Golang反射实现动态配置加载实践

type DatabaseConfig struct {
  Host string `config:"host"`
  Port int    `config:"port"`
  SSL  bool   `config:"ssl_enabled"`
}

type AppConfig struct {
  Name      string          `config:"app_name"`
  Debug     bool            `config:"debug"`
  Database  DatabaseConfig  `config:"database"`
  Hosts     []string        `config:"allowed_hosts"`
}

func LoadConfig(config interface{}, data map[string]interface{}) error {
  v := reflect.ValueOf(config)
  if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
    return fmt.Errorf("config must be a pointer to struct")
  }
  return setValue(v.Elem(), data)
}

func setValue(v reflect.Value, data map[string]interface{}) error {
  t := v.Type()
  for i := 0; i < v.NumField(); i++ {
    field := v.Field(i)
    structField := t.Field(i)

    if !field.CanSet() {
      continue
    }

    key := structField.Tag.Get("config")
    if key == "" {
      key = strings.ToLower(structField.Name)
    }

    value, exists := data[key]
    if !exists {
      continue
    }

    switch field.Kind() {
    case reflect.String:
      field.SetString(value.(string))
    case reflect.Int, reflect.Int32, reflect.Int64:
      field.SetInt(int64(value.(float64))) // JSON数字默认为float64
    case reflect.Bool:
      field.SetBool(value.(bool))
    case reflect.Slice:
      if reflect.TypeOf(value).Kind() == reflect.Slice {
        sliceVal := reflect.ValueOf(value)
        newSlice := reflect.MakeSlice(field.Type(), sliceVal.Len(), sliceVal.Len())
        reflect.Copy(newSlice, sliceVal)
        field.Set(newSlice)
      }
    case reflect.Struct:
      subData, ok := value.(map[string]interface{})
      if ok {
        setValue(field, subData)
      }
    }
  }
  return nil
}

rawConfig := map[string]interface{}{
  "app_name": "my-service",
  "debug": true,
  "database": map[string]interface{}{
    "host": "localhost",
    "port": 5432,
    "ssl_enabled": false,
  },
  "allowed_hosts": []interface{}{"127.0.0.1", "localhost"},
}

var cfg AppConfig
err := LoadConfig(&cfg, rawConfig)
if err != nil {
  log.Fatal(err)
}
fmt.Printf("%+v\n", cfg)