decoder

README

data-decoder

A data decoding util based on mapstructure package The main target of this package is to solve the problem when requiring nested values from viper. Viper doesn't process environment values as structured value, this causes problem when unmarshalling value to structs. Decoder requires value for nested struct fields particularly if it's not found from the data map required for it's parent struct. Environment values are used if the value is not defined in map-typed data in config files.

Examples

Environments

LOGGING_FILE_PATH=decoder.log

viper vs data-decoder

Contents in yaml file

logging:
  level: debug

Logging Config Model

type LoggingConfigModel1 struct {
	Level string
	File  struct {
		Path string
	}
}

Using viper

Code

v := viper.New()
cfgFilePath := filepath.Join(os.Getenv("PROJECT_PATH"), "test", "decode_logging_config", "config.yaml")
v.SetConfigFile(cfgFilePath)
v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
v.AutomaticEnv()

v.MergeInConfig()
cfgModel := LoggingConfigModel1{}
fmt.Println("logging.file.path:", v.Get("logging.file.path"))
v.UnmarshalKey("logging", &cfgModel)
fmt.Println("cfgModel:", cfgModel)

Result

logging.file.path: decoder.log
cfgModel: {debug {}}

Using data-decoder

Code

v := viper.New()
cfgFilePath := filepath.Join(os.Getenv("PROJECT_PATH"), "test", "decode_logging_config", "config.yaml")
v.SetConfigFile(cfgFilePath)
v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
v.AutomaticEnv()
v.MergeInConfig()

d := decoder.NewDecoder(v)

cfgModel := LoggingConfigModel1{}
fmt.Println("logging.file.path:", v.Get("logging.file.path"))
d.Decode("logging", &cfgModel)
fmt.Println("cfgModel:", cfgModel)

Result

logging.file.path: decoder.log
cfgModel: {debug {decoder.log}}

Using query options

Disable nested query

Models

type LoggingConfigModel2 struct {
	Level string
	File  struct {
		Path string `query-option:"no"`
	}
}

type LoggingConfigModel3 struct {
	Level string
	File  struct {
		Path string
	} `query-option:"no"`
}

Code

v := viper.New()
cfgFilePath := filepath.Join(os.Getenv("PROJECT_PATH"), "test", "decode_logging_config", "config.yaml")
v.SetConfigFile(cfgFilePath)
v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
v.AutomaticEnv()
v.MergeInConfig()

d := decoder.NewDecoder(v)

cfgModel2 := LoggingConfigModel2{}
fmt.Println(v.Get("logging.file.path"))
d.Decode("logging", &cfgModel2)
fmt.Println("cfgModel2:", cfgModel2)

cfgModel3 := LoggingConfigModel3{}
fmt.Println(v.Get("logging.file.path"))
d.Decode("logging", &cfgModel3)
fmt.Println("cfgModel3:", cfgModel3)

Result

decoder.log
cfgModel2: {debug {}}
decoder.log
cfgModel3: {debug {}}

Use bypass together with viper alias

Environment

LOGGING_CONFIG_FILE=decoder.log

Model

type LoggingConfigModel4 struct {
	Level string
	File  struct {
		Path string
	} `query-option:"bypass"`
}

Code

v := viper.New()
cfgFilePath := filepath.Join(os.Getenv("PROJECT_PATH"), "test", "decode_logging_config", "config.yaml")
v.SetConfigFile(cfgFilePath)
v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
v.AutomaticEnv()
v.MergeInConfig()

v.RegisterAlias("logging.file.path", "logging.file")

d := decoder.NewDecoder(v)
cfgModel4 := LoggingConfigModel4{}
fmt.Println(v.Get("logging.file.path"))
d.Decode("logging", &cfgModel4)
fmt.Println("cfgModel4:", cfgModel4)

Result

decoder.log
cfgModel4: {debug {decoder.log}}

Documentation

Index

• Constants
• func ComposeDecodeHookFunc(fs ...DecodeHookFunc) mapstructure.DecodeHookFunc
• func DecodeStructuredString(ctx *DecodeContext, targetType reflect.Type) error
• func UnmarshalMapToStruct(ctx *DecodeContext, targetType reflect.Type) error
• type DataProvider
• type DecodeContext
  • func (ctx *DecodeContext) Done()
• type DecodeHookFunc
• type Decoder
  • func NewDecoder(dp DataProvider) *Decoder
  • func (d *Decoder) Decode(key string, output interface{}) error
• type QueryOptionType

Constants

const (
	QO_ALWAYS QueryOptionType = "always" // always query data from data provider
	QO_AUTO                   = ""       // query data if data is nil
	QO_NO                     = "no"     // never query data from data provider for current field node and its children
	QO_BYPASS                 = "bypass" // never query data for the current field node
)

Functions

func ComposeDecodeHookFunc

func ComposeDecodeHookFunc(fs ...DecodeHookFunc) mapstructure.DecodeHookFunc

func DecodeStructuredString

func DecodeStructuredString(ctx *DecodeContext, targetType reflect.Type) error

func UnmarshalMapToStruct

func UnmarshalMapToStruct(ctx *DecodeContext, targetType reflect.Type) error

Types

type DataProvider

type DataProvider interface {
	Get(key string) interface{}
}

type DecodeContext

type DecodeContext struct {
	Data        interface{}
	QueryKey    string
	QueryOption QueryOptionType
	// contains filtered or unexported fields
}

func (*DecodeContext) Done

func (ctx *DecodeContext) Done()

type DecodeHookFunc

type DecodeHookFunc func(*DecodeContext, reflect.Type) error

type Decoder

type Decoder struct {
	// contains filtered or unexported fields
}

func NewDecoder

func NewDecoder(dp DataProvider) *Decoder

func (*Decoder) Decode

func (d *Decoder) Decode(key string, output interface{}) error

type QueryOptionType

type QueryOptionType string