英文:
Golang unmarshal XML attribute into interface
问题
我正在尝试将一些XML解组成一个具有interface{}类型的结构体。然而,无论我如何运行代码,它都没有解析出任何内容。所有其他元素似乎都正常工作,如果我将类型设置为string或[]byte,它将正常工作,但是我需要它更加灵活。
我感兴趣的元素位于第32行 - FloorRefID。
以下是XML示例:
<?xml version="1.0" encoding="UTF-8"?>
<Locations totalPages="1" currentPage="1" pageSize="25">
<WirelessClientLocation macAddress="00:00:00:00:00:00">
<MapInfo mapHierarchyString="Head office>Ground floor>Store" floorRefId="-1122334455667789">
<Image imageName="floorPlan1.png" />
</MapInfo>
<MapCoordinate x="2850" y="3000" unit="FEET" />
</WirelessClientLocation>
<WirelessClientLocation macAddress="11:11:11:11:11:11">
<MapInfo mapHierarchyString="Head office>Ground floor>Store" floorRefId="-1122334455667789">
<Image imageName="floorPlan1.png" />
</MapInfo>
<MapCoordinate x="10.72" y="76.49" unit="FEET" />
</WirelessClientLocation>
<WirelessClientLocation macAddress="26:cd:96:46:0b:2b">
<MapInfo floorRefId="0" />
<MapCoordinate x="51.52" y="4.2" unit="FEET" />
</WirelessClientLocation>
</Locations>
为了提供一些背景信息:我正在与一个供应商集成的项目上工作,有时我们会收到XML格式的数据,有时是JSON格式的数据。我希望构建一个可以解组两种格式的结构体的工具,而不是复制相同结构的代码。这个结构体有很多子结构,这意味着如果要保持两个几乎相同的结构体,除了这个属性之外,需要做很多工作。
当我们收到JSON数据时,该字段可以是字符串或数字。
我了解到不能将数据解组到interface{}类型中,但是否有人知道如何解决我这种情况的问题呢?
英文:
I'm trying to unmarshal some XML into a structure with an interface{} type. However whenever I try to run it, the code doesn't pick up anything at all. All of the other elements appear to work fine, and if I set the type to string or []byte it will work, however I need it to be more flexible than that.
The element I am interested in is on <b>line 32</b> - <b>FloorRefID</b>
https://play.golang.org/p/Ehr8qx1aWf
<?xml version="1.0" encoding="UTF-8"?>
<Locations totalPages="1" currentPage="1" pageSize="25">
<WirelessClientLocation macAddress="00:00:00:00:00:00">
<MapInfo mapHierarchyString="Head office&gt;Ground floor&gt;Store" floorRefId="-1122334455667789">
<Image imageName="floorPlan1.png" />
</MapInfo>
<MapCoordinate x="2850" y="3000" unit="FEET" />
</WirelessClientLocation>
<WirelessClientLocation macAddress="11:11:11:11:11:11">
<MapInfo mapHierarchyString="Head office&gt;Ground floor&gt;Store" floorRefId="-1122334455667789">
<Image imageName="floorPlan1.png" />
</MapInfo>
<MapCoordinate x="10.72" y="76.49" unit="FEET" />
</WirelessClientLocation>
<WirelessClientLocation macAddress="26:cd:96:46:0b:2b">
<MapInfo floorRefId="0" />
<MapCoordinate x="51.52" y="4.2" unit="FEET" />
</WirelessClientLocation>
</Locations>
To give some context; I am working on a project integrating with a vendor in which sometimes we receive the data as XML and sometimes as JSON. I wanted to build something that could unmarshal the structure for both, rather than duplicating the structure set. It has many substructures which means that its a lot more work to keep 2 structures which are almost identical except for this one attribute.
When we receive the JSON data, the field can be given as a string or a number.
I have read that you cannot unmarshal into an interface, but does anyone know of a way around this issue for my scenario?
答案1
得分: 5
检查返回的错误总是很重要。
if err := xml.Unmarshal([]byte(xmlRawData), &xmlData); err != nil {
fmt.Println(err)
}
你得到的错误是:
cannot unmarshal into interface {}
空接口无法进行解组,因为空接口没有任何导出字段来映射 XML 键/值。
然而,有一种方法可以解决这个问题。在你的 VendorMapInfo
结构体上实现 xml.Unmarshaler 接口。
示例:更新后的代码
type VendorMapInfo struct {
MapHierarchyString string `xml:"mapHierarchyString,attr"`
FloorRefID interface{} `xml:"floorRefId,attr"`
Image Image `xml:"Image"`
FloorDimension VendorFloorDimension
}
type Image struct {
Name string `xml:"imageName,attr"`
}
func (mf *VendorMapInfo) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
// Attributes
for _, attr := range start.Attr {
switch attr.Name.Local {
case "mapHierarchyString":
mf.MapHierarchyString = attr.Value
case "floorRefId":
mf.FloorRefID = findFloorRefIDType(attr.Value)
}
}
for {
token, err := d.Token()
if err != nil {
return err
}
switch el := token.(type) {
case xml.StartElement:
if el.Name.Local == "Image" {
item := new(Image)
if err = d.DecodeElement(item, &el); err != nil {
return err
}
mf.Image = *item
}
case xml.EndElement:
if el == start.End() {
return nil
}
}
}
return nil
}
完整代码,Playground 链接:https://play.golang.org/p/wZQOsQv0Nq
输出:
{Locations:{Space: Local:} WirelessClientLocation:[{MacAddress:00:00:00:00:00:00 MapInfo:{MapHierarchyString:Head office>Ground floor>Store FloorRefID:-1122334455667789 Image:{Name:floorPlan1.png} FloorDimension:{Length:0 Width:0 Height:0 OffsetX:0 OffsetY:0 Unit:}}} {MacAddress:11:11:11:11:11:11 MapInfo:{MapHierarchyString:Head office>Ground floor>Store FloorRefID:-1122334455667789 Image:{Name:floorPlan1.png} FloorDimension:{Length:0 Width:0 Height:0 OffsetX:0 OffsetY:0 Unit:}}} {MacAddress:26:cd:96:46:0b:2b MapInfo:{MapHierarchyString: FloorRefID:0 Image:{Name:} FloorDimension:{Length:0 Width:0 Height:0 OffsetX:0 OffsetY:0 Unit:}}}]}
[1]: https://golang.org/pkg/encoding/xml/#Unmarshaler
英文:
Its important to check the returned error always.
if err := xml.Unmarshal([]byte(xmlRawData), &xmlData); err != nil {
fmt.Println(err)
}
The error you're getting is
cannot unmarshal into interface {}
Empty interface cannot be unmarshalled since the empty interface doesn't have any exported fields to map the xml keys/values to.
However there is way to get around. Implementing xml.Unmarshaler interface on your VendorMapInfo
struct.
Example: Your updated code
type VendorMapInfo struct {
MapHierarchyString string `xml:"mapHierarchyString,attr"`
FloorRefID interface{} `xml:"floorRefId,attr"`
Image Image `xml:"Image"`
FloorDimension VendorFloorDimension
}
type Image struct {
Name string `xml:"imageName,attr"`
}
func (mf *VendorMapInfo) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
// Attributes
for _, attr := range start.Attr {
switch attr.Name.Local {
case "mapHierarchyString":
mf.MapHierarchyString = attr.Value
case "floorRefId":
mf.FloorRefID = findFloorRefIDType(attr.Value)
}
}
for {
token, err := d.Token()
if err != nil {
return err
}
switch el := token.(type) {
case xml.StartElement:
if el.Name.Local == "Image" {
item := new(Image)
if err = d.DecodeElement(item, &el); err != nil {
return err
}
mf.Image = *item
}
case xml.EndElement:
if el == start.End() {
return nil
}
}
}
return nil
}
Complete code, play link: https://play.golang.org/p/wZQOsQv0Nq
Output:
{Locations:{Space: Local:} WirelessClientLocation:[{MacAddress:00:00:00:00:00:00 MapInfo:{MapHierarchyString:Head office>Ground floor>Store FloorRefID:-1122334455667789 Image:{Name:floorPlan1.png} FloorDimension:{Length:0 Width:0 Height:0 OffsetX:0 OffsetY:0 Unit:}}} {MacAddress:11:11:11:11:11:11 MapInfo:{MapHierarchyString:Head office>Ground floor>Store FloorRefID:-1122334455667789 Image:{Name:floorPlan1.png} FloorDimension:{Length:0 Width:0 Height:0 OffsetX:0 OffsetY:0 Unit:}}} {MacAddress:26:cd:96:46:0b:2b MapInfo:{MapHierarchyString: FloorRefID:0 Image:{Name:} FloorDimension:{Length:0 Width:0 Height:0 OffsetX:0 OffsetY:0 Unit:}}}]}
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