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build.go
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build.go
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// Package xmlutil provides XML serialization of AWS requests and responses.
package xmlutil
import (
"encoding/base64"
"encoding/xml"
"fmt"
"reflect"
"sort"
"strconv"
"time"
"github.com/aws/aws-sdk-go/private/protocol"
)
// BuildXML will serialize params into an xml.Encoder. Error will be returned
// if the serialization of any of the params or nested values fails.
func BuildXML(params interface{}, e *xml.Encoder) error {
return buildXML(params, e, false)
}
func buildXML(params interface{}, e *xml.Encoder, sorted bool) error {
b := xmlBuilder{encoder: e, namespaces: map[string]string{}}
root := NewXMLElement(xml.Name{})
if err := b.buildValue(reflect.ValueOf(params), root, ""); err != nil {
return err
}
for _, c := range root.Children {
for _, v := range c {
return StructToXML(e, v, sorted)
}
}
return nil
}
// Returns the reflection element of a value, if it is a pointer.
func elemOf(value reflect.Value) reflect.Value {
for value.Kind() == reflect.Ptr {
value = value.Elem()
}
return value
}
// A xmlBuilder serializes values from Go code to XML
type xmlBuilder struct {
encoder *xml.Encoder
namespaces map[string]string
}
// buildValue generic XMLNode builder for any type. Will build value for their specific type
// struct, list, map, scalar.
//
// Also takes a "type" tag value to set what type a value should be converted to XMLNode as. If
// type is not provided reflect will be used to determine the value's type.
func (b *xmlBuilder) buildValue(value reflect.Value, current *XMLNode, tag reflect.StructTag) error {
value = elemOf(value)
if !value.IsValid() { // no need to handle zero values
return nil
} else if tag.Get("location") != "" { // don't handle non-body location values
return nil
}
t := tag.Get("type")
if t == "" {
switch value.Kind() {
case reflect.Struct:
t = "structure"
case reflect.Slice:
t = "list"
case reflect.Map:
t = "map"
}
}
switch t {
case "structure":
if field, ok := value.Type().FieldByName("_"); ok {
tag = tag + reflect.StructTag(" ") + field.Tag
}
return b.buildStruct(value, current, tag)
case "list":
return b.buildList(value, current, tag)
case "map":
return b.buildMap(value, current, tag)
default:
return b.buildScalar(value, current, tag)
}
}
// buildStruct adds a struct and its fields to the current XMLNode. All fields any any nested
// types are converted to XMLNodes also.
func (b *xmlBuilder) buildStruct(value reflect.Value, current *XMLNode, tag reflect.StructTag) error {
if !value.IsValid() {
return nil
}
fieldAdded := false
// unwrap payloads
if payload := tag.Get("payload"); payload != "" {
field, _ := value.Type().FieldByName(payload)
tag = field.Tag
value = elemOf(value.FieldByName(payload))
if !value.IsValid() {
return nil
}
}
child := NewXMLElement(xml.Name{Local: tag.Get("locationName")})
// there is an xmlNamespace associated with this struct
if prefix, uri := tag.Get("xmlPrefix"), tag.Get("xmlURI"); uri != "" {
ns := xml.Attr{
Name: xml.Name{Local: "xmlns"},
Value: uri,
}
if prefix != "" {
b.namespaces[prefix] = uri // register the namespace
ns.Name.Local = "xmlns:" + prefix
}
child.Attr = append(child.Attr, ns)
}
t := value.Type()
for i := 0; i < value.NumField(); i++ {
member := elemOf(value.Field(i))
field := t.Field(i)
if field.PkgPath != "" {
continue // ignore unexported fields
}
if field.Tag.Get("ignore") != "" {
continue
}
mTag := field.Tag
if mTag.Get("location") != "" { // skip non-body members
continue
}
if protocol.CanSetIdempotencyToken(value.Field(i), field) {
token := protocol.GetIdempotencyToken()
member = reflect.ValueOf(token)
}
memberName := mTag.Get("locationName")
if memberName == "" {
memberName = field.Name
mTag = reflect.StructTag(string(mTag) + ` locationName:"` + memberName + `"`)
}
if err := b.buildValue(member, child, mTag); err != nil {
return err
}
fieldAdded = true
}
if fieldAdded { // only append this child if we have one ore more valid members
current.AddChild(child)
}
return nil
}
// buildList adds the value's list items to the current XMLNode as children nodes. All
// nested values in the list are converted to XMLNodes also.
func (b *xmlBuilder) buildList(value reflect.Value, current *XMLNode, tag reflect.StructTag) error {
if value.IsNil() { // don't build omitted lists
return nil
}
// check for unflattened list member
flattened := tag.Get("flattened") != ""
xname := xml.Name{Local: tag.Get("locationName")}
if flattened {
for i := 0; i < value.Len(); i++ {
child := NewXMLElement(xname)
current.AddChild(child)
if err := b.buildValue(value.Index(i), child, ""); err != nil {
return err
}
}
} else {
list := NewXMLElement(xname)
current.AddChild(list)
for i := 0; i < value.Len(); i++ {
iname := tag.Get("locationNameList")
if iname == "" {
iname = "member"
}
child := NewXMLElement(xml.Name{Local: iname})
list.AddChild(child)
if err := b.buildValue(value.Index(i), child, ""); err != nil {
return err
}
}
}
return nil
}
// buildMap adds the value's key/value pairs to the current XMLNode as children nodes. All
// nested values in the map are converted to XMLNodes also.
//
// Error will be returned if it is unable to build the map's values into XMLNodes
func (b *xmlBuilder) buildMap(value reflect.Value, current *XMLNode, tag reflect.StructTag) error {
if value.IsNil() { // don't build omitted maps
return nil
}
maproot := NewXMLElement(xml.Name{Local: tag.Get("locationName")})
current.AddChild(maproot)
current = maproot
kname, vname := "key", "value"
if n := tag.Get("locationNameKey"); n != "" {
kname = n
}
if n := tag.Get("locationNameValue"); n != "" {
vname = n
}
// sorting is not required for compliance, but it makes testing easier
keys := make([]string, value.Len())
for i, k := range value.MapKeys() {
keys[i] = k.String()
}
sort.Strings(keys)
for _, k := range keys {
v := value.MapIndex(reflect.ValueOf(k))
mapcur := current
if tag.Get("flattened") == "" { // add "entry" tag to non-flat maps
child := NewXMLElement(xml.Name{Local: "entry"})
mapcur.AddChild(child)
mapcur = child
}
kchild := NewXMLElement(xml.Name{Local: kname})
kchild.Text = k
vchild := NewXMLElement(xml.Name{Local: vname})
mapcur.AddChild(kchild)
mapcur.AddChild(vchild)
if err := b.buildValue(v, vchild, ""); err != nil {
return err
}
}
return nil
}
// buildScalar will convert the value into a string and append it as a attribute or child
// of the current XMLNode.
//
// The value will be added as an attribute if tag contains a "xmlAttribute" attribute value.
//
// Error will be returned if the value type is unsupported.
func (b *xmlBuilder) buildScalar(value reflect.Value, current *XMLNode, tag reflect.StructTag) error {
var str string
switch converted := value.Interface().(type) {
case string:
str = converted
case []byte:
if !value.IsNil() {
str = base64.StdEncoding.EncodeToString(converted)
}
case bool:
str = strconv.FormatBool(converted)
case int64:
str = strconv.FormatInt(converted, 10)
case int:
str = strconv.Itoa(converted)
case float64:
str = strconv.FormatFloat(converted, 'f', -1, 64)
case float32:
str = strconv.FormatFloat(float64(converted), 'f', -1, 32)
case time.Time:
const ISO8601UTC = "2006-01-02T15:04:05Z"
str = converted.UTC().Format(ISO8601UTC)
default:
return fmt.Errorf("unsupported value for param %s: %v (%s)",
tag.Get("locationName"), value.Interface(), value.Type().Name())
}
xname := xml.Name{Local: tag.Get("locationName")}
if tag.Get("xmlAttribute") != "" { // put into current node's attribute list
attr := xml.Attr{Name: xname, Value: str}
current.Attr = append(current.Attr, attr)
} else { // regular text node
current.AddChild(&XMLNode{Name: xname, Text: str})
}
return nil
}