Kotlin - 使用simpleXML解析xml内联列表

Question

我正在尝试使用kotlin中的simplexml解析rss feed.

该Feed是来自itunes的顶级播客

返回的数据具有以下结构:

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
  <channel>
    <title>Top Audio Podcasts</title>
    <link>https://rss.itunes.apple.com/api/v1/us/podcasts/top-podcasts/all/10/explicit.rss</link>
    <lastBuildDate>Fri, 13 Jul 2018 01:36:19 -0700</lastBuildDate>
    <atom:link rel="self" type="application/rss+xml" href="https://rss.itunes.apple.com/api/v1/us/podcasts/top-podcasts/all/10/explicit.rss"/>
    <atom:link rel="alternate" type="text/html" href="https://itunes.apple.com/WebObjects/MZStore.woa/wa/viewTop?genreId=26&amp;popId=28"/>
    <description>iTunes Store : Top Audio Podcasts</description>
    <category>iTunes Store</category>
    <copyright>Copyright © 2018 Apple Inc. All rights reserved.</copyright>
    <item>
      <title>The Wilderness - Crooked Media</title>
      <category domain="">Crooked Media</category>
      <link>https://itunes.apple.com/us/podcast/the-wilderness/id1408796715?mt=2</link>
      <guid>https://itunes.apple.com/us/podcast/the-wilderness/id1408796715?mt=2</guid>
      <description>The Wilderness</description>
      <category>podcast</category>
      <category>News &amp; Politics</category>
      <category>Podcasts</category>
      <category>Society &amp; Culture</category>
      <category>History</category>
      <pubDate>Fri, 6 Jul 2018 00:00:00 +0000</pubDate>
    </item>
    <item>
      <title>Aaron Mahnke's Cabinet of Curiosities - HowStuffWorks &amp; Aaron Mahnke</title>
      <category domain="https://itunes.apple.com/us/artist/howstuffworks-aaron-mahnke/284341002?mt=2">HowStuffWorks &amp; Aaron Mahnke</category>
      <link>https://itunes.apple.com/us/podcast/aaron-mahnkes-cabinet-of-curiosities/id1396546917?mt=2</link>
      <guid>https://itunes.apple.com/us/podcast/aaron-mahnkes-cabinet-of-curiosities/id1396546917?mt=2</guid>
      <description>Aaron Mahnke's Cabinet of Curiosities</description>
      <category>podcast</category>
      <category>History</category>
      <category>Podcasts</category>
      <category>Society &amp; Culture</category>
      <pubDate>Tue, 10 Jul 2018 00:00:00 +0000</pubDate>
    </item>
  </channel>
</rss>

我关心的部分是项目标签包含的播客列表.

模型类我看起来像这样:

@Root(name = "channel", strict = false)
data class Chart @JvmOverloads constructor(
        @field:ElementList(entry = "item", inline = true)
        @param:ElementList(entry = "item", inline = true)
        val podcasts: List<Entry>? = null)

@Root(name = "item", strict = false)
data class Entry @JvmOverloads constructor(
        @field:Element(name = "description")
        @param:Element(name = "description")
        val title: String? = null,

        @field:Element(name = "category")
        @param:Element(name = "category")
        val artist: String? = null,

        @field:Element(name = "guid")
        @param:Element(name = "guid")
        val guid: String? = null)

我有一个简单的单元测试,从文件加载xml,将其传递给simplexml反序列化器,然后将输出与一些预期的模型进行比较.

在我运行测试的那一刻,我得到一个例外:

org.simpleframework.xml.core.ValueRequiredException: Unable to satisfy @org.simpleframework.xml.ElementList(entry=item, inline=true, data=false, name=, type=void, required=true, empty=true) on field 'podcasts' private final java.util.List Chart.podcasts for class Chart at line 2

向@ElementList注释添加required = false会删除此错误,但反序列化器会为列表返回null.

我最好的猜测是反序列化器无法找到项目列表,尽管根据我对@ElementList的理解,使用输入字段应该允许它找到标签.

此代码的用例是形成Android应用程序的网络层,该应用程序依赖于Retrofit2进行REST调用.

感谢您提供的任何帮助.

注意:使用@Param和@Field声明是为了解决另一个异常,我从这个问题中得到了一个想法

Answer 1

我找到了解决方案.

所以第一个问题是我的根元素不是Chart,因为它代表了channel标签,我需要一个包装类,我称之为ChartFeed来表示rss标签.

我通过在Chart对象上添加title标签的元素来实现这一点,这也是不可行的.

我完成的数据类如下所示:

@Root(name = "rss", strict = false)
data class ChartFeed(
        @field:Element(name = "channel")
        @param:Element(name = "channel")
        val chart: Chart? = null)

@Root(name = "channel", strict = false)
data class Chart @JvmOverloads constructor(
        @field:ElementList(entry = "item", inline = true)
        @param:ElementList(entry = "item", inline = true)
        val podcasts: List<Entry>? = null)

@Root(name = "item", strict = false)
data class Entry @JvmOverloads constructor(
        @field:Path("description")
        @field:Text(required = false)
        @param:Path("description")
        @param:Text(required = false)
        val title: String? = null,

        @field:Path("category")
        @field:Text(required = false)
        @param:Path("category")
        @param:Text(required = false)
        val artist: String? = null,

        @field:Element(name = "guid")
        @param:Element(name = "guid")
        val guid: String? = null)

我已经将@Element标记的几个字段/参数更改为@Path和@Text的组合,这是因为channel和item xml对象都重用了导致此异常的相同标记:

org.simpleframework.xml.core.PersistenceException: Element 'category' is already used with @org.simpleframework.xml.Element(name=category, type=void, data=false, required=true) on field 'artist' private final java.lang.String Entry.artist at line 18

我使用的解决方案在此处详述