聊聊dubbo-go-proxy的jtypes

Posted 2021-10-05 codecraft

序

本文主要研究一下dubbo-go-proxy的jtypes

JTypeMapper

dubbo-go-proxy/pkg/common/constant/jtypes.go

// Object represents the java.lang.Object type
type Object interface{}

// JTypeMapper maps the java basic types to golang types
var JTypeMapper = map[string]reflect.Type{
    "string":           reflect.TypeOf(""),
    "java.lang.String": reflect.TypeOf(""),
    "char":             reflect.TypeOf(""),
    "short":            reflect.TypeOf(int32(0)),
    "int":              reflect.TypeOf(int32(0)),
    "long":             reflect.TypeOf(int64(0)),
    "float":            reflect.TypeOf(float64(0)),
    "double":           reflect.TypeOf(float64(0)),
    "boolean":          reflect.TypeOf(true),
    "java.util.Date":   reflect.TypeOf(time.Time{}),
    "date":             reflect.TypeOf(time.Time{}),
    "object":           reflect.TypeOf([]Object{}).Elem(),
    "java.lang.Object": reflect.TypeOf([]Object{}).Elem(),
}

JTypeMapper定义了个map，key为java类型，value为golang的reflect.Type

mapTypes

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

func mapTypes(jType string, originVal interface{}) (interface{}, error) {
    targetType, ok := constant.JTypeMapper[jType]
    if !ok {
        return nil, errors.Errorf("Invalid parameter type: %s", jType)
    }
    switch targetType {
    case reflect.TypeOf(""):
        return cast.ToStringE(originVal)
    case reflect.TypeOf(int32(0)):
        return cast.ToInt32E(originVal)
    case reflect.TypeOf(int64(0)):
        return cast.ToInt64E(originVal)
    case reflect.TypeOf(float64(0)):
        return cast.ToFloat64E(originVal)
    case reflect.TypeOf(true):
        return cast.ToBoolE(originVal)
    case reflect.TypeOf(time.Time{}):
        return cast.ToBoolE(originVal)
    default:
        return originVal, nil
    }
}

mapTypes方法先根据jType从JTypeMapper取出对应的golang的reflect.Type，然后挨个根据这个类型使用cast类库进行转换，转成golang的interface{}

caste.go

github.com/spf13/cast@v1.3.1/caste.go

// ToStringE casts an interface to a string type.
func ToStringE(i interface{}) (string, error) {
    i = indirectToStringerOrError(i)

    switch s := i.(type) {
    case string:
        return s, nil
    case bool:
        return strconv.FormatBool(s), nil
    case float64:
        return strconv.FormatFloat(s, \'f\', -1, 64), nil
    case float32:
        return strconv.FormatFloat(float64(s), \'f\', -1, 32), nil
    case int:
        return strconv.Itoa(s), nil
    case int64:
        return strconv.FormatInt(s, 10), nil
    case int32:
        return strconv.Itoa(int(s)), nil
    case int16:
        return strconv.FormatInt(int64(s), 10), nil
    case int8:
        return strconv.FormatInt(int64(s), 10), nil
    case uint:
        return strconv.FormatUint(uint64(s), 10), nil
    case uint64:
        return strconv.FormatUint(uint64(s), 10), nil
    case uint32:
        return strconv.FormatUint(uint64(s), 10), nil
    case uint16:
        return strconv.FormatUint(uint64(s), 10), nil
    case uint8:
        return strconv.FormatUint(uint64(s), 10), nil
    case []byte:
        return string(s), nil
    case template.html:
        return string(s), nil
    case template.URL:
        return string(s), nil
    case template.JS:
        return string(s), nil
    case template.CSS:
        return string(s), nil
    case template.HTMLAttr:
        return string(s), nil
    case nil:
        return "", nil
    case fmt.Stringer:
        return s.String(), nil
    case error:
        return s.Error(), nil
    default:
        return "", fmt.Errorf("unable to cast %#v of type %T to string", i, i)
    }
}

github.com/spf13/cast提供了一系列的cast方法，用于将interface{}转换为指定的类型

小结

JTypeMapper定义了个map，key为java类型，value为golang的reflect.Type；mapTypes方法先根据jType从JTypeMapper取出对应的golang的reflect.Type，然后挨个根据这个类型使用cast类库进行转换，转成golang的interface{}。

doc

• dubbo-go-proxy