XMLStream Reader Scala-END_DOCUMENT的正确处理

问题描述

我实际上是在重组现有的大型软件，并从XMLEventReader切换到 XMLStreamReader用于提高内存效率。

考虑以下函数的定义，该函数当前仅读取XML事件并打印它们：

def evalStreamReader(source: StreamSource): Unit

    val StreamReader = XMLInputFactory.newInstance().createXMLStreamReader(source)
    while (StreamReader.hasNext) {
      val eventType = StreamReader.getEventType
      eventType match {
        case 1 => println("Start Element " + eventType + " : " + StreamReader.getLocalName)
        case 2 => println("End Element " + eventType + " : " + StreamReader.getLocalName)
        case 4 => println("Characters " + eventType + " : " + StreamReader.getText)
        case 7 => println("Start Document " + eventType)
        case 8 => println("End Document: " + eventType)

      }
      StreamReader.next()
    }
}

和简单的XML文件：

<a>
  <c></c>
</a>

输出为：

Start Document 7
Start Element 1 : a
Characters 4 : 
  
Start Element 1 : c
End Element 2 : c
Characters 4 : 

End Element 2 : a

无论如何，我是否可以在END_DOCUMENT条件/大小写匹配内而不是在循环之外单独/正确地处理事件While？我尝试了许多条件，但do while却没有成功。

想法是StreamReader.next()将在END_DOCUMENT事件中切换光标，而hasNext将根据API中的定义返回false：

boolean hasNext()
         throws XMLStreamException
Returns true if there are more parsing events and false if there are no more events. 
This method will return false if the current state of the XMLStreamReader is END_DOCUMENT

解决方法

一种简单的非惯用方法：

def evalStreamReader(source: StreamSource): Unit = {
  val streamReader: XMLStreamReader = XMLInputFactory.newInstance().createXMLStreamReader(source)
  var finished: Boolean = false

  do {
    val eventType = streamReader.getEventType

    if (eventType != 8) {
      eventType match {
        case 1 => println("Start Element " + eventType + " : " + streamReader.getLocalName)
        case 2 => println("End Element " + eventType + " : " + streamReader.getLocalName)
        case 4 => println("Characters " + eventType + " : " + streamReader.getText)
        case 7 => println("Start Document " + eventType)
      }
      streamReader.next()
    } else {
      println("End Document: " + eventType)
      finished = true
    }
  } while(!finished)
  streamReader.close()
}

它将输出：

Start Document 7
Start Element 1 : a
Characters 4 : 
  
Start Element 1 : c
End Element 2 : c
Characters 4 : 

End Element 2 : a
End Document: 8

基本上，您需要将流控制与阅读器分开。