serde能否反序列化格式为扁平键值对的XML数据？

解决方案 #

你遇到的这种<key>和值节点交替排列的扁平XML结构，serde-xml-rs没有内置的serde属性可以直接一步映射到你定义的Data结构体，可通过以下两种方式实现需求：

• 方案一：中间层转换（实现成本最低，推荐）
  先解析为你目前已经实现的元组Vec中间结构，再手动映射为目标结构体：

  #[derive(Deserialize)]
  enum Node {
    #[serde(rename = "int")]
    Int(u32),
    #[serde(rename = "string")]
    String(String),
  }
  
  #[derive(Deserialize)]
  struct DataTemp {
    #[serde(rename = "$value")]
    entries: Vec<(String, Node)>,
  }
  
  struct Data {
    version: Node,
    name: Node,
  }
  
  // 解析转换逻辑
  let xml_str = r#"
  <data>
     <key>version</key>
     <int>4</int>
     <key>name</key>
     <string>John</string>
  </data>
  "#;
  let temp: DataTemp = serde_xml_rs::from_str(xml_str)?;
  let mut entries_iter = temp.entries.into_iter();
  let data = Data {
      version: entries_iter.find(|(k, _)| k == "version").unwrap().1,
      name: entries_iter.find(|(k, _)| k == "name").unwrap().1,
  };
  

• 方案二：自定义Data的反序列化逻辑（可直接一步解析）
  为Data手动实现Deserialize trait，主动处理交替的key-value结构：

  use serde::de::{Deserialize, Deserializer, MapAccess, Visitor};
  use std::fmt;
  
  impl<'de> Deserialize<'de> for Data {
      fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
      where
          D: Deserializer<'de>,
      {
          struct DataVisitor;
  
          impl<'de> Visitor<'de> for DataVisitor {
              type Value = Data;
  
              fn expecting(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                  f.write_str("alternating key and value nodes")
              }
  
              fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
              where
                  A: MapAccess<'de>,
              {
                  let mut version = None;
                  let mut name = None;
  
                  while let Some(key) = map.next_key::<String>()? {
                      match key.as_str() {
                          "version" => version = Some(map.next_value()?),
                          "name" => name = Some(map.next_value()?),
                          _ => { let _: Node = map.next_value()?; }
                      }
                  }
  
                  Ok(Data {
                      version: version.ok_or_else(|| serde::de::Error::missing_field("version"))?,
                      name: name.ok_or_else(|| serde::de::Error::missing_field("name"))?,
                  })
              }
          }
  
          deserializer.deserialize_map(DataVisitor)
      }
  }
  
  // 直接解析即可得到Data实例
  let data: Data = serde_xml_rs::from_str(xml_str)?;
  

内容的提问来源于stack exchange，提问作者Vigdail