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xquery语法

脚踏实地 — Wed, 07 Oct 2009 09:51:00 GMT

xquery语法

脚踏实地 2009-10-07 17:51 发表评论

脚踏实地 — Wed, 07 Oct 2009 09:46:00 GMT

一些基本的语法规则�Q?/span>

· XQuery对大��写敏感

· XQuery的元素、属性以�?qi��ng)变量必��L��合法的XML名称�?

· XQuery字符串值可使用单引��h��双引受��?

· XQuery变量�?#8220;$”�q�跟随一个名�U�来�q�行定义�Q��D例，$bookstore

· XQuery注释�?:�?)分割�Q��D例，(: XQuery 注释 :)

XQuery 条�g表达�?/span>

"If-Then-Else"可以在XQuery中��用�?/span>

��L(f��ng)��下面的例子：(x��)

for $x in doc("books.xml")/bookstore/book

return if ($x/@category="CHILDREN")

then {data($x/title)}

else {data($x/title)}

��h��?If-Then-Else"的语法：(x��)if表达式后的圆括号是必需的。else也是必需的，不过仅仅�?#8220;else ()”也是可以的�?/span>

上面的例子的�l�果�Q?/span>

Everyday Italian

Harry Potter

Learning XML

XQuery Kick Start

XQuery 比较

�?span lang="EN-US">XQuery中，有两�U�方法来比较倹{�?br />

1. 通用比较�Q?span lang="EN-US">=, !=, <, <=, >, >=

2. 值的比较�Q�eq、ne、lt、le、gt、ge

��L(f��ng)��下面�?span lang="EN-US">XQuery表达式：(x��)

$bookstore//book/@q > 10

如果q属性的值大�?span lang="EN-US">10�Q�上面的表达式的�q�回��gؓ(f��)true�?span lang="EN-US">

$bookstore//book/@q gt 10

如果仅返回一�?span lang="EN-US">q�Q�且它的值大�?span lang="EN-US">10�Q�那么表辑ּ��q�回true。如果不止一�?span lang="EN-US">q被返回，则会(x��)发生错误�?span lang="EN-US">

向结果添加元素和属�?/span>

正如在前面一节看到的�Q�我们可以在�l�果中引用输入文件中的元素和属性：(x��)

for $x in doc("books.xml")/bookstore/book/title

order by $x

return $x

上面的XQuery表达式会(x��)在结果中引用title元素和lang属性，��像�q�样�Q?

Everyday Italian

Harry Potter

Learning XML

XQuery Kick Start

以上XQuery表达式返回title元素的方式和它们在输入文档中被描�q�的方式的相同的�?/span>

现在我们要向�l�果��d��我们自己的元素和属性！

��d��HTML元素和文�?/span>

现在�Q�我们要向结果添加HTML元素。我们会(x��)把结果放在一个HTML列表�?- Now, we want to add some HTML elements to the result. We will put the result in an HTML list - together with some text:

Bookstore

{

for $x in doc("books.xml")/bookstore/book

order by $x/title

return

{data($x/title)}. Category: {data($x/@category)}

}

以上XQuery表达式会(x��)生成下面的结果：(x��)

Bookstore

Everyday Italian. Category: COOKING

Harry Potter. Category: CHILDREN

Learning XML. Category: WEB

XQuery Kick Start. Category: WEB

选择和过滤元�?/span>

正如在前面的章节看到的，我们使用路径表达式或FLWOR表达式来选去和过滤元素�?/span>

��L(f��ng)��下面的FLWOR表达式：(x��)

for $x in doc("books.xml")/bookstore/book

where $x/price>30

order by $x/title

return $x/title

for

�Q�可选）向每个由in表达式返回的��目捆绑一个变�?/span>

let

�Q�可选）

where

�Q�可选）讑֮�一个条�?/span>

order by

�Q�可选）讑֮��l�果的排列顺�?/span>

return

规定在结果中�q�回的内�?

for 语句

for语句可将变量捆绑到由in表达式返回的每个��目。for可��生�P代。在同一个FLWOR表达式中可存在多重for语句�?/span>

如需在一个for语句中��@环指定的�ơ数�Q��?zh��n)�可��?em>关键词to�Q?

for $x in (1 to 5)

return {$x}

�l�果�Q?/span>

关键词at可被用来计算�q�代�Q?/span>

for $x at $i in doc("books.xml")/bookstore/book/title

return {$i}. {data($x)}

�l�果�Q?/span>

1. Everyday Italian

2. Harry Potter

3. XQuery Kick Start

4. Learning XML

在for语句中同�?em>允许多个in表达�?/em>。请使用逗号来分割每一个in表达式：(x��)

for $x in (10,20), $y in (100,200)

return x={$x} and y={$y}

�l�果�Q?/span>

x=10 and y=100

x=10 and y=200

x=20 and y=100

x=20 and y=200

let 语句

let语句可完成变量分配，�q�可避免多次重复相同的表辑ּ�。let语句不回��D��q�代�?/span>

let $x := (1 to 5)

return {$x}

�l�果

1 2 3 4 5

where 语句

where语句用于为结果设定一个或多个条�g�Q�criteria�Q��?/span>

where $x/price>30 and $x/price<100

order by 语句

order by语句用于规定�l�果的排序次序。此处，我们要根据category和title来对�l�果�q�行排序�Q?/span>

for $x in doc("books.xml")/bookstore/book

order by $x/@category, $x/title

return $x/title

�l�果�Q?/span>

Harry Potter

Everyday Italian

Learning XML

XQuery Kick Start

return 语句�Q?/span>

return语句规定要返回的内容�?/span>

for $x in doc("books.xml")/bookstore/book

return $x/title

�l�果�Q?/span>

Everyday Italian

Harry Potter

XQuery Kick Start

Learning XML

脚踏实地 2009-10-07 17:46 发表评论

脚踏实地 — Wed, 07 Oct 2009 09:26:00 GMT

在介�l�语法的时候，例子中��用的XML文档�?/span>"books.xml":

            Everyday Italian
            Giada De Laurentiis
            2005
            30.00

            Harry Potter
            J K. Rowling
            2005
            29.99

            XQuery Kick Start
            James McGovern
            Per Bothner
            Kurt Cagle
            James Linn
            Vaidyanathan Nagarajan
            2003
            49.99

            Learning XML
            Erik T. Ray
            2003
            39.95

一、函�?/span>

XQuery使用函数来提取XML文档中的数据�?/span>

doc()用于打开"books.xml"文�g�Q?/span>

doc("books.xml")

二、�\径表辑ּ�

XQuery使用路径表达式在XML文档中通过元素�q�行��D��?/span>

下面的�\径表辑ּ�用于�?books.xml"文�g中选取所有的title元素�Q?/span>

doc("books.xml")/bookstore/book/title

(/bookstore选取bookstore元素�Q?book选取bookstore元素下的所有book元素�Q��?title选取每个book元素下的所有title元素)

上面的XQuery可提取以下数据：(x��)

Everyday Italian

Harry Potter

XQuery Kick Start

Learning XML

三、谓�?/span>

XQuery使用谓语来限定从XML文档所提取的数据�?/span>

下面的谓语用于选取bookstore元素下的所有book元素�Q��ƈ且所选取的book元素下的price元素的值必��d��?0�Q?/span>

doc("books.xml")/bookstore/book[price<30]

上面的XQuery可提取到下面的数据：(x��)

Harry Potter

J K. Rowling

2005

29.99

四�?span style="font-size: 13.5pt; font-family: 宋体; mso-bidi-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">使用FLWOR�?span lang="EN-US">"books.xml"选取节点

FLWOR�?span lang="EN-US">"For, Let, Where, Order by, Return"的只取首字母�~�写�?/span>

for语句�?span lang="EN-US">bookstore元素下的所�?span lang="EN-US">book元素提取到名�?span lang="EN-US">$x的变量中�?span lang="EN-US">

where语句选取�?span lang="EN-US">price元素值大�?span lang="EN-US">30�?span lang="EN-US">book元素�?span lang="EN-US">

order by语句定义了排序次序。将�Ҏ(gu��)��title元素�q�行排序�?span lang="EN-US">

return语句规定�q�回什么内宏V��在此返回的�?span lang="EN-US">title元素�?br />

��L(f��ng)��下面�q�个路径表达式：(x��)

doc("books.xml")/bookstore/book[price>30]/title

上面�q�个表达式可选取bookstore元素下的book元素下所有的title元素�Q��ƈ且其中的price元素的值必��d��?0�?/span>

下面�q�个FLWOR表达式所选取的数据和上面的�\径表辑ּ�是相同的�Q?/span>

for $x in doc("books.xml")/bookstore/book

where $x/price>30

return $x/title

�l�果是：(x��)

XQuery Kick Start

Learning XML

通过FLWOR�Q��?zh��n)�可以对结果进行排序�?x��)

for $x in doc("books.xml")/bookstore/book

where $x/price>30

order by $x/title

return $x/title

上面�?span lang="EN-US">XQuery表达式的�l�果�Q?span lang="EN-US">

Learning XML

XQuery Kick Start

在一个HTML列表中提交结�?/span>

��L(f��ng)��下面的XQuery FLWOR表达式：(x��)

for $x in doc("books.xml")/bookstore/book/title

order by $x

return $x

上面的表辑ּ��?x��)选取bookstore元素下的book元素下的所有title元素�Q��ƈ以字母顺序返回title元素�?/span>

现在�Q�我们希望��用HTML列表列出我们的书店中所有的书目。我们向FLWOR表达式添�?lt;ul>�?lt;li>标签�Q?/span>

{

for $x in doc("books.xml")/bookstore/book/title

order by $x

return

{$x}

}

以上代码的结果：(x��)

Everyday Italian

Harry Potter

Learning XML

XQuery Kick Start

现在我们希望去除title元素�Q�而仅仅显�C�title元素内的数据�?/span>

{

for $x in doc("books.xml")/bookstore/book/title

order by $x

return

{data($x)}

}

�l�果��是一个HTML列表�Q?/span>

Everyday Italian

Harry Potter

Learning XML

XQuery Kick Start

脚踏实地 2009-10-07 17:26 发表评论

脚踏实地 — Wed, 07 Oct 2009 09:14:00 GMT

一、��用eclipse新徏一个java project
二、把saxon的jar包放入classpath�Q�我用的jar包是saxon9ee.jar�Q?br /> 三、新建package�Q�然后新��Z��个xml文�g�Q�cd_catalog.xml�Q?其内容如下：(x��)



              Empire Burlesque
              Bob Dylan
              USA
               Columbia
              10.90
              1985


              Hide your heart
              Bonnie Tyler
              UK
              CBS Records
              9.90
              1988


              Greatest Hits
              Dolly Parton
              USA
              RCA
              9.90
              1982


              Still got the blues
              Gary Moore
              UK
              Virgin records
              10.20
              1990


              Eros
              Eros Ramazzotti
              EU
              BMG
              9.90
              1997


              One night only
              Bee Gees
              UK
              Polydor
              10.90
              1998


              Sylvias Mother
              Dr.Hook
              UK
              CBS
              8.10
              1973


                Maggie May
              Rod Stewart
              UK
              Pickwick
              8.50
              1990


               Romanza
              Andrea Bocelli
              EU
              Polydor
              10.80
              1996


              When a man loves a woman
              Percy Sledge
              USA
              Atlantic
              8.70
              1987



四、新��Z��个java class�Q�XqueryTest.java�Q?

import java.io.IOException;
import java.util.Properties;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.xml.sax.SAXException;

import net.sf.saxon.Configuration;
import net.sf.saxon.dom.*;
import net.sf.saxon.query.DynamicQueryContext;
import net.sf.saxon.query.StaticQueryContext;
import net.sf.saxon.query.XQueryExpression;
import net.sf.saxon.trans.XPathException;

public class XqueryTest {
/**
* 执行查询
*/
public static void select(){
  //文�g
  String fileString = "src/study/xquery/cd_catalog.xml";
  //查询语句
  String query = " for $s in //CD/TITLE "
    + " return $s";
  //生��文档对象
  Document document = getDocument(fileString);
  Configuration configuration = new Configuration();
  StaticQueryContext context = new StaticQueryContext(configuration, false);
  //查询表达式对�?br />   XQueryExpression expression = null;
  try {
   expression = context.compileQuery(query);
   DynamicQueryContext context2 = new DynamicQueryContext(configuration);
   context2.setContextItem(new DocumentWrapper(document,null,configuration));

   final Properties props = new Properties();
            props.setProperty(OutputKeys.METHOD, "xml");
            props.setProperty(OutputKeys.INDENT, "yes");
            //执行查询�Q��ƈ输出查询�l�果
            expression.run(context2, new StreamResult(System.out), props);
  } catch (XPathException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

}
/**
* 生��文档对象
*
* @param xml   文�g�?br /> * @return
*/
public static Document getDocument(String xml){
  DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
  DocumentBuilder builder;
  Document document = null;
  try {
   builder = builderFactory.newDocumentBuilder();
   document = builder.parse(xml);
  } catch (ParserConfigurationException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (SAXException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  document.normalize();
  return document;
}
/**
* 输入生成的文档内�?br /> *
* @param doc
*/
public static void output(Document doc){
  TransformerFactory factory = TransformerFactory.newInstance();
  Transformer transformer = null;
  try {
   transformer = factory.newTransformer();
   Properties properties = transformer.getOutputProperties();
   properties.setProperty(OutputKeys.INDENT, "yes");
            properties.setProperty(OutputKeys.ENCODING, "GB2312");
            properties.setProperty(OutputKeys.METHOD, "xml");
            properties.setProperty(OutputKeys.VERSION, "1.0");
            transformer.setOutputProperties(properties);

            DOMSource source = new DOMSource(doc);
            StreamResult result = new StreamResult(System.out);
            transformer.transform(source, result);

  } catch (TransformerConfigurationException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (TransformerException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
}
public static void main(String[] args) {
  select();
}
}

五、运行结�?br />
Empire Burlesque
Hide your heart
Greatest Hits
Still got the blues
Eros
One night only
Sylvias Mother
Maggie May
Romanza
When a man loves a woman

脚踏实地 2009-10-07 17:14 发表评论

xquery�q�行环境

脚踏实地 — Wed, 07 Oct 2009 08:55:00 GMT

要��用xquery�q�行查询�Q�需要一个xquery的处理器�Q�在此我们��用saxon处理器�?br /> Saxon是一个内存处理器。无��Z��用XSLT�q�是XQuery�Q�Saxon被设计来处理在内存中装配好的源�?/p> 用法�Q?br /> 1.下蝲saxon压羃�?br /> http://saxon.sourceforge.net/
只需要里面的jar�?br /> 2.jdk1.4以上卛_��

脚踏实地 2009-10-07 16:55 发表评论