聊聊dubbo-go-proxy的ParamMapper-木庄网络博客

本文摘自网络，作者，侵删。

序

本文主要研究一下dubbo-go-proxy的ParamMapper

ParamMapper

dubbo-go-proxy/pkg/client/mapper.go

// ParamMapper defines the interface about how to map the params in the inbound request.
type ParamMapper interface {
    // Map implements how the request parameters map to the target parameters described by config.MappingParam
    Map(config.MappingParam, *Request, interface{}, RequestOption) error
}

ParamMapper接口定义了Map方法

headerMapper

dubbo-go-proxy/pkg/client/http/mapper.go

type headerMapper struct{}

// nolint
func (hm headerMapper) Map(mp config.MappingParam, c *client.Request, rawTarget interface{}, option client.RequestOption) error {
    target, fromKey, to, toKey, err := mapPrepare(mp, rawTarget)
    if err != nil {
        return err
    }

    rawHeader := c.IngressRequest.Header.Get(fromKey[0])
    if len(rawHeader) == 0 {
        return errors.Errorf("Header %s not found", fromKey[0])
    }
    setTarget(target, to, toKey[0], rawHeader)
    return nil
}

headerMapper实现了ParamMapper接口，其Map方法提取和映射header

uriMapper

dubbo-go-proxy/pkg/client/http/mapper.go

type uriMapper struct{}

func (um uriMapper) Map(mp config.MappingParam, c *client.Request, rawTarget interface{}, option client.RequestOption) error {
    target, fromKey, to, toKey, err := mapPrepare(mp, rawTarget)
    if err != nil {
        return err
    }
    if to == constant.RequestURI {

    }
    uriValues := router.GetURIParams(&c.API, *c.IngressRequest.URL)
    if uriValues == nil {
        return errors.New("No URI parameters found")
    }
    setTarget(target, to, strings.Join(toKey, constant.Dot), uriValues.Get(fromKey[0]))
    return nil
}

uriMapper实现了ParamMapper接口，其Map方法用于提取和映射uri

queryStringsMapper

dubbo-go-proxy/pkg/client/http/mapper.go

type queryStringsMapper struct{}

// nolint
func (qs queryStringsMapper) Map(mp config.MappingParam, c *client.Request, rawTarget interface{}, option client.RequestOption) error {
    target, fromKey, to, toKey, err := mapPrepare(mp, rawTarget)
    if err != nil {
        return err
    }
    queryValues, err := url.ParseQuery(c.IngressRequest.URL.RawQuery)
    if err != nil {
        return errors.Wrap(err, "Error happened when parsing the query paramters")
    }
    rawValue := queryValues.Get(fromKey[0])
    if len(rawValue) == 0 {
        return errors.Errorf("%s in query parameters not found", fromKey[0])
    }
    setTarget(target, to, toKey[0], rawValue)
    return nil
}

queryStringsMapper实现了ParamMapper接口，其Map方法用于提取和映射query string

bodyMapper

dubbo-go-proxy/pkg/client/http/mapper.go

type bodyMapper struct{}

// nolint
func (bm bodyMapper) Map(mp config.MappingParam, c *client.Request, rawTarget interface{}, option client.RequestOption) error {
    // TO-DO: add support for content-type other than application/json
    target, fromKey, to, toKey, err := mapPrepare(mp, rawTarget)
    if err != nil {
        return err
    }

    rawBody, err := ioutil.ReadAll(c.IngressRequest.Body)
    defer func() {
        c.IngressRequest.Body = ioutil.NopCloser(bytes.NewReader(rawBody))
    }()
    if err != nil {
        return err
    }
    mapBody := map[string]interface{}{}
    json.Unmarshal(rawBody, &mapBody)
    val, err := client.GetMapValue(mapBody, fromKey)
    if err != nil {
        return errors.Wrapf(err, "Error when get body value from key %s", fromKey)
    }
    setTarget(target, to, strings.Join(toKey, constant.Dot), val)
    return nil
}

bodyMapper实现了ParamMapper接口，其Map方法用于提取和映射body参数

mapPrepare

dubbo-go-proxy/pkg/client/http/mapper.go

func mapPrepare(mp config.MappingParam, rawTarget interface{}) (target *requestParams, fromKey []string, to string, toKey []string, err error) {
    // ensure the target is a pointer and type is requestParams
    target, err = validateTarget(rawTarget)
    if err != nil {
        return nil, nil, "", nil, err
    }
    // retrieve the mapping values' origin param name
    _, fromKey, err = client.ParseMapSource(mp.Name)
    if err != nil {
        return nil, nil, "", nil, err
    }
    // retrieve the mapping values' target param name and param types(header/uri/query/request body)
    to, toKey, err = client.ParseMapSource(mp.MapTo)
    if err != nil {
        return nil, nil, "", nil, err
    }
    return target, fromKey, to, toKey, nil
}

mapPrepare方法根据config.MappingParam从rawTarget提取requestParams、fromKey、to、toKey

setTarget

dubbo-go-proxy/pkg/client/http/mapper.go

func setTarget(target *requestParams, to string, key string, val interface{}) error {
    valType := reflect.TypeOf(val)
    if (to == constant.Headers || to == constant.QueryStrings) && valType.Kind() != reflect.String {
        return errors.Errorf("%s only accepts string", to)
    }
    switch to {
    case constant.Headers:
        target.Header.Set(key, val.(string))
    case constant.RequestURI:
        target.URIParams.Set(key, val.(string))
    case constant.QueryStrings:
        target.Query.Set(key, val.(string))
    case constant.RequestBody:
        rawBody, err := ioutil.ReadAll(target.Body)
        defer func() {
            target.Body = ioutil.NopCloser(bytes.NewReader(rawBody))
        }()
        if err != nil {
            return errors.New("Raw body parse failed")
        }
        mapBody := map[string]interface{}{}
        json.Unmarshal(rawBody, &mapBody)

        setMapWithPath(mapBody, key, val)
        rawBody, err = json.Marshal(mapBody)
        if err != nil {
            return errors.New("Stringify map to body failed")
        }
    default:
        return errors.Errorf("Mapping target to %s does not support", to)
    }
    return nil
}

setTarget方法用于将val写入到requestParams的对应部分

小结

dubbo-go-proxy的ParamMapper接口定义了Map方法；它有四个实现类分别是headerMapper、uriMapper、queryStringsMapper、bodyMapper；mapPrepare方法用于提取参数，setTarget方法用于将val写入到requestParams的对应部分。