将带有嵌套标签的 XML 读入 Spark RDD，并转换为 JSON

Posted 2023-03-31

【中文标题】将带有嵌套标签的 XML 读入 Spark RDD，并转换为 JSON

【英文标题】：Reading XML with nested tags into a Spark RDD, and transforming to JSON

【发布时间】：2017-08-12 20:27:25

【问题描述】：

我有以下 xml 结构：

<root>
  <items>
    <item>
      <property>1</property>
      <property2>2</property2> 
      <nested-property>
        <property>1</property>
      </nested-property>   
    </item>
  </items>
</root>

我在其 Scala API 中使用 Spark 2.2，并且在本地文件系统 (10GB) 中有相当大的 XML 文件。

我的目标是读取每个元素，进行一些转换并将其转换为 Json，但结果应该与我提供的 XML 相似。

关键是我需要迭代文件不是逐行，而是“逐个标签”，在这种情况下，从标签到下一个

还有一点是我需要读取嵌套的 xml 标签，所以我不确定this library 是否可以帮助我。我的理解是 不读取 XML 嵌套标签，而且它只是在使用 DataFrames，我也更喜欢 RDD。有没有办法实现 功能？

我尝试只读取文本文件并使用标记项作为分隔符，但它不起作用。它仍然将换行符视为分隔符：

  val spark = SparkSession
    .builder()
    .config("textinputformat.record.delimiter", "</item>")
    .master("local[*]")
    .getOrCreate()


  val documents = spark.sparkContext.textFile("/home/myuser/test-data/Records.xml")

如何处理嵌套的 XML 元素？我将如何访问它们？

我不想展平嵌套结构， 我想将我遍历的每个 XML 行转换为一个单独的 JSON 文件 - 具有相同的结构。

【问题讨论】：

你试过这个库吗？ github.com/databricks/spark-xml/blob/master/README.md

请检查我的答案！也可以访问这个test case，你也可以无缝地将数据帧转换为rdd（使用.rdd毫不费力）

嗨@RamGhadiyaram - 您的回答可能对其他人有用，也许您可​​以再次添加。谢谢。

@Filipe Miranda 添加了回来。

【参考方案1】：

问题：如何处理嵌套的 XML 元素？我将如何访问 他们？

对于展平嵌套结构，您可以使用explode...

示例：假设我想要每个标题（字符串类型）/作者（WrappedArray）组合，可以使用explode 实现它：

架构： 根 |-- 标题：字符串（可为空=真） |-- 作者：数组（可为空=真） | |-- 元素：结构（containsNull = true） | | |-- 初始：数组（可为空=真） | | | |-- 元素：字符串（包含Null = true） | | |-- 姓氏：字符串（可为空=真） 显示（） +--------------------------------+--------+ |标题|作者| +--------------------------------+--------+ |...的正确运动|[[WrappedArray(J,...| |2055年目录...|[[WrappedArray(J,...| |空|空| |目录 von 3356 ...|[[WrappedArray(J)...| |星象目录...|[[WrappedArray(P)...| |星象目录...|[[WrappedArray(P)...| |观察结果...|[[WrappedArray(H,...| | AGK3 目录|[[WrappedArray(W)...| |珀斯 70：一个 Catal...|[[WrappedArray(E)...| 导入 org.apache.spark.sql.functions； DataFrame exploded = src.select(src.col("title"),functions.explode(src.col("author")).as("auth")) .select("title","auth.initial","auth.lastName"); 爆炸=exploded.select（exploded.col（“初始”）， exploded.col("title").as("title"), exploded.col("lastName")); 爆炸的.printSchema 爆炸的.show 根 |-- 初始：数组（可为空=真） | |-- 元素：字符串（包含Null = true） |-- 标题：字符串（可为空=真） |-- 姓氏：字符串（可为空=真） +-------+--------+-------------+ |初始|标题|姓氏| +-------+--------+-------------+ | [J, H]|...的适当运动|斯宾塞| | [J]|...的适当运动|杰克逊| | [J, H]|2055年目录...|斯宾塞|

示例 xml 文件

<?xml version='1.0' ?>
<!DOCTYPE datasets SYSTEM "http://www.cs.washington.edu/research/projects/xmltk/xmldata/data/nasa/dataset_053.dtd">
<datasets>
 <dataset subject="astronomy" xmlns:xlink="http://www.w3.org/XML/XLink/0.9">
  <title>Proper Motions of Stars in the Zone Catalogue -40 to -52 degrees
of 20843 Stars for 1900</title>
  <altname type="ADC">1005</altname>
  <altname type="CDS">I/5</altname>
  <altname type="brief">Proper Motions in Cape Zone Catalogue -40/-52</altname>
  <reference>
   <source>
    <other>
     <title>Proper Motions of Stars in the Zone Catalogue -40 to -52 degrees
of 20843 Stars for 1900</title>
     <author>
      <initial>J</initial>
      <initial>H</initial>
      <lastName>Spencer</lastName>
     </author>
     <author>
      <initial>J</initial>
      <lastName>Jackson</lastName>
     </author>
     <name>His Majesty's Stationery Office, London</name>
     <publisher>???</publisher>
     <city>???</city>
     <date>
      <year>1936</year>
     </date>
    </other>
   </source>
  </reference>
  <keywords parentListURL="http://messier.gsfc.nasa.gov/xml/keywordlists/adc_keywords.html">
   <keyword xlink:href="Positional_data.html">Positional data</keyword>
   <keyword xlink:href="Proper_motions.html">Proper motions</keyword>
  </keywords>
  <descriptions>
   <description>
    <para>This catalog, listing the proper motions of 20,843 stars
    from the Cape Astrographic Zones, was compiled from three series of
    photographic plates. The plates were taken at the Royal Observatory,
    Cape of Good Hope, in the following years: 1892-1896, 1897-1910,
    1923-1928. Data given include centennial proper motion, photographic
    and visual magnitude, Harvard spectral type, Cape Photographic
    Durchmusterung (CPD) identification, epoch, right ascension and
    declination for 1900.</para>
   </description>
   <details/>
  </descriptions>
  <tableHead>
   <tableLinks>
    <tableLink xlink:href="czc.dat">
     <title>The catalogue</title>
    </tableLink>
   </tableLinks>
   <fields>
    <field>
     <name>---</name>
     <definition>Number 5</definition>
     <units>---</units>
    </field>
    <field>
     <name>CZC</name>
     <definition>Catalogue Identification Number</definition>
     <units>---</units>
    </field>
    <field>
     <name>Vmag</name>
     <definition>Visual Magnitude</definition>
     <units>mag</units>
    </field>
    <field>
     <name>RAh</name>
     <definition>Right Ascension for 1900 hours</definition>
     <units>h</units>
    </field>
    <field>
     <name>RAm</name>
     <definition>Right Ascension for 1900 minutes</definition>
     <units>min</units>
    </field>
    <field>
     <name>RAcs</name>
     <definition>Right Ascension seconds in 0.01sec 1900</definition>
     <units>0.01s</units>
    </field>
    <field>
     <name>DE-</name>
     <definition>Declination Sign</definition>
     <units>---</units>
    </field>
    <field>
     <name>DEd</name>
     <definition>Declination for 1900 degrees</definition>
     <units>deg</units>
    </field>
    <field>
     <name>DEm</name>
     <definition>Declination for 1900 arcminutes</definition>
     <units>arcmin</units>
    </field>
    <field>
     <name>DEds</name>
     <definition>Declination for 1900 arcseconds</definition>
     <units>0.1arcsec</units>
    </field>
    <field>
     <name>Ep-1900</name>
     <definition>Epoch -1900</definition>
     <units>cyr</units>
    </field>
    <field>
     <name>CPDZone</name>
     <definition>Cape Photographic
                                        Durchmusterung Zone</definition>
     <units>---</units>
    </field>
    <field>
     <name>CPDNo</name>
     <definition>Cape Photographic Durchmusterung Number</definition>
     <units>---</units>
    </field>
    <field>
     <name>Pmag</name>
     <definition>Photographic Magnitude</definition>
     <units>mag</units>
    </field>
    <field>
     <name>Sp</name>
     <definition>HD Spectral Type</definition>
     <units>---</units>
    </field>
    <field>
     <name>pmRAs</name>
     <definition>Proper Motion in RA
      <footnote>
       <para>the relation is   pmRA = 15 * pmRAs * cos(DE)
    if pmRAs is expressed in s/yr and pmRA in arcsec/yr</para>
      </footnote>
     </definition>
     <units>0.1ms/yr</units>
    </field>
    <field>
     <name>pmRA</name>
     <definition>Proper Motion in RA</definition>
     <units>mas/yr</units>
    </field>
    <field>
     <name>pmDE</name>
     <definition>Proper Motion in Dec</definition>
     <units>mas/yr</units>
    </field>
   </fields>
  </tableHead>
  <history>
   <ingest>
    <creator>
     <lastName>Julie Anne Watko</lastName>
     <affiliation>SSDOO/ADC</affiliation>
    </creator>
    <date>
     <year>1995</year>
     <month>Nov</month>
     <day>03</day>
    </date>
   </ingest>
  </history>
  <identifier>I_5.xml</identifier>
 </dataset>
 <dataset subject="astronomy" xmlns:xlink="http://www.w3.org/XML/XLink/0.9">
  <title>Catalogue of 20554 Faint Stars in the Cape Astrographic Zone -40 to -52 Degrees
for the Equinox of 1900.0</title>
  <altname type="ADC">1006</altname>
  <altname type="CDS">I/6</altname>
  <altname type="brief">Cape 20554 Faint Stars, -40 to -52, 1900.0</altname>
  <reference>
   <source>
    <other>
     <title>Catalogue of 20554 Faint Stars in the Cape Astrographic Zone -40 to -52 Degrees
for the Equinox of 1900.0</title>
     <author>
      <initial>J</initial>
      <initial>H</initial>
      <lastName>Spencer</lastName>
     </author>
     <author>
      <initial>J</initial>
      <lastName>Jackson</lastName>
     </author>
     <name>His Majesty's Stationery Office, London</name>
     <publisher>???</publisher>
     <city>???</city>
     <date>
      <year>1939</year>
     </date>
     <bibcode>1939HMSO..C......0S</bibcode>
    </other>
   </source>
  </reference>
  <keywords parentListURL="http://messier.gsfc.nasa.gov/xml/keywordlists/adc_keywords.html">
   <keyword xlink:href="Positional_data.html">Positional data</keyword>
   <keyword xlink:href="Proper_motions.html">Proper motions</keyword>
  </keywords>
  <descriptions>
   <description>
    <para>This catalog contains positions, precessions, proper motions, and
  photographic magnitudes for 20,554 stars.  These were derived from
  photographs taken at the Royal Observatory, Cape of Good Hope between 1923
  and 1928.  It covers the astrographic zones -40 degrees to -52 degrees of
  declination.  The positions are given for epoch 1900 (1900.0).  It includes
  spectral types for many of the stars listed.  It extends the earlier
  catalogs derived from the same plates to fainter magnitudes.  The
  computer-readable version consists of a single data table.</para>
    <para>The stated probable error for the star positions is 0.024 seconds of time
  (R.A.) and 0.25 seconds of arc (dec.) for stars with one determination,
  0.017 seconds of time, and 0.18 seconds of arc for two determinations, and
  0.014 / 0.15 for stars with three determinations.</para>
    <para>The precession and secular variations were derived from Newcomb's constants.</para>
    <para>The authors quote probable errors of the proper motions in both coordinates
  of 0.008 seconds of arc for stars with one determination, 0.0055 seconds for
  stars with two determinations, and 0.0044 for stars with three.</para>
    <para>The photographic magnitudes were derived from the measured diameters on the
  photographic plates and from the magnitudes given in the Cape Photographic
  Durchmusterung.</para>
    <para>The spectral classification of the cataloged stars was done with the
  assistance of Annie Jump Cannon of the Harvard College Observatory.</para>
    <para>The user should consult the source reference for more details of the
  measurements and reductions.  See also the notes in this document for
  additional information on the interpretation of the entries.</para>
   </description>
   <details/>
  </descriptions>
  <tableHead>
   <tableLinks>
    <tableLink xlink:href="faint.dat">
     <title>Data</title>
    </tableLink>
   </tableLinks>
   <fields>
    <field>
     <name>ID</name>
     <definition>Cape Number</definition>
     <units>---</units>
    </field>
    <field>
     <name>rem</name>
     <definition>Remark
      <footnote>
       <para>A = Astrographic Star
   F = Faint Proper Motion Star
   N = Other Note</para>
      </footnote>
     </definition>
     <units>---</units>
    </field>
    <field>
     <name>CPDZone</name>
     <definition>Cape Phot. Durchmusterung (CPD) Zone
      <footnote>
       <para>All CPD Zones are negative. - signs are not included in data.
        "0" in column 8 signifies Astrographic Plate instead of CPD.</para>
      </footnote>
     </definition>
     <units>---</units>
    </field>
    <field>
     <name>CPD</name>
     <definition>CPD Number or Astrographic Plate
      <footnote>
       <para>See also note on CPDZone.
        Astrographic plate listed "is the more southerly on which the
        star occurs." Thus, y-coordinate is positive wherever possible.</para>
      </footnote>
     </definition>
     <units>---</units>
    </field>
    <field>
     <name>n_CPD</name>
     <definition>[1234] Remarks
      <footnote>
       <para>A number from 1-4 appears in this byte for double stars where
    the same CPD number applies to more than one star.</para>
      </footnote>
     </definition>
     <units>---</units>
    </field>
    <field>
     <name>mpg</name>
     <definition>Photographic Magnitude
      <footnote>
       <para>The Photographic Magnitude is "determined from the CPD Magnitude
        and the diameter on the Cape Astrographic Plates by means of the
        data given in the volume on the Magnitudes of Stars in the Cape
        Zone Catalogue."
    A null value (99.9) signifies a variable star.</para>
      </footnote>
     </definition>
     <units>mag</units>
    </field>
    <field>
     <name>RAh</name>
     <definition>Mean Right Ascension hours 1900</definition>
     <units>h</units>
    </field>
    <field>
     <name>RAm</name>
     <definition>Mean Right Ascension minutes 1900</definition>
     <units>min</units>
    </field>
    <field>
     <name>RAs</name>
     <definition>Mean Right Ascension seconds 1900</definition>
     <units>s</units>
    </field>
    <field>
     <name>DEd</name>
     <definition>Mean Declination degrees 1900</definition>
     <units>deg</units>
    </field>
    <field>
     <name>DEm</name>
     <definition>Mean Declination arcminutes 1900</definition>
     <units>arcmin</units>
    </field>
    <field>
     <name>DEs</name>
     <definition>Mean Declination arcseconds 1900</definition>
     <units>arcsec</units>
    </field>
    <field>
     <name>N</name>
     <definition>Number of Observations</definition>
     <units>---</units>
    </field>
    <field>
     <name>Epoch</name>
     <definition>Epoch +1900</definition>
     <units>yr</units>
    </field>
    <field>
     <name>pmRA</name>
     <definition>Proper Motion in RA seconds of time</definition>
     <units>s/a</units>
    </field>
    <field>
     <name>pmRAas</name>
     <definition>Proper Motion in RA arcseconds</definition>
     <units>arcsec/a</units>
    </field>
    <field>
     <name>pmDE</name>
     <definition>Proper Motion in Dec arcseconds</definition>
     <units>arcsec/a</units>
    </field>
    <field>
     <name>Sp</name>
     <definition>HD Spectral Type</definition>
     <units>---</units>
    </field>
   </fields>
  </tableHead>
  <history>
   <ingest>
    <creator>
     <lastName>Julie Anne Watko</lastName>
     <affiliation>SSDOO/ADC</affiliation>
    </creator>
    <date>
     <year>1996</year>
     <month>Mar</month>
     <day>26</day>
    </date>
   </ingest>
  </history>
  <identifier>I_6.xml</identifier>
 </dataset>
 <dataset subject="astronomy" xmlns:xlink="http://www.w3.org/XML/XLink/0.9">
  <title>Proper Motions of 1160 Late-Type Stars</title>
  <altname type="ADC">1014</altname>
  <altname type="CDS">I/14</altname>
  <altname type="brief">Proper Motions of 1160 Late-Type Stars</altname>
  <reference>
   <source>
    <journal>
     <title>Proper Motions of 1160 Late-Type Stars</title>
     <author>
      <initial>H</initial>
      <initial>J</initial>
      <lastName>Fogh Olsen</lastName>
     </author>
     <name>Astron. Astrophys. Suppl. Ser.</name>
     <volume>2</volume>
     <pageno>69</pageno>
     <date>
      <year>1970</year>
     </date>
     <bibcode>1970A&amp;AS....2...69O</bibcode>
    </journal>
   </source>
   <related>
    <holding role="similar">II/38 : Stars observed photoelectrically by Dickow et al.
     <xlink:simple href="II/38"/>
    </holding>Fogh Olsen H.J. 1970, Astron. Astrophys. Suppl. Ser., 2, 69.
   Fogh Olsen H.J. 1970, Astron. Astrophys., Suppl. Ser., 1, 189.</related>
  </reference>
  <keywords parentListURL="http://messier.gsfc.nasa.gov/xml/keywordlists/adc_keywords.html">
   <keyword xlink:href="Proper_motions.html">Proper motions</keyword>
  </keywords>
  <descriptions>
   <description>
    <para>Improved proper motions for the 1160 stars contained in the photometric
   catalog by Dickow et al. (1970) are presented. Most of the proper motions
   are from the GC, transferred to the system of FK4. For stars not included
   in the GC, preliminary AGK or SAO proper motions are given. Fogh Olsen
   (Astron. Astrophys. Suppl. Ser., 1, 189, 1970) describes the method of
   improvement. The mean errors of the centennial proper motions increase with
   increasing magnitude. In Right Ascension, these range from 0.0043/cos(dec)
   for very bright stars to 0.096/cos(dec) for the faintest stars. In Dec-
   lination, the range is from 0.065 to 1.14.</para>
   </description>
   <details/>
  </descriptions>
  <tableHead>
   <tableLinks>
    <tableLink xlink:href="pmlate.dat">
     <title>Proper motion data</title>
    </tableLink>
   </tableLinks>
   <fields>
    <field>
     <name>No</name>
     <definition>Number
      <footnote>
       <para>Henry Draper or Bonner Durchmusterung number</para>
      </footnote>
     </definition>
     <units>---</units>
    </field>
    <field>
     <name>pmRA</name>
     <definition>Centennial Proper Motion RA</definition>
     <units>s/ca</units>
    </field>
    <field>
     <name>pmDE</name>
     <definition>Centennial Proper Motion Dec</definition>
     <units>arcsec/ca</units>
    </field>
    <field>
     <name>RV</name>
     <definition>Radial Velocity</definition>
     <units>km/s</units>
    </field>
   </fields>
  </tableHead>
  <history>
   <ingest>
    <creator>
     <lastName>Julie Anne Watko</lastName>
     <affiliation>ADC</affiliation>
    </creator>
    <date>
     <year>1996</year>
     <month>Jun</month>
     <day>03</day>
    </date>
   </ingest>
  </history>
  <identifier>I_14.xml</identifier>
 </dataset>
 <dataset subject="astronomy" xmlns:xlink="http://www.w3.org/XML/XLink/0.9">
  <title>Katalog von 3356 Schwachen Sternen fuer das Aequinoktium 1950
+89 degrees</title>
  <altname type="ADC">1016</altname>
  <altname type="CDS">I/16</altname>
  <altname type="brief">Catalog of 3356 Faint Stars, 1950</altname>
  <reference>
   <source>
    <other>
     <title>Katalog von 3356 Schwachen Sternen fuer das Aequinoktium 1950
+89 degrees</title>
     <author>
      <initial>J</initial>
      <lastName>Larink</lastName>
     </author>
     <author>
      <initial>A</initial>
      <lastName>Bohrmann</lastName>
     </author>
     <author>
      <initial>H</initial>
      <lastName>Kox</lastName>
     </author>
     <author>
      <initial>J</initial>
      <lastName>Groeneveld</lastName>
     </author>
     <author>
      <initial>H</initial>
      <lastName>Klauder</lastName>
     </author>
     <name>Verlag der Sternwarte, Hamburg-Bergedorf</name>
     <publisher>???</publisher>
     <city>???</city>
     <date>
      <year>1955</year>
     </date>
     <bibcode>1955</bibcode>
    </other>
   </source>
  </reference>
  <keywords parentListURL="http://messier.gsfc.nasa.gov/xml/keywordlists/adc_keywords.html">
   <keyword xlink:href="Fundamental_catalog.html">Fundamental catalog</keyword>
   <keyword xlink:href="Positional_data.html">Positional data</keyword>
   <keyword xlink:href="Proper_motions.html">Proper motions</keyword>
  </keywords>
  <descriptions>
   <description>
    <para>This catalog of 3356 faint stars was derived from meridian circle
   observations at the Bergedorf and Heidelberg Observatories. The
   positions are given for the equinox 1950 on the FK3 system. The stars
   are mainly between 8.0 and 10.0 visual magnitude. A few are brighter
   than 8.0 mag. The lower limit in brightness resulted from the visibility
   of the stars.</para>
   </description>
   <details>
    <para>All stars were observed at both the Heidelberg and Bergedorf
   Observatories. Normally, at each observatory, two observations were
   obtained with the clamp east and two with the clamp west. The mean
   errors are comparable for the two observatories with no significant
   systematic difference in the positions between them. The mean errors of
   the resulting positions should be approximated 0.011s/cos(dec) in right
   ascension and ).023" in declination.</para>
    <para>The proper motions were derived from a comparison with the catalog
   positions with the positions in the AGK2 and AGK2A with a 19 year
   baseline and from a comparison of new positions with those in Kuestner
   1900 with about a fifty year baseline.</para>
    <para>The magnitudes were taken from the AGK2. Most spectral types were
   determined by A. N. Vyssotsky. A few are from the Bergedorfer
   Spektraldurchmusterung.</para>
   </details>
  </descriptions>
  <tableHead>
   <tableLinks>
    <tableLink xlink:href="catalog.dat">
     <title>The catalog</title>
    </tableLink>
   </tableLinks>
   <fields>
    <field>
     <name>ID</name>
     <definition>Catalog number</definition>
     <units>---</units>
    </field>
    <field>
     <name>DMz</name>
     <definition>BD zone</definition>
     <units>---</units>
    </field>
    <field>
     <name>DMn</name>
     <definition>BD number</definition>
     <units>---</units>
    </field>
    <field>
     <name>mag</name>
     <definition>Photographic magnitude</definition>
     <units>mag</units>
    </field>
    <field>
     <name>Sp</name>
     <definition>Spectral class</definition>
     <units>---</units>
    </field>
    <field>
     <name>RAh</name>
     <definition>Right Ascension hours (1950)</definition>
     <units>h</units>
    </field>
    <field>
     <name>RAm</name>
     <definition>Right Ascension minutes (1950)</definition>
     <units>min</units>
    </field>
    <field>
     <name>RAs</name>
     <definition>Right Ascension seconds (1950)</definition>
     <units>s</units>
    </field>
    <field>
     <name>Pr-RA1</name>
     <definition>First order precession in RA per century</definition>
     <units>0.01s/a</units>
    </field>
    <field>
     <name>Pr-RA2</name>
     <definition>Second order precession in RA per century</definition>
     <units>0.0001s2/a2</units>
    </field>
    <field>
     <name>pmRA</name>
     <definition>Proper motion in RA from AGK2 positions</definition>
     <units>0.01s/a</units>
    </field>
    <field>
     <name>pmRA2</name>
     <definition>Proper motion in RA from Kuestner positions</definition>
     <units>0.01s/a</units>
    </field>
    <field>
     <name>DE-</name>
     <definition>Sign of declination (1950)</definition>
     <units>---</units>
    </field>
    <field>
     <name>DEd</name>
     <definition>Declination degrees (1950)</definition>
     <units>deg</units>
    </field>
    <field>
     <name>DEm</name>
     <definition>Declination minutes (1950)</definition>
     <units>arcmin</units>
    </field>
    <field>
     <name>DEs</name>
     <definition>Declination seconds (1950)</definition>
     <units>arcsec</units>
    </field>
    <field>
     <name>Pr-de1</name>
     <definition>First order precession in dec per century</definition>
     <units>arcsec/ha</units>
    </field>
    <field>
     <name>Pr-de2</name>
     <definition>Second order precession in dec per century</definition>
     <units>arcsec2/ha2</units>
    </field>
    <field>
     <name>pmdec</name>
     <definition>Proper motion in DE from AGK2 positions</definition>
     <units>arcsec/ha</units>
    </field>
    <field>
     <name>pmdec2</name>
     <definition>Proper motion in DE from Kuestner positions</definition>
     <units>arcsec/ha</units>
    </field>
    <field>
     <name>epoch</name>
     <definition>Epoch of observation - 1900.0</definition>
     <units>yr</units>
    </field>
    <field>
     <name>rem</name>
     <definition>Note for star in printed catalog
      <footnote>
       <para>1 = ma (blend?)
   3 = pr (preceding)
   4 = seq (following)
   5 = bor (northern)
   6 = au (southern)
   * = other note in printed volume (All notes in the printed volume have not
       been indicated in this version.)
   the printed volume sometimes has additional information on the systems with
   numerical remarks.</para>
      </footnote>
     </definition>
     <units>---</units>
    </field>
   </fields>
  </tableHead>
  <history>
   <ingest>
    <creator>
     <lastName>Nancy Grace Roman</lastName>
     <affiliation>ADC/SSDOO</affiliation>
    </creator>
    <date>
     <year>1996</year>
     <month>Feb</month>
     <day>01</day>
    </date>
   </ingest>
  </history>
  <identifier>I_16.xml</identifier>
 </dataset>
</datasets>

【讨论】：

我不想展平嵌套结构，我想访问它们。我的目标是将相同的结构转换为 JSON，btu 将每个 XML 行拆分为 JSON 文件

在分解 xml elelemts 并读取之后，您可以使用 jackson 解析器在您想要的任何层次结构中重新构建 json 嵌套结构......不是吗？