viper 学习笔记

viper

Functional options

在 c# 等语言中，一般多个参数这么实现

funcion add(){

}
funcion add(int a){

}
funcion add(int a,int b){

}

在 golang 中，由于没有重载，在实现多个参数是会比较麻烦，可能的实现方式是

func add(){

}
func adda(a int){

}
func addab(a int,b int){

}

这种方式的扩展性较差，因此提倡一种使用 functional option，使用函数参数的方式来进行参数赋值

type optionFunc func(options *option)

func seta(int a) optionFunc{
    return optionFunc(func(options *option){
        options.a = a;
    })
}

func add(opts ...optionFunc){
	for _, opt := range opts {
		opt(v)
	}
}

当然，还可以利用接口来承载函数，

type Option interface {
	apply(v *Viper)
}

type optionFunc func(v *Viper)

func (fn optionFunc) apply(v *Viper) {
	fn(v)
}
func KeyDelimiter(d string) Option {
	return optionFunc(func(v *Viper) {
		v.keyDelim = d
	})
}

func NewWithOptions(opts ...Option) *Viper {
	v := New()

	for _, opt := range opts {
		opt.apply(v)
	}

	return v
}

基本用法

viper.SetConfigName("config") // name of config file (without extension)
viper.SetConfigType("yaml") // REQUIRED if the config file does not have the extension in the name
viper.AddConfigPath("/etc/appname/")   // path to look for the config file in
viper.AddConfigPath("$HOME/.appname")  // call multiple times to add many search paths
viper.AddConfigPath(".")               // optionally look for config in the working directory
err := viper.ReadInConfig() // Find and read the config file
if err != nil { // Handle errors reading the config file
	panic(fmt.Errorf("Fatal error config file: %s \n", err))
}

核心方法:

func (v *Viper) ReadInConfig() error {
	jww.INFO.Println("Attempting to read in config file")
	filename, err := v.getConfigFile()
	if err != nil {
		return err
	}

	if !stringInSlice(v.getConfigType(), SupportedExts) {
		return UnsupportedConfigError(v.getConfigType())
	}

	jww.DEBUG.Println("Reading file: ", filename)
	file, err := afero.ReadFile(v.fs, filename)
	if err != nil {
		return err
	}

	config := make(map[string]interface{})

	err = v.unmarshalReader(bytes.NewReader(file), config)
	if err != nil {
		return err
	}

	v.config = config
	return nil
}


func (v *Viper) unmarshalReader(in io.Reader, c map[string]interface{}) error {
	buf := new(bytes.Buffer)
	buf.ReadFrom(in)

	switch strings.ToLower(v.getConfigType()) {
	case "yaml", "yml":
		if err := yaml.Unmarshal(buf.Bytes(), &c); err != nil {
			return ConfigParseError{err}
		}

	case "json":
		if err := json.Unmarshal(buf.Bytes(), &c); err != nil {
			return ConfigParseError{err}
		}

	case "hcl":
		obj, err := hcl.Parse(buf.String())
		if err != nil {
			return ConfigParseError{err}
		}
		if err = hcl.DecodeObject(&c, obj); err != nil {
			return ConfigParseError{err}
		}

	case "toml":
		tree, err := toml.LoadReader(buf)
		if err != nil {
			return ConfigParseError{err}
		}
		tmap := tree.ToMap()
		for k, v := range tmap {
			c[k] = v
		}

	case "dotenv", "env":
		env, err := gotenv.StrictParse(buf)
		if err != nil {
			return ConfigParseError{err}
		}
		for k, v := range env {
			c[k] = v
		}

	case "properties", "props", "prop":
		v.properties = properties.NewProperties()
		var err error
		if v.properties, err = properties.Load(buf.Bytes(), properties.UTF8); err != nil {
			return ConfigParseError{err}
		}
		for _, key := range v.properties.Keys() {
			value, _ := v.properties.Get(key)
			// recursively build nested maps
			path := strings.Split(key, ".")
			lastKey := strings.ToLower(path[len(path)-1])
			deepestMap := deepSearch(c, path[0:len(path)-1])
			// set innermost value
			deepestMap[lastKey] = value
		}

	case "ini":
		cfg := ini.Empty()
		err := cfg.Append(buf.Bytes())
		if err != nil {
			return ConfigParseError{err}
		}
		sections := cfg.Sections()
		for i := 0; i < len(sections); i++ {
			section := sections[i]
			keys := section.Keys()
			for j := 0; j < len(keys); j++ {
				key := keys[j]
				value := cfg.Section(section.Name()).Key(key.Name()).String()
				c[section.Name()+"."+key.Name()] = value
			}
		}
	}

	insensitiviseMap(c)
	return nil
}

查找核心代码

// Given a key, find the value.
//
// Viper will check to see if an alias exists first.
// Viper will then check in the following order:
// flag, env, config file, key/value store.
// Lastly, if no value was found and flagDefault is true, and if the key
// corresponds to a flag, the flag's default value is returned.
//
// Note: this assumes a lower-cased key given.
func (v *Viper) find(lcaseKey string, flagDefault bool) interface{} {
	var (
		val    interface{}
		exists bool
		path   = strings.Split(lcaseKey, v.keyDelim)
		nested = len(path) > 1
	)

	// compute the path through the nested maps to the nested value
	if nested && v.isPathShadowedInDeepMap(path, castMapStringToMapInterface(v.aliases)) != "" {
		return nil
	}

	// if the requested key is an alias, then return the proper key
	lcaseKey = v.realKey(lcaseKey)
	path = strings.Split(lcaseKey, v.keyDelim)
	nested = len(path) > 1

	// Set() override first
	val = v.searchMap(v.override, path)
	if val != nil {
		return val
	}
	if nested && v.isPathShadowedInDeepMap(path, v.override) != "" {
		return nil
	}

	// PFlag override next
	flag, exists := v.pflags[lcaseKey]
	if exists && flag.HasChanged() {
		switch flag.ValueType() {
		case "int", "int8", "int16", "int32", "int64":
			return cast.ToInt(flag.ValueString())
		case "bool":
			return cast.ToBool(flag.ValueString())
		case "stringSlice":
			s := strings.TrimPrefix(flag.ValueString(), "[")
			s = strings.TrimSuffix(s, "]")
			res, _ := readAsCSV(s)
			return res
		case "intSlice":
			s := strings.TrimPrefix(flag.ValueString(), "[")
			s = strings.TrimSuffix(s, "]")
			res, _ := readAsCSV(s)
			return cast.ToIntSlice(res)
		case "stringToString":
			return stringToStringConv(flag.ValueString())
		default:
			return flag.ValueString()
		}
	}
	if nested && v.isPathShadowedInFlatMap(path, v.pflags) != "" {
		return nil
	}

	// Env override next
	if v.automaticEnvApplied {
		// even if it hasn't been registered, if automaticEnv is used,
		// check any Get request
		if val, ok := v.getEnv(v.mergeWithEnvPrefix(lcaseKey)); ok {
			return val
		}
		if nested && v.isPathShadowedInAutoEnv(path) != "" {
			return nil
		}
	}
	envkeys, exists := v.env[lcaseKey]
	if exists {
		for _, envkey := range envkeys {
			if val, ok := v.getEnv(envkey); ok {
				return val
			}
		}
	}
	if nested && v.isPathShadowedInFlatMap(path, v.env) != "" {
		return nil
	}

	// Config file next
	val = v.searchIndexableWithPathPrefixes(v.config, path)
	if val != nil {
		return val
	}
	if nested && v.isPathShadowedInDeepMap(path, v.config) != "" {
		return nil
	}

	// K/V store next
	val = v.searchMap(v.kvstore, path)
	if val != nil {
		return val
	}
	if nested && v.isPathShadowedInDeepMap(path, v.kvstore) != "" {
		return nil
	}

	// Default next
	val = v.searchMap(v.defaults, path)
	if val != nil {
		return val
	}
	if nested && v.isPathShadowedInDeepMap(path, v.defaults) != "" {
		return nil
	}

	if flagDefault {
		// last chance: if no value is found and a flag does exist for the key,
		// get the flag's default value even if the flag's value has not been set.
		if flag, exists := v.pflags[lcaseKey]; exists {
			switch flag.ValueType() {
			case "int", "int8", "int16", "int32", "int64":
				return cast.ToInt(flag.ValueString())
			case "bool":
				return cast.ToBool(flag.ValueString())
			case "stringSlice":
				s := strings.TrimPrefix(flag.ValueString(), "[")
				s = strings.TrimSuffix(s, "]")
				res, _ := readAsCSV(s)
				return res
			case "intSlice":
				s := strings.TrimPrefix(flag.ValueString(), "[")
				s = strings.TrimSuffix(s, "]")
				res, _ := readAsCSV(s)
				return cast.ToIntSlice(res)
			case "stringToString":
				return stringToStringConv(flag.ValueString())
			default:
				return flag.ValueString()
			}
		}
		// last item, no need to check shadowing
	}

	return nil
}