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Scala で XML を整形する

Scala

人間が読める状態でない XML を整形したいとき、整形してくれる Web サービスはたくさんあるものの、仕事で扱ってるデータなどであれば、そういうところに食わせるわけにはいきません。

こういうとき Scalascala.xml.PrettyPrinter でさくっと整形するのが便利です。

http://www.scala-lang.org/api/current/index.html#scala.xml.PrettyPrinter

例えば、こんな XML があったとして

<?xml version="1.0"?><catalog><book id="bk101"><author>Gambardella, Matthew</author><title>XML Developer's Guide</title><genre>Computer</genre><price>44.95</price><publish_date>2000-10-01</publish_date><description>An in-depth look at creating applications 
      with XML.</description></book><book id="bk102"><author>Ralls, Kim</author><title>Midnight Rain</title><genre>Fantasy</genre><price>5.95</price><publish_date>2000-12-16</publish_date><description>A former architect battles corporate zombies, 
      an evil sorceress, and her own childhood to become queen 
      of the world.</description></book><book id="bk103"><author>Corets, Eva</author><title>Maeve Ascendant</title><genre>Fantasy</genre><price>5.95</price><publish_date>2000-11-17</publish_date><description>After the collapse of a nanotechnology 
      society in England, the young survivors lay the 
      foundation for a new society.</description></book><book id="bk104"><author>Corets, Eva</author><title>Oberon's Legacy</title><genre>Fantasy</genre><price>5.95</price><publish_date>2001-03-10</publish_date><description>In post-apocalypse England, the mysterious 
      agent known only as Oberon helps to create a new life 
      for the inhabitants of London. Sequel to Maeve 
      Ascendant.</description></book><book id="bk105"><author>Corets, Eva</author><title>The Sundered Grail</title><genre>Fantasy</genre><price>5.95</price><publish_date>2001-09-10</publish_date><description>The two daughters of Maeve, half-sisters, 
      battle one another for control of England. Sequel to 
      Oberon's Legacy.</description></book><book id="bk106"><author>Randall, Cynthia</author><title>Lover Birds</title><genre>Romance</genre><price>4.95</price><publish_date>2000-09-02</publish_date><description>When Carla meets Paul at an ornithology 
      conference, tempers fly as feathers get ruffled.</description></book><book id="bk107"><author>Thurman, Paula</author><title>Splish Splash</title><genre>Romance</genre><price>4.95</price><publish_date>2000-11-02</publish_date><description>A deep sea diver finds true love twenty 
      thousand leagues beneath the sea.</description></book><book id="bk108"><author>Knorr, Stefan</author><title>Creepy Crawlies</title><genre>Horror</genre><price>4.95</price><publish_date>2000-12-06</publish_date><description>An anthology of horror stories about roaches,
      centipedes, scorpions  and other insects.</description></book><book id="bk109"><author>Kress, Peter</author><title>Paradox Lost</title><genre>Science Fiction</genre><price>6.95</price><publish_date>2000-11-02</publish_date><description>After an inadvertant trip through a Heisenberg
      Uncertainty Device, James Salway discovers the problems 
      of being quantum.</description></book><book id="bk110"><author>O'Brien, Tim</author><title>Microsoft .NET: The Programming Bible</title><genre>Computer</genre><price>36.95</price><publish_date>2000-12-09</publish_date><description>Microsoft's .NET initiative is explored in 
      detail in this deep programmer's reference.</description></book><book id="bk111"><author>O'Brien, Tim</author><title>MSXML3: A Comprehensive Guide</title><genre>Computer</genre><price>36.95</price><publish_date>2000-12-01</publish_date><description>The Microsoft MSXML3 parser is covered in 
      detail, with attention to XML DOM interfaces, XSLT processing, 
      SAX and more.</description></book><book id="bk112"><author>Galos, Mike</author><title>Visual Studio 7: A Comprehensive Guide</title><genre>Computer</genre><price>49.95</price><publish_date>2001-04-16</publish_date><description>Microsoft Visual Studio 7 is explored in depth,
      looking at how Visual Basic, Visual C++, C#, and ASP+ are 
      integrated into a comprehensive development 
      environment.</description></book></catalog>

これを「input.xml」というファイル名で保存しておいて scala コマンドか sbt console で REPL を起動して以下のように実行します。

import scala.xml._

val xml: Elem = XML.load("input.xml")
val formatted: String = new PrettyPrinter(80, 2).format(xml)

println(formatted)

すると、以下のように整形された XML を取得できます。

<catalog>
  <book id="bk101">
    <author>Gambardella, Matthew</author>
    <title>XML Developer's Guide</title>
    <genre>Computer</genre>
    <price>44.95</price>
    <publish_date>2000-10-01</publish_date>
    <description>An in-depth look at creating applications with XML.</description>
  </book>
  <book id="bk102">
    <author>Ralls, Kim</author>
    <title>Midnight Rain</title>
    <genre>Fantasy</genre>
    <price>5.95</price>
    <publish_date>2000-12-16</publish_date>
    <description>
      A former architect battles corporate zombies, 
      an evil sorceress, and her own childhood to become queen 
      of the world.
    </description>
  </book>
  <book id="bk103">
    <author>Corets, Eva</author>
    <title>Maeve Ascendant</title>
    <genre>Fantasy</genre>
    <price>5.95</price>
    <publish_date>2000-11-17</publish_date>
    <description>
      After the collapse of a nanotechnology 
      society in England, the young survivors lay the 
      foundation for a new society.
    </description>
  </book>
  <book id="bk104">
    <author>Corets, Eva</author>
    <title>Oberon's Legacy</title>
    <genre>Fantasy</genre>
    <price>5.95</price>
    <publish_date>2001-03-10</publish_date>
    <description>
      In post-apocalypse England, the mysterious 
      agent known only as Oberon helps to create a new life 
      for the inhabitants of London. Sequel to Maeve 
      Ascendant.
    </description>
  </book>
  <book id="bk105">
    <author>Corets, Eva</author>
    <title>The Sundered Grail</title>
    <genre>Fantasy</genre>
    <price>5.95</price>
    <publish_date>2001-09-10</publish_date>
    <description>
      The two daughters of Maeve, half-sisters, 
      battle one another for control of England. Sequel to 
      Oberon's Legacy.
    </description>
  </book>
  <book id="bk106">
    <author>Randall, Cynthia</author>
    <title>Lover Birds</title>
    <genre>Romance</genre>
    <price>4.95</price>
    <publish_date>2000-09-02</publish_date>
    <description>
      When Carla meets Paul at an ornithology 
      conference, tempers fly as feathers get ruffled.
    </description>
  </book>
  <book id="bk107">
    <author>Thurman, Paula</author>
    <title>Splish Splash</title>
    <genre>Romance</genre>
    <price>4.95</price>
    <publish_date>2000-11-02</publish_date>
    <description>
      A deep sea diver finds true love twenty 
      thousand leagues beneath the sea.
    </description>
  </book>
  <book id="bk108">
    <author>Knorr, Stefan</author>
    <title>Creepy Crawlies</title>
    <genre>Horror</genre>
    <price>4.95</price>
    <publish_date>2000-12-06</publish_date>
    <description>
      An anthology of horror stories about roaches,
      centipedes, scorpions  and other insects.
    </description>
  </book>
  <book id="bk109">
    <author>Kress, Peter</author>
    <title>Paradox Lost</title>
    <genre>Science Fiction</genre>
    <price>6.95</price>
    <publish_date>2000-11-02</publish_date>
    <description>
      After an inadvertant trip through a Heisenberg
      Uncertainty Device, James Salway discovers the problems 
      of being quantum.
    </description>
  </book>
  <book id="bk110">
    <author>O'Brien, Tim</author>
    <title>Microsoft .NET: The Programming Bible</title>
    <genre>Computer</genre>
    <price>36.95</price>
    <publish_date>2000-12-09</publish_date>
    <description>
      Microsoft's .NET initiative is explored in 
      detail in this deep programmer's reference.
    </description>
  </book>
  <book id="bk111">
    <author>O'Brien, Tim</author>
    <title>MSXML3: A Comprehensive Guide</title>
    <genre>Computer</genre>
    <price>36.95</price>
    <publish_date>2000-12-01</publish_date>
    <description>
      The Microsoft MSXML3 parser is covered in 
      detail, with attention to XML DOM interfaces, XSLT processing, 
      SAX and more.
    </description>
  </book>
  <book id="bk112">
    <author>Galos, Mike</author>
    <title>Visual Studio 7: A Comprehensive Guide</title>
    <genre>Computer</genre>
    <price>49.95</price>
    <publish_date>2001-04-16</publish_date>
    <description>
      Microsoft Visual Studio 7 is explored in depth,
      looking at how Visual Basic, Visual C++, C#, and ASP+ are 
      integrated into a comprehensive development 
      environment.
    </description>
  </book>
</catalog>

XML をファイルに保存するのがまどろっこしければ、ヒアドキュメントで以下のようにします。

import scala.xml._

val input = """XML の中身"""
val xml: Elem = XML.loadString(input)