JSON

This Go code demonstrates the use of the encoding/json package for encoding and decoding JSON data. Let's go through the code with inline comments and explanations:

// Importing necessary packages.
import (
	"encoding/json"
	"fmt"
	"os"
)

// Struct definition for response1.
type response1 struct {
	Page   int
	Fruits []string
}

// Struct definition for response2 with JSON tags.
type response2 struct {
	Page   int      `json:"page"`
	Fruits []string `json:"fruits"`
}

// The main function, where the execution of the program begins.
func main() {
	// Encoding various data types to JSON.

	// Encoding a boolean value.
	bolB, _ := json.Marshal(true)
	fmt.Println(string(bolB))

	// Encoding an integer.
	intB, _ := json.Marshal(1)
	fmt.Println(string(intB))

	// Encoding a float.
	fltB, _ := json.Marshal(2.34)
	fmt.Println(string(fltB))

	// Encoding a string.
	strB, _ := json.Marshal("gopher")
	fmt.Println(string(strB))

	// Encoding a slice of strings.
	slcD := []string{"apple", "peach", "pear"}
	slcB, _ := json.Marshal(slcD)
	fmt.Println(string(slcB))

	// Encoding a map.
	mapD := map[string]int{"apple": 5, "lettuce": 7}
	mapB, _ := json.Marshal(mapD)
	fmt.Println(string(mapB))

	// Encoding a struct (response1).
	res1D := &response1{
		Page:   1,
		Fruits: []string{"apple", "peach", "pear"}}
	res1B, _ := json.Marshal(res1D)
	fmt.Println(string(res1B))

	// Encoding a struct with JSON tags (response2).
	res2D := &response2{
		Page:   1,
		Fruits: []string{"apple", "peach", "pear"}}
	res2B, _ := json.Marshal(res2D)
	fmt.Println(string(res2B))

	// Decoding JSON data.

	// Decoding a JSON byte slice into a map.
	byt := []byte(`{"num":6.13,"strs":["a","b"]}`)
	var dat map[string]interface{}
	if err := json.Unmarshal(byt, &dat); err != nil {
		panic(err)
	}
	fmt.Println(dat)

	// Accessing values from the decoded map.
	num := dat["num"].(float64)
	fmt.Println(num)

	strs := dat["strs"].([]interface{})
	str1 := strs[0].(string)
	fmt.Println(str1)

	// Decoding a JSON string into a struct (response2).
	str := `{"page": 1, "fruits": ["apple", "peach"]}`
	res := response2{}
	json.Unmarshal([]byte(str), &res)
	fmt.Println(res)
	fmt.Println(res.Fruits[0])

	// Encoding a map and writing it to os.Stdout using a JSON encoder.
	enc := json.NewEncoder(os.Stdout)
	d := map[string]int{"apple": 5, "lettuce": 7}
	enc.Encode(d)
}

Output

true
1
2.34
"gopher"
["apple","peach","pear"]
{"apple":5,"lettuce":7}
{"Page":1,"Fruits":["apple","peach","pear"]}
{"page":1,"fruits":["apple","peach","pear"]}
map[num:6.13 strs:[a b]]
6.13
a
{1 [apple peach]}
apple
{"apple":5,"lettuce":7}

Explanation:

1. Encoding:

   • Various types (boolean, integer, float, string, slice, map, and structs) are encoded to JSON using json.Marshal.

2. Structs and JSON Tags:

   • The response1 and response2 structs demonstrate how to use JSON tags for field customization during encoding.

3. Decoding:

   • JSON data is decoded into a map using json.Unmarshal.

   • Values are accessed from the decoded map.

4. Decoding into Structs:

   • JSON data is decoded into a struct (response2 in this case) using json.Unmarshal.

5. JSON Encoder:

   • json.NewEncoder is used to create a JSON encoder that writes to os.Stdout.

   • A map is encoded and written to os.Stdout using the encoder.

This code illustrates the basic usage of the encoding/json package in Go for encoding and decoding JSON data.