从Scala中的命令行获取Xpath [英] Get Xpath from command line in scala

问题描述

import scala.io.Source
import scala.xml.{Node, NodeSeq, XML}

object scalaTest extends App {


var test= <name>person
<fname>doe
<first>john</first>
</fname>
</name>


var s=scala.io.StdIn.readLine
var result=s.asInstanceOf[NodeSeq]

println(result)


}

当我提供xpath测试\ fname ＼ p命令行上的 first，它会抛出

When i provide xpath test\"fname"\"first" on command line, it throws,

test\"fname"\"first"
Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to scala.xml.NodeSeq
    at scalaTest$.delayedEndpoint$scalaTest$1(scalaTest.scala:15)
    at scalaTest$delayedInit$body.apply(scalaTest.scala:4)
    at scala.Function0.apply$mcV$sp(Function0.scala:34)
    at scala.Function0.apply$mcV$sp$(Function0.scala:34)
    at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
    at scala.App.$anonfun$main$1$adapted(App.scala:76)
    at scala.collection.immutable.List.foreach(List.scala:389)
    at scala.App.main(App.scala:76)
    at scala.App.main$(App.scala:74)
    at scalaTest$.main(scalaTest.scala:4)
    at scalaTest.main(scalaTest.scala)

如何提供xpath在命令行中以test\ fname \ first的形式获取结果，

How to provide xpath as test\"fname"\"first" in command line and get result as,

<first>john</first>

推荐答案

您不能只是 cast String 到 NodeSeq 中。您可以尝试使用 XML.loadString（...） 解析。但这也不是您想要的，因为您的字符串不包含xml，它包含一些类似于xpath的选择。我不知道Scala的内置XML是否实际上支持Xpath。我只知道它在 NodeSeq 上有一些有趣的方法，例如 \ 和 ＼ em 看起来有点像Xpath 。您可以做的是：

You cannot just cast a String into a NodeSeq. You could attempt to parse it with XML.loadString(...). But this is also not what you want, because your string does not contain xml, it contains some xpath-like selection. I don't know whether Scala's built-in XML actually supports Xpath. I only know that it has a few funny methods on NodeSeqs like \ and \\ that look somewhat like Xpath. What you could do is:

• 从stdin中获取输入字符串


• 在'\'-字符


• foldLeft \ 方法

• get input string from stdin
• split your input string at the '\'-character
• foldLeft the test-xml node using the \-method

类似的东西可以工作：

import scala.xml.NodeSeq
val test = <name>person<fname>doe<first>john</first></fname></name>
val xpath = """fname\first""" // or read from StdIn
val selectedElement = xpath.split("\\\\").foldLeft[NodeSeq](test){
  case (elem, tagName) => elem \ tagName 
}

// gives result:
// res20: scala.xml.NodeSeq = NodeSeq(<first>john</first>)

或更短：

val selectedElement = xpath.split("\\\\").foldLeft[NodeSeq](test)(_ \ _)

另一注：您当然不能在StdIn输入中使用字符串 test 。编译器应该如何知道它与本地 test 变量有什么关系？

Another note: you of course cannot use the String "test" in your StdIn input. How is the compiler supposed to know that it has anything to do with the local test-variable?

这篇关于从Scala中的命令行获取Xpath的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！