Working with JSON in Go
Encoding and decoding JSON data in Go applications
🔄 What is JSON in Go?
JSON (JavaScript Object Notation) is a lightweight data format. Go's encoding/json package provides powerful tools to convert Go structs to JSON and vice versa effortlessly.
// Simple JSON marshaling example
package main
import (
"encoding/json"
"fmt"
)
type Person struct {
Name string `json:"name"`
Age int `json:"age"`
}
func main() {
p := Person{Name: "Alice", Age: 30}
jsonData, _ := json.Marshal(p)
fmt.Println(string(jsonData))
}
Output:
{"name":"Alice","age":30}
JSON Operations in Go
Marshal
Convert Go structs to JSON
data, err := json.Marshal(struct)Unmarshal
Convert JSON to Go structs
err := json.Unmarshal(data, &struct)Struct Tags
Control JSON field names
Name string `json:"name"`Custom Types
Handle complex JSON structures
type CustomTime time.Time🔹 JSON Marshal (Encoding)
Convert Go data structures to JSON format:
package main
import (
"encoding/json"
"fmt"
)
type User struct {
ID int `json:"id"`
Name string `json:"name"`
Email string `json:"email"`
Hobbies []string `json:"hobbies"`
Active bool `json:"active"`
}
func main() {
user := User{
ID: 1,
Name: "John Doe",
Email: "[email protected]",
Hobbies: []string{"reading", "coding", "gaming"},
Active: true,
}
// Marshal to JSON
jsonData, err := json.Marshal(user)
if err != nil {
fmt.Println("Error:", err)
return
}
fmt.Println("JSON:", string(jsonData))
// Pretty print JSON
prettyJSON, _ := json.MarshalIndent(user, "", " ")
fmt.Println("Pretty JSON:\n", string(prettyJSON))
}Output:
JSON: {"id":1,"name":"John Doe","email":"[email protected]","hobbies":["reading","coding","gaming"],"active":true}
Pretty JSON:
{
"id": 1,
"name": "John Doe",
"email": "[email protected]",
"hobbies": ["reading","coding","gaming"],
"active": true
}
🔹 JSON Unmarshal (Decoding)
Convert JSON data back to Go structures:
package main
import (
"encoding/json"
"fmt"
)
type Product struct {
ID int `json:"id"`
Name string `json:"name"`
Price float64 `json:"price"`
}
func main() {
// JSON string
jsonStr := `{"id":123,"name":"Laptop","price":999.99}`
// Unmarshal to struct
var product Product
err := json.Unmarshal([]byte(jsonStr), &product)
if err != nil {
fmt.Println("Error:", err)
return
}
fmt.Printf("Product: %+v\n", product)
fmt.Printf("Name: %s, Price: $%.2f\n", product.Name, product.Price)
// Unmarshal to map for dynamic JSON
var data map[string]interface{}
json.Unmarshal([]byte(jsonStr), &data)
fmt.Println("Map:", data)
}Output:
Product: {ID:123 Name:Laptop Price:999.99}
Name: Laptop, Price: $999.99
Map: map[id:123 name:Laptop price:999.99]
🔹 JSON Struct Tags
Control JSON field behavior with struct tags:
package main
import (
"encoding/json"
"fmt"
)
type Employee struct {
ID int `json:"employee_id"`
Name string `json:"full_name"`
Password string `json:"-"` // Ignore field
Email string `json:"email,omitempty"` // Omit if empty
Salary int `json:"salary,string"` // Convert to string
}
func main() {
emp := Employee{
ID: 101,
Name: "Alice Smith",
Password: "secret123",
Email: "",
Salary: 50000,
}
jsonData, _ := json.MarshalIndent(emp, "", " ")
fmt.Println("JSON with tags:")
fmt.Println(string(jsonData))
}Output:
JSON with tags:
{
"employee_id": 101,
"full_name": "Alice Smith",
"salary": "50000"
}
🔹 Working with JSON Files
Read and write JSON data to files:
package main
import (
"encoding/json"
"fmt"
"os"
)
type Config struct {
AppName string `json:"app_name"`
Port int `json:"port"`
Debug bool `json:"debug"`
}
func main() {
// Write JSON to file
config := Config{
AppName: "MyApp",
Port: 8080,
Debug: true,
}
file, _ := os.Create("config.json")
defer file.Close()
encoder := json.NewEncoder(file)
encoder.SetIndent("", " ")
encoder.Encode(config)
fmt.Println("Config saved to file")
// Read JSON from file
var loadedConfig Config
file, _ = os.Open("config.json")
defer file.Close()
decoder := json.NewDecoder(file)
decoder.Decode(&loadedConfig)
fmt.Printf("Loaded config: %+v\n", loadedConfig)
}Output:
Config saved to file
Loaded config: {AppName:MyApp Port:8080 Debug:true}