntax is:

Marshal returns the JSON encoding of v.

Boolean is converted to JSON booleans. Floating point, integer, and Number are converted to JSON numbers. The map’s key type must either be a string, an integer type, or implement encoding.TextMarshaler.

The decoding of JSON is done using Unmarshal function.

Unmarshal function syntax is:

Unmarshal decodes JSON-encoded value and stores the result in the value pointed to by v. If v is nil or not a pointer, Unmarshal returns an InvalidUnmarshalError.

We can also customize the fields stored under the “json” key in the struct field’s tag. we can have name of the field, followed by a comma-separated list of options. Like

 Field int ‘json:”myName”‘ // The appears in JSON as key “myName”. Field int ‘json:”myName,omitempty?’// The field is omitted from the object if its value is empty, Field int ‘json:”-“‘ //// Field is ignored by this package. 

Go JSON Example 1

 package main import “encoding/json” import “fmt”  func main() { bolType, _ := json.Marshal(false) //boolean Value fmt.Println(string(bolType)) intType, _ := json.Marshal(10) // integer value fmt.Println(string(intType)) fltType, _ := json.Marshal(3.14) //float value fmt.Println(string(fltType)) strType, _ := json.Marshal(“tutoraspire”) // string value fmt.Println(string(strType)) slcA := []string{“sun”, “moon”, “star”} //slice value slcB, _ := json.Marshal(slcA) fmt.Println(string(slcB)) mapA := map[string]int{“sun”: 1, “moon”: 2} //map value mapB, _ := json.Marshal(mapA) fmt.Println(string(mapB)) } 

Output:

false 10 3.14 "tutoraspire" ["sun","moon","star"] {"moon":2,"sun":1}

Go JSON Example 2 (User Defined Data Type)

 package main  import ( “encoding/json” “fmt” “os” )  type Response1 struct { Position   int Planet []string } type Response2 struct { Position   int      ‘json:”position”‘ Planet []string ‘json:”planet”‘ }  func main()  { res1A := &Response1{ Position:   1, Planet: []string{“mercury”, “venus”, “earth”}} res1B, _ := json.Marshal(res1A) fmt.Println(string(res1B))  res2D := &Response2{ Position:   1, Planet: []string{“mercury”, “venus”, “earth”}} res2B, _ := json.Marshal(res2D) fmt.Println(string(res2B))   byt := []byte(‘{“pi”:6.13,”place”:[“New York”,”New Delhi”]}`) var dat map[string]interface{} if err := json.Unmarshal(byt, &dat); err != nil { panic(err) } fmt.Println(dat) num := dat[“pi”].(float64) fmt.Println(num) strs := dat[“place”].([]interface{}) str1 := strs[0].(string) fmt.Println(str1)   str := `{“Position”: 1, “Planet”: [“mercury”, “venus”]}` res := Response2{} json.Unmarshal([]byte(str), &res) fmt.Println(res) fmt.Println(res.Planet[1]) enc := json.NewEncoder(os.Stdout) d := map[string]string{“1″:”mercury” , “2”: “venus”} enc.Encode(d)  } 

Output:

{"Position":1,"Planet":["mercury","venus","earth"]} {"position":1,"planet":["mercury","venus","earth"]} map[pi:6.13 place:[New York New Delhi]] 6.13 New York {1 [mercury venus]} venus {"1":"mercury","2":"venus"}

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Go JSON

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