1. Zuhause
  2. Frage und Antwort
  3. Wie zu implementieren XQL Join mit JAVA?

Wie zu implementieren XQL Join mit JAVA?

2016-05-09 11 views
0

Ich bin ziemlich neu in XQL und studierte kürzlich XQL Joins (Join auf XML-Dokumente) hier: - http://www.ibiblio.org/xql/xql-proposal.html#Joins. Ich habe mich nur gefragt, ob ich, wenn ich ein XQL Join in JAVA implementieren möchte, wie kann ich das mit JAVA tun?Wie zu implementieren XQL Join mit JAVA?

Join ist eine neue Funktion von XQL. Ich habe versucht, XQL-Join-Beispiele in XQuery- und XPath-APIs in JAVA zu suchen, habe aber nichts gefunden (ab sofort), um XQL-Join zu unterstützen.

Ein Beispiel für XQL verbinden ist wie folgt: -

Angenommen, wir haben eine Quelle für Bücher und eine Quelle der Bewertungen: -

<book> 
    <isbn> 84-7169-020-9 </isbn> 
    <title> Tales of the Alhambra </title> 
    <author> Washington Irving </author> 
</book> 

<review> 
    <isbn> 84-7169-020-9 </isbn> 
    <title> Tales of the Alhambra </title> 
    <reviewer> Ricardo Sanchez </reviewer> 
    <comments> 
    A romantic and humorous account of the time that 
    the author of "The Legend of Sleepy Hollow" lived 
    in an Arabian palace in Spain. 
    </comments> 
</review>

Wir möchten diese kombinieren, um eine Ansicht zu erstellen das Buch, das fand die Kommentare in Bewertungen enthält:

<book> 
    <isbn> 84-7169-020-9 </isbn> 
    <title> Tales of the Alhambra </title> 
    <author> Washington Irving </author> 

    <review> 
    <reviewer> Ricardo Sanchez </reviewer> 
    <comments> 
      A romantic and humorous account of the time that 
      the author of "The Legend of Sleepy Hollow" lived 
      in an Arabian palace in Spain. 
    </comments> 
    </review> 
</book>

um das zu erreichen, wir folgende XQL Abfrage kann schreiben: -

Obwohl ich keine solche Unterstützung in XPath und XQuery APIs in JAVA gefunden habe, aber noch aus Gründen des Versuchs, habe ich das gleiche mit XPath JAVA API versucht. Die Details sind wie folgt: -

Die XML wird in einer Testdatei (books.txt) gehalten, die die folgenden Daten enthält: -

<?xml version="1.0"?> 

<catalog> 

    <book> 
    <isbn>0470192747</isbn> 
    <author>Kay, Michael</author> 
    <title>XSLT 2.0 and XPath 2.0 (4th Edition)</title> 
    <genre>Computer</genre> 
    <price>33.99</price> 
    <publish_date>2008-06-03</publish_date> 
    <description>This book is primarily a practical reference 
    book for professional XSLT developers.</description> 
    </book> 

    <book> 
    <isbn>0596006349</isbn> 
    <author>Walmsley, Priscilla</author> 
    <title>XQuery</title> 
    <genre>Computer</genre> 
    <price>38.50</price> 
    <publish_date>2007-03-30</publish_date> 
    <description>This in-depth tutorial not only walks you through 
    the XQuery specification, but also teaches you how to program with 
    this widely anticipated query language.</description> 
    </book> 

    <book> 
    <isbn>059652112X</isbn> 
    <author>Kalin, Martin</author> 
    <title>Java Web Services: Up and Running</title> 
    <genre>Computer</genre> 
    <price>26.99</price> 
    <publish_date>2009-02-23</publish_date> 
    <description>With this example-driven book, you get a quick, practical, 
    and thorough introduction to Java's API for XML Web Services (JAX-WS) 
    and the Java API for RESTful Web Services (JAX-RS).</description> 
    </book> 

    <book> 
    <isbn>0321356683</isbn> 
    <author>Bloch, Joshua</author> 
    <title>Effective Java (2nd Edition)</title> 
    <genre>Computer</genre> 
    <price>35.99</price> 
    <publish_date>2008-05-22</publish_date> 
    <description>Presents the most practical, authoritative guidelines 
    available for writing efficient,well-designed programs.</description> 
    </book> 

    <book> 
    <isbn>0141014865</isbn> 
    <author>de Botton, Alain</author> 
    <title>Status Anxiety</title> 
    <genre>Philosophy</genre> 
    <price>9.99</price> 
    <publish_date>2005-01-13</publish_date> 
    <description>The author presents a universal condition of which 
    many of us suffer from called Status Anxiety, investigates it's 
    origins and possible solutions.</description> 
    </book> 

    <book> 
    <isbn>0201771861</isbn> 
    <author>Rusty Harold, Elliotte</author> 
    <title>Processing XML with Java (SAX, DOM, JDOM, JAXP &amp; TrAX)</title> 
    <genre>Computer</genre> 
    <price>37.99</price> 
    <publish_date>2002-11-14</publish_date> 
    <description>Handing and processing XML in 
    the Java programming language.</description> 
    </book> 

    <book> 
    <isbn>1887521143</isbn> 
    <author>Poomsan Becker, Benjawan</author> 
    <title>Thai-English and English-Thai Dictionary</title> 
    <genre>Dictionary</genre> 
    <price>14.95</price> 
    <publish_date>2005-04-30</publish_date> 
    <description>With Transliteration for Non-Thai Speakers - 
    Complete with Thai Alphabet Guide</description> 
    </book> 

    <book> 
    <isbn>0415071771</isbn> 
    <author>Jung, Carl Gustav</author> 
    <title>Psychological Types</title> 
    <genre>Psychology</genre> 
    <price>19.99</price> 
    <publish_date>1992-01-02</publish_date> 
    <description>Essential reading for anyone requiring a proper 
    understanding of Jung's psychology, this was the work in which Jung 
    set out his theory of psychological types as a means of understanding 
    ourselves and the world around us.</description> 
    </book> 

    <book> 
    <isbn>0596003552</isbn> 
    <author>Pawson, Dave</author> 
    <title>XSL-FO: Making XML Look Good in Print</title> 
    <genre>Computer</genre> 
    <price>26.99</price> 
    <publish_date>2002-08-19</publish_date> 
    <description>Outlines XSL FO's strengths and weaknesses, provides 
    a tutorial and reference guide.</description> 
    </book> 

    <book> 
    <isbn>0321392795</isbn> 
    <author>Gray, Simon</author> 
    <title>Data Structures in Java</title> 
    <genre>Computer</genre> 
    <price>53.99</price> 
    <publish_date>2006-11-13</publish_date> 
    <description>From Abstract Data Types to the 
    Java Collections Framework.</description> 
    </book> 

    <review> 
     <isbn>0321392795</isbn> 
     <title> Tales of the Alhambra </title> 
     <reviewer> Ricardo Sanchez </reviewer> 
     <comments> 
     A romantic and humorous account of the time that 
     the author of "The Legend of Sleepy Hollow" lived 
     in an Arabian palace in Spain. 
     </comments> 
    </review> 

</catalog>

Der JAVA-Code für die Implementierung ist wie folgt: -

import java.io.File; 
import java.io.IOException; 

import javax.xml.parsers.DocumentBuilderFactory; 
import javax.xml.parsers.DocumentBuilder; 
import javax.xml.parsers.ParserConfigurationException; 
import javax.xml.xpath.XPath; 
import javax.xml.xpath.XPathConstants; 
import javax.xml.xpath.XPathExpressionException; 
import javax.xml.xpath.XPathFactory; 

import org.w3c.dom.Document; 
import org.w3c.dom.NodeList; 
import org.w3c.dom.Node; 
import org.w3c.dom.Element; 
import org.xml.sax.SAXException; 

public class XQLJoin { 

    public static void main(String[] args) { 

     try { 
     File inputFile = new File("books.txt"); 
     DocumentBuilderFactory dbFactory 
      = DocumentBuilderFactory.newInstance(); 
     DocumentBuilder dBuilder; 

     dBuilder = dbFactory.newDocumentBuilder(); 

     Document doc = dBuilder.parse(inputFile); 
     doc.getDocumentElement().normalize(); 

     XPath xPath = XPathFactory.newInstance().newXPath(); 

     String expression = "/catalog/book[isbn][$i:=isbn] { $i | title | author | //review[isbn=$i] { reviewer | comments }}";   
     NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(doc, XPathConstants.NODESET); 
     for (int i = 0; i < nodeList.getLength(); i++) { 
      Node nNode = nodeList.item(i); 
      System.out.println("\nCurrent Element :" 
       + nNode.getNodeName()); 
      if (nNode.getNodeType() == Node.ELEMENT_NODE) { 
       Element eElement = (Element) nNode; 
       System.out.println("Title : " 
        + eElement 
        .getElementsByTagName("title") 
        .item(0) 
        .getTextContent()); 
       System.out.println("Reviewer : " 
        + eElement 
        .getElementsByTagName("reviewer") 
        .item(0) 
        .getTextContent()); 
      } 
     } 
     } catch (ParserConfigurationException e) { 
     e.printStackTrace(); 
     } catch (SAXException e) { 
     e.printStackTrace(); 
     } catch (IOException e) { 
     e.printStackTrace(); 
     } catch (XPathExpressionException e) { 
     e.printStackTrace(); 
     } 
    } 
}

der obige Code hat eine Ausnahme mit dem folgenden Stack Trace: -

javax.xml.transform.TransformerException: Expected ], but found: isbn 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.error(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.consumeExpected(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.Predicate(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.Step(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.RelativeLocationPath(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.LocationPath(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.PathExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.UnionExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.UnaryExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.MultiplicativeExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.AdditiveExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.RelationalExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.EqualityExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.AndExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.OrExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.Expr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.initXPath(Unknown Source) 
    at com.sun.org.apache.xpath.internal.XPath.<init>(Unknown Source) 
    at com.sun.org.apache.xpath.internal.XPath.<init>(Unknown Source) 
    at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.compile(Unknown Source) 
    at XQLJoin.main(XQLJoin.java:36) 
--------------- linked to ------------------ 
javax.xml.xpath.XPathExpressionException: javax.xml.transform.TransformerException: Expected ], but found: isbn 
    at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.compile(Unknown Source) 
    at XQLJoin.main(XQLJoin.java:36) 
Caused by: javax.xml.transform.TransformerException: Expected ], but found: isbn 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.error(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.consumeExpected(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.Predicate(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.Step(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.RelativeLocationPath(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.LocationPath(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.PathExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.UnionExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.UnaryExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.MultiplicativeExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.AdditiveExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.RelationalExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.EqualityExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.AndExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.OrExpr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.Expr(Unknown Source) 
    at com.sun.org.apache.xpath.internal.compiler.XPathParser.initXPath(Unknown Source) 
    at com.sun.org.apache.xpath.internal.XPath.<init>(Unknown Source) 
    at com.sun.org.apache.xpath.internal.XPath.<init>(Unknown Source) 
    ... 2 more

Bitte schlagen vor, wie diese Funktionalität mit Java implementiert wird. Irgendwelche Hinweise ?

Quelle

2016-05-09 user6276653

Antwort

1

Beginnen wir zuerst mit XQL; XQL ist veraltet, so weit ich weiß, dass es keine aktuellen Implementierungen gibt, glaube ich, dass XQL ein Vorläufer von XQuery war, also sollten Sie wirklich von XQuery 3.1 ausgehen, anstatt sich um XQL zu sorgen.

Das besagt, XQuery fehlt die explizite Joins in XQL beschrieben. XQuery bietet die Möglichkeit zum Erstellen von Joins, aber es gibt keine implizite Zusammenführung der Ergebnisse. Sie können die Ergebnisse unter Verwendung von 1 von 3 Methoden explizit zusammenführen, die sofort in den Sinn kommen:

  1. XQuery Update das Ergebnis der ersten Abfrage zu nehmen und das Ergebnis der Verknüpfung einfügen.
  2. Eine identity transform auf das Ergebnis der ersten Abfrage, injizieren das Ergebnis der Join.
  3. Mithilfe von Elementkonstruktoren geben Sie die gewünschte XML-Form aus und platzieren die Abfragen in dieser Struktur (siehe unten).

Das Problem mit dem Code oben ist, dass Ihr XPath ungültig ist, was genau das ist, was der Fehler, den Sie Sie empfangen erzählt, dh [$i:=isbn] ist das ursprüngliche Problem, aber dann der {{ Teil ist nicht gültig XPath oder XQuery entweder.

Für einen XQuery-Ausdruck tun, was Sie suchen, werde ich für Anfänger (dh Option 3 von oben) vielleicht den einfacheren Ansatz vorstellen:

<catalog> 
{ 
    for $book in /catalog/book 
    let $reviews := /catalog/review[isbn eq $book/isbn] 
    return 
     <book> 
     { 
      $book/*, 
      for $review in $reviews 
      return 
       <review> 
       { 
        $review/(reviewer | comments) 
       } 
       </review> 
     } 
     </book> 
} 
</catalog>

Dies wird die folgende Ausgabe (von der Quelle erzeugen Dokument, das Sie in Ihrer Frage beschrieben):

<?xml version="1.0" encoding="UTF-8"?> 
<catalog> 
    <book> 
     <isbn>0470192747</isbn> 
     <author>Kay, Michael</author> 
     <title>XSLT 2.0 and XPath 2.0 (4th Edition)</title> 
     <genre>Computer</genre> 
     <price>33.99</price> 
     <publish_date>2008-06-03</publish_date> 
     <description>This book is primarily a practical reference 
      book for professional XSLT developers.</description> 
    </book> 
    <book> 
     <isbn>0596006349</isbn> 
     <author>Walmsley, Priscilla</author> 
     <title>XQuery</title> 
     <genre>Computer</genre> 
     <price>38.50</price> 
     <publish_date>2007-03-30</publish_date> 
     <description>This in-depth tutorial not only walks you through 
      the XQuery specification, but also teaches you how to program with 
      this widely anticipated query language.</description> 
    </book> 
    <book> 
     <isbn>059652112X</isbn> 
     <author>Kalin, Martin</author> 
     <title>Java Web Services: Up and Running</title> 
     <genre>Computer</genre> 
     <price>26.99</price> 
     <publish_date>2009-02-23</publish_date> 
     <description>With this example-driven book, you get a quick, practical, 
      and thorough introduction to Java's API for XML Web Services (JAX-WS) 
      and the Java API for RESTful Web Services (JAX-RS).</description> 
    </book> 
    <book> 
     <isbn>0321356683</isbn> 
     <author>Bloch, Joshua</author> 
     <title>Effective Java (2nd Edition)</title> 
     <genre>Computer</genre> 
     <price>35.99</price> 
     <publish_date>2008-05-22</publish_date> 
     <description>Presents the most practical, authoritative guidelines 
      available for writing efficient,well-designed programs.</description> 
    </book> 
    <book> 
     <isbn>0141014865</isbn> 
     <author>de Botton, Alain</author> 
     <title>Status Anxiety</title> 
     <genre>Philosophy</genre> 
     <price>9.99</price> 
     <publish_date>2005-01-13</publish_date> 
     <description>The author presents a universal condition of which 
      many of us suffer from called Status Anxiety, investigates it's 
      origins and possible solutions.</description> 
    </book> 
    <book> 
     <isbn>0201771861</isbn> 
     <author>Rusty Harold, Elliotte</author> 
     <title>Processing XML with Java (SAX, DOM, JDOM, JAXP &amp; TrAX)</title> 
     <genre>Computer</genre> 
     <price>37.99</price> 
     <publish_date>2002-11-14</publish_date> 
     <description>Handing and processing XML in 
      the Java programming language.</description> 
    </book> 
    <book> 
     <isbn>1887521143</isbn> 
     <author>Poomsan Becker, Benjawan</author> 
     <title>Thai-English and English-Thai Dictionary</title> 
     <genre>Dictionary</genre> 
     <price>14.95</price> 
     <publish_date>2005-04-30</publish_date> 
     <description>With Transliteration for Non-Thai Speakers - 
      Complete with Thai Alphabet Guide</description> 
    </book> 
    <book> 
     <isbn>0415071771</isbn> 
     <author>Jung, Carl Gustav</author> 
     <title>Psychological Types</title> 
     <genre>Psychology</genre> 
     <price>19.99</price> 
     <publish_date>1992-01-02</publish_date> 
     <description>Essential reading for anyone requiring a proper 
      understanding of Jung's psychology, this was the work in which Jung 
      set out his theory of psychological types as a means of understanding 
      ourselves and the world around us.</description> 
    </book> 
    <book> 
     <isbn>0596003552</isbn> 
     <author>Pawson, Dave</author> 
     <title>XSL-FO: Making XML Look Good in Print</title> 
     <genre>Computer</genre> 
     <price>26.99</price> 
     <publish_date>2002-08-19</publish_date> 
     <description>Outlines XSL FO's strengths and weaknesses, provides 
      a tutorial and reference guide.</description> 
    </book> 
    <book> 
     <isbn>0321392795</isbn> 
     <author>Gray, Simon</author> 
     <title>Data Structures in Java</title> 
     <genre>Computer</genre> 
     <price>53.99</price> 
     <publish_date>2006-11-13</publish_date> 
     <description>From Abstract Data Types to the 
      Java Collections Framework.</description> 
     <review> 
     <reviewer> Ricardo Sanchez </reviewer> 
     <comments> 
      A romantic and humorous account of the time that 
      the author of "The Legend of Sleepy Hollow" lived 
      in an Arabian palace in Spain. 
     </comments> 
     </review> 
    </book> 
</catalog>

Wenn Sie dies als Ihre expression oben verwenden, sollten Sie gut sein :-) zu gehen

Quelle

2016-05-09 21:33:29 adamretter

 Verwandte Themen

  • Keine verwandten Themen^_^