用Go的xml软件包编组DIDL-Lite [英] Marshalling DIDL-Lite with Go's xml package

问题描述

以下是一个 DIDL-Lite XML文档示例 UPnP AV ContentDirectory v2服务模板：

 <？xml version =1.0encoding =UTF-8？ > 
< DIDL-Lite 
 xmlns：dc =http://purl.org/dc/elements/1.1/
 xmlns =urn：schemas-upnp-org：metadata- 1-0 / DIDL-Lite /
 xmlns：upnp =urn：schemas-upnp-org：metadata-1-0 / upnp /
 xmlns：xsi =http：// www。 w3.org/2001/XMLSchema-instance
 xsi：schemaLocation =
 urn：schemas-upnp-org：metadata-1-0 / DIDL-Lite / 
 http：// www .upnp.org / schemas / av / didl-lite-v2-20060531.xsd 
 urn：schemas-upnp-org：metadata-1-0 / upnp / 
 http：//www.upnp。组织/模式/ AV / UPnP的v2-20061231.xsd> 
< item id =18parentID =13restricted =0> 
 ... 
< / item> 
< / DIDL-Lite> 
  

如何使用编组 http://golang.org/pkg/encoding/xml/rel =nofollow> Go的xml包？更具体地说：

1. 定义名称空间前缀的方式，比如 xmlns：dc 和 xmlns：upnp ？


2. 如何在元素上配置多个名称空间？是为属性设置的名称空间，例如 schemaLocation 属性中的 xsi 前缀





作为一个基地，我有这样的事情：

  type DIDLLite struct {
 XMLName xml.Name`xml：urn：schemas-upnp-org：metadata-1-0 / DIDL-Lite / DIDL-Lite`
 // ???命名空间前缀dc，upnp，xsi 
 Objects [] Object 
} 
  

I还发现了此可能存在的相关错误。

解决方案

您给的例子是。我假设你的意思是要问，如何定义用xml.Marshal编组的Go数据类型到这里？



  package 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 $ b $ .name 
 DC string`xml：xmlns：dc，attr`
 UPNP string`xml：xmlns：upnp，attr`
 XSI string`xml：xmlns：xsi， attr`
 XLOC string`xml：xsi：schemaLocation，attr`
 Objects [] Object`xml：item`
} 
 
 type Object struct {
 ID字符串`xml：id，attr`
父字符串`xml：parentID，attr`
受限字符串`xml：restricted，attr`
 
 
 func main（）{
d：= DIDLLite {
 XMLName：xml.Name {
空格：urn：schemas-upnp-org：metadata- 1-0 / DIDL-Lite /，
本地：DIDL-Lite，
}，
 DC：http://purl.org/dc/elements/1.1/ ，
 UPNP：urn：schemas-upnp -org：metadata-1-0 / upnp /，
 XSI：http://www.w3.org/2001/XMLSchema-instance，
 XLOC：`
 urn： schema-upnp-org：metadata-1-0 / DIDL-Lite / 
 http://www.upnp.org/schemas/av/didl-lite-v2-20060531.xsd 
 urn：模式-upnp-org：metadata-1-0 / upnp / 
 http：// www.upnp.org/ schemas / av / upnp-v2-20061231.xsd`，
对象：[] Object { {ID：18，Parent：13，Restricted：0}}，
} 
b，err：= xml.MarshalIndent（d，，）
如果err！= nil {
 fmt.Println（err）
 return 
} 
 fmt.Println（string（b））
} 
 < 
 
 
 
 
 $ b $ ; DIDL-Lite xmlns =urn：schemas-upnp-org：metadata-1-0 / DIDL-Lite /xmlns：dc =http://purl.org/dc/elements/1.1/xmlns：upnp = urn：schemas-upnp-org：metadata-1-0 / upnp /xmlns：xsi =http://www.w3.org/2001/XMLSchema-instancexsi：schemaLocation =
 urn： schemas-upnp-org：metadata-1-0 / DIDL-Lite / 
 http://www.upnp.org/schema s / av / didl-lite-v2-20060531.xsd 
 urn：schemas-upnp-org：metadata-1-0 / upnp / 
 http://www.upnp.org/schemas/av /upnp-v2-20061231.xsd\"> 
< item id =18parentID =13restricted =0>< / item> 
< / DIDL-Lite> 
  

可以很漂亮地打印以符合上述示例。 xml.MarshallIndent还有点原始。




Here's a sample DIDL-Lite XML document from the UPnP AV ContentDirectory v2 Service Template:

<?xml version="1.0" encoding="UTF-8"?>
<DIDL-Lite
 xmlns:dc="http://purl.org/dc/elements/1.1/"
 xmlns="urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/"
 xmlns:upnp="urn:schemas-upnp-org:metadata-1-0/upnp/"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="
   urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/
    http://www.upnp.org/schemas/av/didl-lite-v2-20060531.xsd
   urn:schemas-upnp-org:metadata-1-0/upnp/
    http://www.upnp.org/schemas/av/upnp-v2-20061231.xsd">
   <item id="18" parentID="13" restricted="0">
      ...
   </item>
</DIDL-Lite>

How would one go about marshalling to this with Go's xml package? More specifically:

1. How are namespace prefixes defined, such as xmlns:dc and xmlns:upnp?
2. How are multiple name spaces configured on an element?
3. How is the namespace set for attributes, such as the xsi prefix on the schemaLocation attribute?

As a base, I have something like this:

type DIDLLite struct {
    XMLName xml.Name `xml:"urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/ DIDL-Lite"`
    // ??? namespace prefixes dc, upnp, xsi
    Objects []Object
}

I've also found this possibly related bug.

解决方案

The example you gave is marshalled. I assume you mean to ask, "how would one define Go data types that marshal with xml.Marshal into this?"

package main

import (
    "encoding/xml"
    "fmt"
)

type DIDLLite struct {
    XMLName xml.Name
    DC      string   `xml:"xmlns:dc,attr"`
    UPNP    string   `xml:"xmlns:upnp,attr"`
    XSI     string   `xml:"xmlns:xsi,attr"`
    XLOC    string   `xml:"xsi:schemaLocation,attr"`
    Objects []Object `xml:"item"`
}

type Object struct {
    ID         string `xml:"id,attr"`
    Parent     string `xml:"parentID,attr"`
    Restricted string `xml:"restricted,attr"`
}

func main() {
    d := DIDLLite{
        XMLName: xml.Name{
            Space: "urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/",
            Local: "DIDL-Lite",
        },
        DC:   "http://purl.org/dc/elements/1.1/",
        UPNP: "urn:schemas-upnp-org:metadata-1-0/upnp/",
        XSI:  "http://www.w3.org/2001/XMLSchema-instance",
        XLOC: `
   urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/
    http://www.upnp.org/schemas/av/didl-lite-v2-20060531.xsd
   urn:schemas-upnp-org:metadata-1-0/upnp/
    http://www.upnp.org/schemas/av/upnp-v2-20061231.xsd`,
        Objects: []Object{{ID: "18", Parent: "13", Restricted: "0"}},
    }
    b, err := xml.MarshalIndent(d, "", "    ")
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(b))
}

Output:

<DIDL-Lite xmlns="urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:upnp="urn:schemas-upnp-org:metadata-1-0/upnp/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="
   urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/
    http://www.upnp.org/schemas/av/didl-lite-v2-20060531.xsd
   urn:schemas-upnp-org:metadata-1-0/upnp/
    http://www.upnp.org/schemas/av/upnp-v2-20061231.xsd">
    <item id="18" parentID="13" restricted="0"></item>
</DIDL-Lite>

which can be pretty printed to match your example above. xml.MarshallIndent is a little primitive yet.

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