991 lines
32 KiB
Go
991 lines
32 KiB
Go
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// The mapstructure package exposes functionality to convert an
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// abitrary map[string]interface{} into a native Go structure.
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//
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// The Go structure can be arbitrarily complex, containing slices,
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// other structs, etc. and the decoder will properly decode nested
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// maps and so on into the proper structures in the native Go struct.
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// See the examples to see what the decoder is capable of.
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package mapstructure
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import (
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"errors"
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"fmt"
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"reflect"
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"sort"
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"strconv"
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"strings"
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)
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//read note 钩子，起作用的地方是在Decode之前，这边主要的作用可以说比如 在转换之前把字符串转成Time类型等等，具体可以查看：https://godoc.org/github.com/mitchellh/mapstructure#DecodeHookFunc
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//read note https://github.com/mitchellh/mapstructure/blob/master/decode_hooks.go 这边提供了一些默认的hook方法，可以看一下
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type DecodeHookFunc func(reflect.Kind, reflect.Kind, interface{}) (interface{}, error)
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// DecoderConfig is the configuration that is used to create a new decoder
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// and allows customization of various aspects of decoding.
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type DecoderConfig struct {
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// DecodeHook, if set, will be called before any decoding and any
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// type conversion (if WeaklyTypedInput is on). This lets you modify
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// the values before they're set down onto the resulting struct.
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//
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// If an error is returned, the entire decode will fail with that
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// error.
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//read note 在Decode之前会调用该Hook,这边的注释说明,hook可以让你在Decode之前修改你的结构体现有值
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DecodeHook DecodeHookFunc
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// If ErrorUnused is true, then it is an error for there to exist
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// keys in the original map that were unused in the decoding process
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// (extra keys).
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//read note 如果这个字段设置为true的话，在map当中只要有key不能转换成结构体的字段就会进行报错，感觉正常情况下是不会设置成true...
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ErrorUnused bool
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// If WeaklyTypedInput is true, the decoder will make the following
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// "weak" conversions:
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//
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// - bools to string (true = "1", false = "0")
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// - numbers to string (base 10)
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// - bools to int/uint (true = 1, false = 0)
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// - strings to int/uint (base implied by prefix)
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// - int to bool (true if value != 0)
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// - string to bool (accepts: 1, t, T, TRUE, true, True, 0, f, F,
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// FALSE, false, False. Anything else is an error)
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// - empty array = empty map and vice versa
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//
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//read note 弱类型转换，这个字段如果设置为true，则从某种类型 to 某种类型 会按照上面的转换规则来进行转换
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WeaklyTypedInput bool
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// Metadata is the struct that will contain extra metadata about
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// the decoding. If this is nil, then no metadata will be tracked.
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//read note 没搞明白这个是干啥的
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Metadata *Metadata
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// Result is a pointer to the struct that will contain the decoded
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// value.
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//read note 转换的结果
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Result interface{}
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// The tag name that mapstructure reads for field names. This
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// defaults to "mapstructure"
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//read note tag名称，默认是 mapstructure
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TagName string
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}
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// A Decoder takes a raw interface value and turns it into structured
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// data, keeping track of rich error information along the way in case
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// anything goes wrong. Unlike the basic top-level Decode method, you can
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// more finely control how the Decoder behaves using the DecoderConfig
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// structure. The top-level Decode method is just a convenience that sets
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// up the most basic Decoder.
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type Decoder struct {
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//read note 转换工具的配置
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config *DecoderConfig
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}
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// Metadata contains information about decoding a structure that
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// is tedious or difficult to get otherwise.
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type Metadata struct {
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// Keys are the keys of the structure which were successfully decoded
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Keys []string
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// Unused is a slice of keys that were found in the raw value but
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// weren't decoded since there was no matching field in the result interface
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Unused []string
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}
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// Decode takes a map and uses reflection to convert it into the
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// given Go native structure. val must be a pointer to a struct.
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func Decode(m interface{}, rawVal interface{}) error {
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config := &DecoderConfig{
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Metadata: nil,
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Result: rawVal,
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}
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//read note 创建包含配置的Decoder对象
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decoder, err := NewDecoder(config)
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if err != nil {
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return err
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}
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//read note 进行Decode操作
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return decoder.Decode(m)
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}
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// DecodePath takes a map and uses reflection to convert it into the
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// given Go native structure. Tags are used to specify the mapping
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// between fields in the map and structure
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func DecodePath(m map[string]interface{}, rawVal interface{}) error {
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config := &DecoderConfig{
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Metadata: nil,
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Result: nil,
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}
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decoder, err := NewPathDecoder(config)
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if err != nil {
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return err
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}
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_, err = decoder.DecodePath(m, rawVal)
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return err
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}
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// DecodeSlicePath decodes a slice of maps against a slice of structures that
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// contain specified tags
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func DecodeSlicePath(ms []map[string]interface{}, rawSlice interface{}) error {
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reflectRawSlice := reflect.TypeOf(rawSlice)
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rawKind := reflectRawSlice.Kind()
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rawElement := reflectRawSlice.Elem()
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//read note 校验是否为切片
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if (rawKind == reflect.Ptr && rawElement.Kind() != reflect.Slice) ||
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(rawKind != reflect.Ptr && rawKind != reflect.Slice) {
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return fmt.Errorf("Incompatible Value, Looking For Slice : %v : %v", rawKind, rawElement.Kind())
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}
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config := &DecoderConfig{
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Metadata: nil,
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Result: nil,
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}
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decoder, err := NewPathDecoder(config)
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if err != nil {
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return err
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}
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// Create a slice large enough to decode all the values
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//read note 构造一个新的数组
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valSlice := reflect.MakeSlice(rawElement, len(ms), len(ms))
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// Iterate over the maps and decode each one
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//read note 循环被转换的map数组
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for index, m := range ms {
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sliceElementType := rawElement.Elem()
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if sliceElementType.Kind() != reflect.Ptr {
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// A slice of objects
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//read note 如果转换的结果是结构体类型，处理转换
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obj := reflect.New(rawElement.Elem())
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decoder.DecodePath(m, reflect.Indirect(obj))
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indexVal := valSlice.Index(index)
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indexVal.Set(reflect.Indirect(obj))
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} else {
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// A slice of pointers
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//read note 如果转换的结果是指针类型，处理转换
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obj := reflect.New(rawElement.Elem().Elem())
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decoder.DecodePath(m, reflect.Indirect(obj))
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indexVal := valSlice.Index(index)
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indexVal.Set(obj)
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}
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}
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// Set the new slice
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//read note 设置转换后的数组数据
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reflect.ValueOf(rawSlice).Elem().Set(valSlice)
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return nil
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}
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// NewDecoder returns a new decoder for the given configuration. Once
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// a decoder has been returned, the same configuration must not be used
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// again.
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func NewDecoder(config *DecoderConfig) (*Decoder, error) {
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val := reflect.ValueOf(config.Result)
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if val.Kind() != reflect.Ptr {
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return nil, errors.New("result must be a pointer")
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}
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val = val.Elem()
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if !val.CanAddr() {
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return nil, errors.New("result must be addressable (a pointer)")
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}
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if config.Metadata != nil {
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if config.Metadata.Keys == nil {
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config.Metadata.Keys = make([]string, 0)
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}
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if config.Metadata.Unused == nil {
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config.Metadata.Unused = make([]string, 0)
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}
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}
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if config.TagName == "" {
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config.TagName = "mapstructure"
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}
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result := &Decoder{
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config: config,
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}
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return result, nil
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}
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// NewPathDecoder returns a new decoder for the given configuration.
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// This is used to decode path specific structures
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func NewPathDecoder(config *DecoderConfig) (*Decoder, error) {
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if config.Metadata != nil {
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if config.Metadata.Keys == nil {
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config.Metadata.Keys = make([]string, 0)
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}
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if config.Metadata.Unused == nil {
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config.Metadata.Unused = make([]string, 0)
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}
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}
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if config.TagName == "" {
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config.TagName = "mapstructure"
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}
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result := &Decoder{
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config: config,
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}
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return result, nil
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}
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// Decode decodes the given raw interface to the target pointer specified
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// by the configuration.
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func (d *Decoder) Decode(raw interface{}) error {
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//read note config中的Result配置的是指针，如果不是指针是没办法完成配置的.
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// 所有这边的调用是通过 reflect.ValueOf().Elem()
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return d.decode("", raw, reflect.ValueOf(d.config.Result).Elem())
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}
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// DecodePath decodes the raw interface against the map based on the
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// specified tags
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func (d *Decoder) DecodePath(m map[string]interface{}, rawVal interface{}) (bool, error) {
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decoded := false
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var val reflect.Value
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reflectRawValue := reflect.ValueOf(rawVal)
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kind := reflectRawValue.Kind()
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// Looking for structs and pointers to structs
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//read note 对传入的 转换结果的数据类型进行判断，转换成对应的结构体类型
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switch kind {
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case reflect.Ptr:
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val = reflectRawValue.Elem()
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if val.Kind() != reflect.Struct {
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return decoded, fmt.Errorf("Incompatible Type : %v : Looking For Struct", kind)
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}
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case reflect.Struct:
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var ok bool
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val, ok = rawVal.(reflect.Value)
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if ok == false {
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return decoded, fmt.Errorf("Incompatible Type : %v : Looking For reflect.Value", kind)
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}
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default:
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return decoded, fmt.Errorf("Incompatible Type : %v", kind)
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}
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// Iterate over the fields in the struct
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//read note 循环结构体的所有Field
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for i := 0; i < val.NumField(); i++ {
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valueField := val.Field(i)
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typeField := val.Type().Field(i)
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tag := typeField.Tag
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//read note 这边的tag是通过 jpath来识别的
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tagValue := tag.Get("jpath")
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// Is this a field without a tag
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//read note 没有tag的单独处理
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if tagValue == "" {
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//read note 如果是结构体，调用DecodePath处理
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if valueField.Kind() == reflect.Struct {
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// We have a struct that may have indivdual tags. Process separately
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d.DecodePath(m, valueField)
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continue
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} else if valueField.Kind() == reflect.Ptr && reflect.TypeOf(valueField).Kind() == reflect.Struct {
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//read note 指针的处理，转换成结构体也是类型的DecodePath的处理
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// We have a pointer to a struct
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if valueField.IsNil() {
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// Create the object since it doesn't exist
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valueField.Set(reflect.New(valueField.Type().Elem()))
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decoded, _ = d.DecodePath(m, valueField.Elem())
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if decoded == false {
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// If nothing was decoded for this object return the pointer to nil
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valueField.Set(reflect.NewAt(valueField.Type().Elem(), nil))
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}
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continue
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}
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d.DecodePath(m, valueField.Elem())
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continue
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}
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}
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// Use mapstructure to populate the fields
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//read note jpath后面支持的别名可以是递进到更进去的层次，通过.标识，比如说 Age.Birth. 表示 Age:{Birth:100,。。。}
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keys := strings.Split(tagValue, ".")
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//read note 通过keys去查找数据
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data := d.findData(m, keys)
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//read note 如果在map中找到的数据不为nil。需要开始设值操作
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if data != nil {
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//read note 如果当前Filed的类型是Slice
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if valueField.Kind() == reflect.Slice {
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// Ignore a slice of maps - This sucks but not sure how to check
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//read note 如果Field是map数组，这边没办法处理，只能通过下面的decode方法进行具体的处理
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if strings.Contains(valueField.Type().String(), "map[") {
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goto normal_decode
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}
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// We have a slice
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mapSlice := data.([]interface{})
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if len(mapSlice) > 0 {
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// Test if this is a slice of more maps
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//read note 转换成切片的数据如果不是 map的数组，则跳转到下面通过 decode处理.因为这边是切片对切片，map对结构体
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_, ok := mapSlice[0].(map[string]interface{})
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if ok == false {
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goto normal_decode
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}
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// Extract the maps out and run it through DecodeSlicePath
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//read note 组转map数组
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|
ms := make([]map[string]interface{}, len(mapSlice))
|
|||
|
|
for index, m2 := range mapSlice {
|
|||
|
|
ms[index] = m2.(map[string]interface{})
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//调用DecodeSlicePath，转换 map数组 -》 结构体数组
|
|||
|
|
DecodeSlicePath(ms, valueField.Addr().Interface())
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
normal_decode:
|
|||
|
|
//read note 通过decode处理，这边同样应该支持 mapstructure的tag标签
|
|||
|
|
decoded = true
|
|||
|
|
err := d.decode("", data, valueField)
|
|||
|
|
if err != nil {
|
|||
|
|
return false, err
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return decoded, nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Decodes an unknown data type into a specific reflection value.
|
|||
|
|
//read note 入参说明：
|
|||
|
|
// name： 字段名称
|
|||
|
|
// data： 被转换的数据
|
|||
|
|
// val ： 转换最终的结构体
|
|||
|
|
func (d *Decoder) decode(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
//read note 结构体为空直接返回
|
|||
|
|
if data == nil {
|
|||
|
|
// If the data is nil, then we don't set anything.
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
dataVal := reflect.ValueOf(data)
|
|||
|
|
//read note 非IsValid的对象，设置零值
|
|||
|
|
if !dataVal.IsValid() {
|
|||
|
|
// If the data value is invalid, then we just set the value
|
|||
|
|
// to be the zero value.
|
|||
|
|
val.Set(reflect.Zero(val.Type()))
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note hook的调用，调用的结果data会用在下面的判断中
|
|||
|
|
if d.config.DecodeHook != nil {
|
|||
|
|
// We have a DecodeHook, so let's pre-process the data.
|
|||
|
|
var err error
|
|||
|
|
data, err = d.config.DecodeHook(d.getKind(dataVal), d.getKind(val), data)
|
|||
|
|
if err != nil {
|
|||
|
|
return err
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
var err error
|
|||
|
|
//read note 获得 转换最终的结构体 的类型
|
|||
|
|
dataKind := d.getKind(val)
|
|||
|
|
//read note 依据类型进行不同的转换处理
|
|||
|
|
switch dataKind {
|
|||
|
|
case reflect.Bool:
|
|||
|
|
err = d.decodeBool(name, data, val)
|
|||
|
|
case reflect.Interface:
|
|||
|
|
err = d.decodeBasic(name, data, val)
|
|||
|
|
case reflect.String:
|
|||
|
|
err = d.decodeString(name, data, val)
|
|||
|
|
case reflect.Int:
|
|||
|
|
err = d.decodeInt(name, data, val)
|
|||
|
|
case reflect.Uint:
|
|||
|
|
err = d.decodeUint(name, data, val) //read note 处理与decodeInt类似
|
|||
|
|
case reflect.Float32:
|
|||
|
|
err = d.decodeFloat(name, data, val) //read note 处理与decodeInt类似
|
|||
|
|
case reflect.Struct:
|
|||
|
|
err = d.decodeStruct(name, data, val)
|
|||
|
|
case reflect.Map:
|
|||
|
|
err = d.decodeMap(name, data, val)
|
|||
|
|
case reflect.Slice:
|
|||
|
|
err = d.decodeSlice(name, data, val)
|
|||
|
|
default:
|
|||
|
|
// If we reached this point then we weren't able to decode it
|
|||
|
|
//read note 没办法处理指针类型,比如本来传入的就是指针的指针，这边是拒绝处理的
|
|||
|
|
return fmt.Errorf("%s: unsupported type: %s", name, dataKind)
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// If we reached here, then we successfully decoded SOMETHING, so
|
|||
|
|
// mark the key as used if we're tracking metadata.
|
|||
|
|
//read note 对处理玩的Metadata进行组装，但是这边看好像一定是不会处理的，因为传进来的name一直是空字符串
|
|||
|
|
if d.config.Metadata != nil && name != "" {
|
|||
|
|
d.config.Metadata.Keys = append(d.config.Metadata.Keys, name)
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return err
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// findData locates the data by walking the keys down the map
|
|||
|
|
func (d *Decoder) findData(m map[string]interface{}, keys []string) interface{} {
|
|||
|
|
//read note 这是一个递归方法，所以递归的结束就是keys最终变成一个值，查找该值，能找到则返回，否则返回nil
|
|||
|
|
if len(keys) == 1 {
|
|||
|
|
if value, ok := m[keys[0]]; ok == true {
|
|||
|
|
return value
|
|||
|
|
}
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 继续进行递归，下一次递归就是往下一个key开始，可以理解就是map一层一层的下去查找对应的key.
|
|||
|
|
if value, ok := m[keys[0]]; ok == true {
|
|||
|
|
if m, ok := value.(map[string]interface{}); ok == true {
|
|||
|
|
return d.findData(m, keys[1:])
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) getKind(val reflect.Value) reflect.Kind {
|
|||
|
|
kind := val.Kind()
|
|||
|
|
|
|||
|
|
switch {
|
|||
|
|
case kind >= reflect.Int && kind <= reflect.Int64:
|
|||
|
|
return reflect.Int
|
|||
|
|
case kind >= reflect.Uint && kind <= reflect.Uint64:
|
|||
|
|
return reflect.Uint
|
|||
|
|
case kind >= reflect.Float32 && kind <= reflect.Float64:
|
|||
|
|
return reflect.Float32
|
|||
|
|
default:
|
|||
|
|
return kind
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// This decodes a basic type (bool, int, string, etc.) and sets the
|
|||
|
|
// value to "data" of that type.
|
|||
|
|
func (d *Decoder) decodeBasic(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
//read note 如果被转换的结果是interface，则只判断是否 AssignableTo
|
|||
|
|
dataVal := reflect.ValueOf(data)
|
|||
|
|
dataValType := dataVal.Type()
|
|||
|
|
if !dataValType.AssignableTo(val.Type()) {
|
|||
|
|
return fmt.Errorf(
|
|||
|
|
"'%s' expected type '%s', got '%s'",
|
|||
|
|
name, val.Type(), dataValType)
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
val.Set(dataVal)
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) decodeString(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
dataVal := reflect.ValueOf(data)
|
|||
|
|
dataKind := d.getKind(dataVal)
|
|||
|
|
|
|||
|
|
//read note string这边的转换规则如下：
|
|||
|
|
// 1、如果被转换的就是string，则直接转换成string
|
|||
|
|
// 开启了弱类型转换标识的
|
|||
|
|
// 2、bool转换从1或0
|
|||
|
|
// 3、数值类型按照十进制转换成字符串
|
|||
|
|
// 4、float类型，按照64位转换
|
|||
|
|
switch {
|
|||
|
|
case dataKind == reflect.String:
|
|||
|
|
val.SetString(dataVal.String())
|
|||
|
|
case dataKind == reflect.Bool && d.config.WeaklyTypedInput:
|
|||
|
|
if dataVal.Bool() {
|
|||
|
|
val.SetString("1")
|
|||
|
|
} else {
|
|||
|
|
val.SetString("0")
|
|||
|
|
}
|
|||
|
|
case dataKind == reflect.Int && d.config.WeaklyTypedInput:
|
|||
|
|
val.SetString(strconv.FormatInt(dataVal.Int(), 10))
|
|||
|
|
case dataKind == reflect.Uint && d.config.WeaklyTypedInput:
|
|||
|
|
val.SetString(strconv.FormatUint(dataVal.Uint(), 10))
|
|||
|
|
case dataKind == reflect.Float32 && d.config.WeaklyTypedInput:
|
|||
|
|
val.SetString(strconv.FormatFloat(dataVal.Float(), 'f', -1, 64))
|
|||
|
|
default:
|
|||
|
|
return fmt.Errorf(
|
|||
|
|
"'%s' expected type '%s', got unconvertible type '%s'",
|
|||
|
|
name, val.Type(), dataVal.Type())
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) decodeInt(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
dataVal := reflect.ValueOf(data)
|
|||
|
|
dataKind := d.getKind(dataVal)
|
|||
|
|
|
|||
|
|
//read note int这边的转换大致如下
|
|||
|
|
// 1、数值类型，直接转换成int，不考虑精度
|
|||
|
|
// 如果开启了弱类型转换标识
|
|||
|
|
// 2、bool类型按照0,1转换
|
|||
|
|
// 3、字符串通过 ParseInt转换
|
|||
|
|
// 4、否则错误
|
|||
|
|
switch {
|
|||
|
|
case dataKind == reflect.Int:
|
|||
|
|
val.SetInt(dataVal.Int())
|
|||
|
|
case dataKind == reflect.Uint:
|
|||
|
|
val.SetInt(int64(dataVal.Uint()))
|
|||
|
|
case dataKind == reflect.Float32:
|
|||
|
|
val.SetInt(int64(dataVal.Float()))
|
|||
|
|
case dataKind == reflect.Bool && d.config.WeaklyTypedInput:
|
|||
|
|
if dataVal.Bool() {
|
|||
|
|
val.SetInt(1)
|
|||
|
|
} else {
|
|||
|
|
val.SetInt(0)
|
|||
|
|
}
|
|||
|
|
case dataKind == reflect.String && d.config.WeaklyTypedInput:
|
|||
|
|
i, err := strconv.ParseInt(dataVal.String(), 0, val.Type().Bits())
|
|||
|
|
if err == nil {
|
|||
|
|
val.SetInt(i)
|
|||
|
|
} else {
|
|||
|
|
return fmt.Errorf("cannot parse '%s' as int: %s", name, err)
|
|||
|
|
}
|
|||
|
|
default:
|
|||
|
|
return fmt.Errorf(
|
|||
|
|
"'%s' expected type '%s', got unconvertible type '%s'",
|
|||
|
|
name, val.Type(), dataVal.Type())
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) decodeUint(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
dataVal := reflect.ValueOf(data)
|
|||
|
|
dataKind := d.getKind(dataVal)
|
|||
|
|
|
|||
|
|
switch {
|
|||
|
|
case dataKind == reflect.Int:
|
|||
|
|
val.SetUint(uint64(dataVal.Int()))
|
|||
|
|
case dataKind == reflect.Uint:
|
|||
|
|
val.SetUint(dataVal.Uint())
|
|||
|
|
case dataKind == reflect.Float32:
|
|||
|
|
val.SetUint(uint64(dataVal.Float()))
|
|||
|
|
case dataKind == reflect.Bool && d.config.WeaklyTypedInput:
|
|||
|
|
if dataVal.Bool() {
|
|||
|
|
val.SetUint(1)
|
|||
|
|
} else {
|
|||
|
|
val.SetUint(0)
|
|||
|
|
}
|
|||
|
|
case dataKind == reflect.String && d.config.WeaklyTypedInput:
|
|||
|
|
i, err := strconv.ParseUint(dataVal.String(), 0, val.Type().Bits())
|
|||
|
|
if err == nil {
|
|||
|
|
val.SetUint(i)
|
|||
|
|
} else {
|
|||
|
|
return fmt.Errorf("cannot parse '%s' as uint: %s", name, err)
|
|||
|
|
}
|
|||
|
|
default:
|
|||
|
|
return fmt.Errorf(
|
|||
|
|
"'%s' expected type '%s', got unconvertible type '%s'",
|
|||
|
|
name, val.Type(), dataVal.Type())
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 入参说明：
|
|||
|
|
// name： 字段名称
|
|||
|
|
// data： 被转换的数据
|
|||
|
|
// val ： 转换最终的结构体
|
|||
|
|
func (d *Decoder) decodeBool(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
dataVal := reflect.ValueOf(data)
|
|||
|
|
dataKind := d.getKind(dataVal)
|
|||
|
|
|
|||
|
|
//read note 这边的转换规则如下：
|
|||
|
|
// 1、bool类型直接转换
|
|||
|
|
// 开启了弱类型转换标识的
|
|||
|
|
// 2、数值类型判断是否为0，0是false
|
|||
|
|
// 3、string类型，先进行bool转换，如果不能转换，空字符表示false，否则错误
|
|||
|
|
// 4、其他类型错误
|
|||
|
|
switch {
|
|||
|
|
case dataKind == reflect.Bool:
|
|||
|
|
val.SetBool(dataVal.Bool())
|
|||
|
|
case dataKind == reflect.Int && d.config.WeaklyTypedInput:
|
|||
|
|
val.SetBool(dataVal.Int() != 0)
|
|||
|
|
case dataKind == reflect.Uint && d.config.WeaklyTypedInput:
|
|||
|
|
val.SetBool(dataVal.Uint() != 0)
|
|||
|
|
case dataKind == reflect.Float32 && d.config.WeaklyTypedInput:
|
|||
|
|
val.SetBool(dataVal.Float() != 0)
|
|||
|
|
case dataKind == reflect.String && d.config.WeaklyTypedInput:
|
|||
|
|
b, err := strconv.ParseBool(dataVal.String())
|
|||
|
|
if err == nil {
|
|||
|
|
val.SetBool(b)
|
|||
|
|
} else if dataVal.String() == "" {
|
|||
|
|
val.SetBool(false)
|
|||
|
|
} else {
|
|||
|
|
return fmt.Errorf("cannot parse '%s' as bool: %s", name, err)
|
|||
|
|
}
|
|||
|
|
default:
|
|||
|
|
return fmt.Errorf(
|
|||
|
|
"'%s' expected type '%s', got unconvertible type '%s'",
|
|||
|
|
name, val.Type(), dataVal.Type())
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) decodeFloat(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
dataVal := reflect.ValueOf(data)
|
|||
|
|
dataKind := d.getKind(dataVal)
|
|||
|
|
|
|||
|
|
switch {
|
|||
|
|
case dataKind == reflect.Int:
|
|||
|
|
val.SetFloat(float64(dataVal.Int()))
|
|||
|
|
case dataKind == reflect.Uint:
|
|||
|
|
val.SetFloat(float64(dataVal.Uint()))
|
|||
|
|
case dataKind == reflect.Float32:
|
|||
|
|
val.SetFloat(float64(dataVal.Float()))
|
|||
|
|
case dataKind == reflect.Bool && d.config.WeaklyTypedInput:
|
|||
|
|
if dataVal.Bool() {
|
|||
|
|
val.SetFloat(1)
|
|||
|
|
} else {
|
|||
|
|
val.SetFloat(0)
|
|||
|
|
}
|
|||
|
|
case dataKind == reflect.String && d.config.WeaklyTypedInput:
|
|||
|
|
f, err := strconv.ParseFloat(dataVal.String(), val.Type().Bits())
|
|||
|
|
if err == nil {
|
|||
|
|
val.SetFloat(f)
|
|||
|
|
} else {
|
|||
|
|
return fmt.Errorf("cannot parse '%s' as float: %s", name, err)
|
|||
|
|
}
|
|||
|
|
default:
|
|||
|
|
return fmt.Errorf(
|
|||
|
|
"'%s' expected type '%s', got unconvertible type '%s'",
|
|||
|
|
name, val.Type(), dataVal.Type())
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 入参说明：
|
|||
|
|
// name： 字段名称
|
|||
|
|
// data： 被转换的数据
|
|||
|
|
// val ： 转换最终的结构体
|
|||
|
|
func (d *Decoder) decodeMap(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
valType := val.Type()
|
|||
|
|
valKeyType := valType.Key()
|
|||
|
|
valElemType := valType.Elem()
|
|||
|
|
|
|||
|
|
// Make a new map to hold our result
|
|||
|
|
//read note 通过反射创建新的map
|
|||
|
|
mapType := reflect.MapOf(valKeyType, valElemType)
|
|||
|
|
valMap := reflect.MakeMap(mapType)
|
|||
|
|
|
|||
|
|
// Check input type
|
|||
|
|
dataVal := reflect.Indirect(reflect.ValueOf(data))
|
|||
|
|
//read note 如果被转换的结构体不是map，这边需要满足
|
|||
|
|
// 1、弱类型标识打开
|
|||
|
|
// 2、空切片或空数组
|
|||
|
|
// 才会返回空map，否则组装错误信息
|
|||
|
|
if dataVal.Kind() != reflect.Map {
|
|||
|
|
// Accept empty array/slice instead of an empty map in weakly typed mode
|
|||
|
|
if d.config.WeaklyTypedInput &&
|
|||
|
|
(dataVal.Kind() == reflect.Slice || dataVal.Kind() == reflect.Array) &&
|
|||
|
|
dataVal.Len() == 0 {
|
|||
|
|
val.Set(valMap)
|
|||
|
|
return nil
|
|||
|
|
} else {
|
|||
|
|
return fmt.Errorf("'%s' expected a map, got '%s'", name, dataVal.Kind())
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Accumulate errors
|
|||
|
|
errors := make([]string, 0)
|
|||
|
|
|
|||
|
|
//read note 遍历被转换结构体的所有key
|
|||
|
|
for _, k := range dataVal.MapKeys() {
|
|||
|
|
fieldName := fmt.Sprintf("%s[%s]", name, k)
|
|||
|
|
|
|||
|
|
// First decode the key into the proper type
|
|||
|
|
//read note 对key进行转换 decode
|
|||
|
|
currentKey := reflect.Indirect(reflect.New(valKeyType))
|
|||
|
|
if err := d.decode(fieldName, k.Interface(), currentKey); err != nil {
|
|||
|
|
errors = appendErrors(errors, err)
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Next decode the data into the proper type
|
|||
|
|
//read note 对value进行转换 decode
|
|||
|
|
v := dataVal.MapIndex(k).Interface()
|
|||
|
|
currentVal := reflect.Indirect(reflect.New(valElemType))
|
|||
|
|
if err := d.decode(fieldName, v, currentVal); err != nil {
|
|||
|
|
errors = appendErrors(errors, err)
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 对结果map进行组装
|
|||
|
|
valMap.SetMapIndex(currentKey, currentVal)
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Set the built up map to the value
|
|||
|
|
//read note map设值
|
|||
|
|
val.Set(valMap)
|
|||
|
|
|
|||
|
|
// If we had errors, return those
|
|||
|
|
if len(errors) > 0 {
|
|||
|
|
return &Error{errors}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) decodeSlice(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
dataVal := reflect.Indirect(reflect.ValueOf(data))
|
|||
|
|
dataValKind := dataVal.Kind()
|
|||
|
|
valType := val.Type()
|
|||
|
|
valElemType := valType.Elem()
|
|||
|
|
|
|||
|
|
// Make a new slice to hold our result, same size as the original data.
|
|||
|
|
//read note 构造新的切片
|
|||
|
|
sliceType := reflect.SliceOf(valElemType)
|
|||
|
|
valSlice := reflect.MakeSlice(sliceType, dataVal.Len(), dataVal.Len())
|
|||
|
|
|
|||
|
|
// Check input type
|
|||
|
|
//read note 同样的弱类型转换，空的map直接返回空数组（弱类型标识为true的情况下）
|
|||
|
|
if dataValKind != reflect.Array && dataValKind != reflect.Slice {
|
|||
|
|
// Accept empty map instead of array/slice in weakly typed mode
|
|||
|
|
if d.config.WeaklyTypedInput && dataVal.Kind() == reflect.Map && dataVal.Len() == 0 {
|
|||
|
|
val.Set(valSlice)
|
|||
|
|
return nil
|
|||
|
|
} else {
|
|||
|
|
return fmt.Errorf(
|
|||
|
|
"'%s': source data must be an array or slice, got %s", name, dataValKind)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Accumulate any errors
|
|||
|
|
errors := make([]string, 0)
|
|||
|
|
|
|||
|
|
//read note 遍历原来的数组，进行每个元素的转换 decode
|
|||
|
|
for i := 0; i < dataVal.Len(); i++ {
|
|||
|
|
currentData := dataVal.Index(i).Interface()
|
|||
|
|
currentField := valSlice.Index(i)
|
|||
|
|
|
|||
|
|
fieldName := fmt.Sprintf("%s[%d]", name, i)
|
|||
|
|
if err := d.decode(fieldName, currentData, currentField); err != nil {
|
|||
|
|
errors = appendErrors(errors, err)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Finally, set the value to the slice we built up
|
|||
|
|
//read note 设置切片的值
|
|||
|
|
val.Set(valSlice)
|
|||
|
|
|
|||
|
|
// If there were errors, we return those
|
|||
|
|
if len(errors) > 0 {
|
|||
|
|
return &Error{errors}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 入参说明：
|
|||
|
|
// name： 字段名称
|
|||
|
|
// data： 被转换的数据
|
|||
|
|
// val ： 转换最终的结构体
|
|||
|
|
func (d *Decoder) decodeStruct(name string, data interface{}, val reflect.Value) error {
|
|||
|
|
dataVal := reflect.Indirect(reflect.ValueOf(data))
|
|||
|
|
dataValKind := dataVal.Kind()
|
|||
|
|
//read note 被转换的类型不是map，错误
|
|||
|
|
if dataValKind != reflect.Map {
|
|||
|
|
return fmt.Errorf("'%s' expected a map, got '%s'", name, dataValKind)
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
dataValType := dataVal.Type()
|
|||
|
|
//read note map的key不是string或者Interface类型，错误
|
|||
|
|
if kind := dataValType.Key().Kind(); kind != reflect.String && kind != reflect.Interface {
|
|||
|
|
return fmt.Errorf("'%s' needs a map with string keys, has '%s' keys", name, dataValType.Key().Kind())
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 这边组装了两个数组，一个是映射成功的key数组，一个是未映射的key数组
|
|||
|
|
dataValKeys, dataValKeysUnused := d.getUseAndUnUseKeyList(dataVal)
|
|||
|
|
|
|||
|
|
// This slice will keep track of all the structs we'll be decoding. There can be more than one struct if there are embedded structs that are squashed.
|
|||
|
|
//read note 正常情况下只会有一个结构体才对，但是这边的处理，如果结构体中的某一个字段是匿名结构体，则会加入到structs中进行处理
|
|||
|
|
// structs[0]是最外层的结构体，structs[1:]是最外层结构体中的匿名字段代表的结构体
|
|||
|
|
structs := make([]reflect.Value, 1, 5)
|
|||
|
|
structs[0] = val
|
|||
|
|
errors := make([]string, 0)
|
|||
|
|
|
|||
|
|
// Compile the list of all the fields that we're going to be decoding from all the structs.
|
|||
|
|
fields := make(map[*reflect.StructField]reflect.Value) //read note 创建【field->value】的map
|
|||
|
|
|
|||
|
|
//read note 循环structs数组，在循环的过程中遇到 【匿名结构体并且标注了squash的结构体字段会加入到structs数组中】
|
|||
|
|
d.structLoopForFieldList(structs, errors, val, fields)
|
|||
|
|
|
|||
|
|
//read note 循环Filed数组，对每一个map能映射到的字段进行赋值（字段名不区分大小写）
|
|||
|
|
d.fieldsLoopForDecode(fields, errors, dataVal, dataValKeys, dataValKeysUnused, name)
|
|||
|
|
|
|||
|
|
//read note errorUnused标识打开，如果map有未转换的可以，则组装错误信息
|
|||
|
|
d.produceErrorWithUnused(dataValKeysUnused, name, errors)
|
|||
|
|
|
|||
|
|
if len(errors) > 0 {
|
|||
|
|
return &Error{errors}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Add the unused keys to the list of unused keys if we're tracking metadata
|
|||
|
|
//read note 组装metadata.这边还要判断name不为空
|
|||
|
|
d.produceMetadata(dataValKeysUnused, name)
|
|||
|
|
|
|||
|
|
return nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) structLoopForFieldList(structs []reflect.Value, errors []string, val reflect.Value, fields map[*reflect.StructField]reflect.Value) {
|
|||
|
|
for len(structs) > 0 {
|
|||
|
|
structVal := structs[0]
|
|||
|
|
structs = structs[1:]
|
|||
|
|
|
|||
|
|
structType := structVal.Type()
|
|||
|
|
//read note 循环结构体的所有Field字段
|
|||
|
|
for i := 0; i < structType.NumField(); i++ {
|
|||
|
|
fieldType := structType.Field(i)
|
|||
|
|
|
|||
|
|
//read note 匿名字段处理
|
|||
|
|
if fieldType.Anonymous {
|
|||
|
|
fieldKind := fieldType.Type.Kind()
|
|||
|
|
//read note 非结构体，错误
|
|||
|
|
if fieldKind != reflect.Struct {
|
|||
|
|
errors = appendErrors(errors,
|
|||
|
|
fmt.Errorf("%s: unsupported type: %s", fieldType.Name, fieldKind))
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// We have an embedded field. We "squash" the fields down
|
|||
|
|
// if specified in the tag.
|
|||
|
|
//read note squash标签只作用在匿名字段上，会对匿名字段结构体的字段进行深入赋值.
|
|||
|
|
squash := false
|
|||
|
|
tagParts := strings.Split(fieldType.Tag.Get(d.config.TagName), ",")
|
|||
|
|
for _, tag := range tagParts[1:] {
|
|||
|
|
if tag == "squash" {
|
|||
|
|
squash = true
|
|||
|
|
break
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 如果是squash标签标识，会加入到structs数组中，在下一次循环开始之前进行循环
|
|||
|
|
if squash {
|
|||
|
|
structs = append(structs, val.FieldByName(fieldType.Name))
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Normal struct field, store it away
|
|||
|
|
//read note 组装map指向
|
|||
|
|
fields[&fieldType] = structVal.Field(i)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) fieldsLoopForDecode(fields map[*reflect.StructField]reflect.Value, errors []string, dataVal reflect.Value, dataValKeys map[reflect.Value]struct{}, dataValKeysUnused map[interface{}]struct{}, name string) {
|
|||
|
|
//read note 循环所有的Field，这边的field数组可能是当前结构体的，也可能是结构体中的匿名字段的field
|
|||
|
|
for fieldType, field := range fields {
|
|||
|
|
fieldName := fieldType.Name
|
|||
|
|
|
|||
|
|
//read note 获取tag标签，进行【,】切割，这边的标识默认是 mapstructure，比如说 mapstructure：name.获取的就是name
|
|||
|
|
tagValue := fieldType.Tag.Get(d.config.TagName)
|
|||
|
|
tagValue = strings.SplitN(tagValue, ",", 2)[0]
|
|||
|
|
if tagValue != "" {
|
|||
|
|
fieldName = tagValue
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 根据key获取map中的值
|
|||
|
|
rawMapKey := reflect.ValueOf(fieldName)
|
|||
|
|
rawMapVal := dataVal.MapIndex(rawMapKey)
|
|||
|
|
//read note 循环Key数组，进行大小写不敏感匹配，获得map中可以，对应的value
|
|||
|
|
if !rawMapVal.IsValid() {
|
|||
|
|
// Do a slower search by iterating over each key and
|
|||
|
|
// doing case-insensitive search.
|
|||
|
|
for dataValKey, _ := range dataValKeys {
|
|||
|
|
mK, ok := dataValKey.Interface().(string)
|
|||
|
|
if !ok {
|
|||
|
|
// Not a string key
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 不区分大小写
|
|||
|
|
if strings.EqualFold(mK, fieldName) {
|
|||
|
|
rawMapKey = dataValKey
|
|||
|
|
rawMapVal = dataVal.MapIndex(dataValKey)
|
|||
|
|
break
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
if !rawMapVal.IsValid() {
|
|||
|
|
// There was no matching key in the map for the value in
|
|||
|
|
// the struct. Just ignore.
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Delete the key we're using from the unused map so we stop tracking
|
|||
|
|
//read note 未使用的key数组把被转换的key删掉
|
|||
|
|
delete(dataValKeysUnused, rawMapKey.Interface())
|
|||
|
|
|
|||
|
|
//read note 非IsValid直接报错
|
|||
|
|
if !field.IsValid() {
|
|||
|
|
// This should never happen
|
|||
|
|
panic("field is not valid")
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// If we can't set the field, then it is unexported or something,
|
|||
|
|
// and we just continue onwards.
|
|||
|
|
if !field.CanSet() {
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// If the name is empty string, then we're at the root, and we
|
|||
|
|
// don't dot-join the fields.
|
|||
|
|
if name != "" {
|
|||
|
|
fieldName = fmt.Sprintf("%s.%s", name, fieldName)
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
//read note 字段再递归进去处理，可能是对应的不同的类型
|
|||
|
|
if err := d.decode(fieldName, rawMapVal.Interface(), field); err != nil {
|
|||
|
|
errors = appendErrors(errors, err)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) produceErrorWithUnused(dataValKeysUnused map[interface{}]struct{}, name string, errors []string) {
|
|||
|
|
if d.config.ErrorUnused && len(dataValKeysUnused) > 0 {
|
|||
|
|
keys := make([]string, 0, len(dataValKeysUnused))
|
|||
|
|
for rawKey, _ := range dataValKeysUnused {
|
|||
|
|
keys = append(keys, rawKey.(string))
|
|||
|
|
}
|
|||
|
|
sort.Strings(keys)
|
|||
|
|
|
|||
|
|
err := fmt.Errorf("'%s' has invalid keys: %s", name, strings.Join(keys, ", "))
|
|||
|
|
errors = appendErrors(errors, err)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) produceMetadata(dataValKeysUnused map[interface{}]struct{}, name string) {
|
|||
|
|
if d.config.Metadata != nil {
|
|||
|
|
for rawKey, _ := range dataValKeysUnused {
|
|||
|
|
key := rawKey.(string)
|
|||
|
|
if name != "" {
|
|||
|
|
key = fmt.Sprintf("%s.%s", name, key)
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
d.config.Metadata.Unused = append(d.config.Metadata.Unused, key)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (d *Decoder) getUseAndUnUseKeyList(dataVal reflect.Value) (map[reflect.Value]struct{}, map[interface{}]struct{}) {
|
|||
|
|
dataValKeys := make(map[reflect.Value]struct{})
|
|||
|
|
dataValKeysUnused := make(map[interface{}]struct{})
|
|||
|
|
//read note 循环map的key，组装key数组和未使用的key数组
|
|||
|
|
for _, dataValKey := range dataVal.MapKeys() {
|
|||
|
|
dataValKeys[dataValKey] = struct{}{}
|
|||
|
|
dataValKeysUnused[dataValKey.Interface()] = struct{}{}
|
|||
|
|
}
|
|||
|
|
return dataValKeys, dataValKeysUnused
|
|||
|
|
}
|