在网络时代,XML文件起到了一个保存和传输数据的作用。Soap协议通过Xml交流信息,数据库通过Xml文件存取等等。那么怎样快速的从一个XML文件中取得所需的信息呢?
我们知道,JAVA的JAXP中和Microsoft.Net都有Xml分析器,Microsoft.Net是边读边分析,而JAXP是读到内存中然后才进行分析(还有一种是事件机制去读),总而言之,是不利于快速读取。基于此,Microsoft.Net 和JAXP都提供了XPATH机制,来快速定位到XML文件中所需的节点。
例如有一个XML文件:booksort.xml:
<?xml version="1.0"?>
<!-- a fragment of a book store inventory database -->
<bookstore xmlns:bk="urn:samples">
<book genre="novel" publicationdate="1997" bk:ISBN="1-861001-57-8">
<title>Pride And Prejudice</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>24.95</price>
</book>
<book genre="novel" publicationdate="1992" bk:ISBN="1-861002-30-1">
<title>The Handmaid's Tale</title>
<author>
<first-name>Margaret</first-name>
<last-name>Atwood</last-name>
</author>
<price>29.95</price>
</book>
<book genre="novel" publicationdate="1991" bk:ISBN="1-861001-57-6">
<title>Emma</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>19.95</price>
</book>
<book genre="novel" publicationdate="1982" bk:ISBN="1-861001-45-3">
<title>Sense and Sensibility</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>19.95</price>
</book>
</bookstore>
如果我们想快速查找”last-name”等于”Austen”的所有标题名,可以通过以下方法可以得到:
XmlReaderSample.cs
//Corelib.net/System.Xml.Xsl/XPathDocument Class
//Author :Any
using System;
using System.IO;
using System.Xml;
using System.Xml.XPath;
public class XmlReaderSample
{
public static void Main()
{
XmlTextReader myxtreader = new XmlTextReader("booksort.xml");
XmlReader myxreader = myxtreader;
XPathDocument doc = new XPathDocument(myxreader);
XPathNavigator nav = doc.CreateNavigator();
XPathExpression expr;
expr = nav.Compile("descendant::book[author/last-name='Austen']");
//expr.AddSort("title", XmlSortOrder.Ascending, XmlCaseOrder.None, "", XmlDataType.Text);
XPathNodeIterator iterator = nav.Select(expr);
while (iterator.MoveNext())
{
XPathNavigator nav2 = iterator.Current;
nav2.MoveToFirstChild();
Console.WriteLine("Book title: {0}", nav2.Value);
}
}
}
运行这个程序,结果为:
Book title: Pride And Prejudice
Book title: Emma
Book title: Sense and Sensibility
可以看到查找正确。
利用XPATH中的一些功能,也可以实现简单的排序和简单运算。如在数据库中经常要对数据进行汇总,就可用XPATH实现。
如:
order.xml
<!--Represents a customer order-->
<order>
<book ISBN='10-861003-324'>
<title>The Handmaid's Tale</title>
<price>19.95</price>
</book>
<cd ISBN='2-3631-4'>
<title>Americana</title>
<price>16.95</price>
</cd>
</order>
和:books.xml
<?xml version="1.0"?>
<!-- This file represents a fragment of a book store inventory database -->
<bookstore>
<book cc="dd" xmlns:bk="urn:sample" xmlns:ns="http://www.Any.com" genre="autobiography" publicationdate="1981" ISBN="1-861003-11-0">
<title>The Autobiography of Benjamin Franklin</title>
<ns:author>
<first-name>Benjamin</first-name>
<last-name>Franklin</last-name>
</ns:author>
<price>8.99</price>
</book>
<book genre="novel" publicationdate="1967" ISBN="0-201-63361-2">
<title>The Confidence Man</title>
<author>
<first-name>Herman</first-name>
<last-name>Melville</last-name>
</author>
<price>11.99</price>
</book>
<book genre="philosophy" publicationdate="1991" ISBN="1-861001-57-6">
<title>The Gorgias</title>
<author>
<name>Plato</name>
</author>
<price>9.99</price>
</book>
</bookstore>
我们可以对该XML文件中的price求和,以得到价格总数。
Evaluate.cs
//Corelib.net/System.Xml.Xsl/XPathNavigator Class
//Author :Any
using System;
using System.IO;
using System.Xml;
using System.Xml.XPath;
public class EvaluateSample
{
public static void Main()
{
EvaluateSample myEvaluateSample = new EvaluateSample();
myEvaluateSample.test("books.xml");
}
public void test(String args)
{
try
{
//test Evaluate(String);
XPathDocument myXPathDocument = new XPathDocument(args);
XPathNavigator myXPathNavigator = myXPathDocument.CreateNavigator();
Console.WriteLine(myXPathNavigator.Evaluate("sum(descendant::book/price)"));
//testEvaluate(XPathExpression);
XmlDocument doc = new XmlDocument();
doc.Load("order.xml");
XPathNavigator nav = doc.CreateNavigator();
XPathExpression expr = nav.Compile("sum(//price/text())");
Console.WriteLine(nav.Evaluate(expr));
//testEvaluate(XPathExpression);
XPathNodeIterator myXPathNodeIterator = nav.Select("descendant::book/title");
expr = nav.Compile("sum(//price/text())");
Console.WriteLine(nav.Evaluate(expr,myXPathNodeIterator));
}
catch (Exception e)
{
Console.WriteLine ("Exception: {0}", e.ToString());
}
}
}
运行这个程序,结果如下:
30.97
36.9
36.9
我们可以看到,30.97是books.xml中所有price值的总和,而36.9则是order.xml中所有price值的总和。通过XPAH不仅可以快速查找信息,而且还可以对信息进行一些基本的处理。
我们知道,JAVA的JAXP中和Microsoft.Net都有Xml分析器,Microsoft.Net是边读边分析,而JAXP是读到内存中然后才进行分析(还有一种是事件机制去读),总而言之,是不利于快速读取。基于此,Microsoft.Net 和JAXP都提供了XPATH机制,来快速定位到XML文件中所需的节点。
例如有一个XML文件:booksort.xml:
<?xml version="1.0"?>
<!-- a fragment of a book store inventory database -->
<bookstore xmlns:bk="urn:samples">
<book genre="novel" publicationdate="1997" bk:ISBN="1-861001-57-8">
<title>Pride And Prejudice</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>24.95</price>
</book>
<book genre="novel" publicationdate="1992" bk:ISBN="1-861002-30-1">
<title>The Handmaid's Tale</title>
<author>
<first-name>Margaret</first-name>
<last-name>Atwood</last-name>
</author>
<price>29.95</price>
</book>
<book genre="novel" publicationdate="1991" bk:ISBN="1-861001-57-6">
<title>Emma</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>19.95</price>
</book>
<book genre="novel" publicationdate="1982" bk:ISBN="1-861001-45-3">
<title>Sense and Sensibility</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>19.95</price>
</book>
</bookstore>
如果我们想快速查找”last-name”等于”Austen”的所有标题名,可以通过以下方法可以得到:
XmlReaderSample.cs
//Corelib.net/System.Xml.Xsl/XPathDocument Class
//Author :Any
using System;
using System.IO;
using System.Xml;
using System.Xml.XPath;
public class XmlReaderSample
{
public static void Main()
{
XmlTextReader myxtreader = new XmlTextReader("booksort.xml");
XmlReader myxreader = myxtreader;
XPathDocument doc = new XPathDocument(myxreader);
XPathNavigator nav = doc.CreateNavigator();
XPathExpression expr;
expr = nav.Compile("descendant::book[author/last-name='Austen']");
//expr.AddSort("title", XmlSortOrder.Ascending, XmlCaseOrder.None, "", XmlDataType.Text);
XPathNodeIterator iterator = nav.Select(expr);
while (iterator.MoveNext())
{
XPathNavigator nav2 = iterator.Current;
nav2.MoveToFirstChild();
Console.WriteLine("Book title: {0}", nav2.Value);
}
}
}
运行这个程序,结果为:
Book title: Pride And Prejudice
Book title: Emma
Book title: Sense and Sensibility
可以看到查找正确。
利用XPATH中的一些功能,也可以实现简单的排序和简单运算。如在数据库中经常要对数据进行汇总,就可用XPATH实现。
如:
order.xml
<!--Represents a customer order-->
<order>
<book ISBN='10-861003-324'>
<title>The Handmaid's Tale</title>
<price>19.95</price>
</book>
<cd ISBN='2-3631-4'>
<title>Americana</title>
<price>16.95</price>
</cd>
</order>
和:books.xml
<?xml version="1.0"?>
<!-- This file represents a fragment of a book store inventory database -->
<bookstore>
<book cc="dd" xmlns:bk="urn:sample" xmlns:ns="http://www.Any.com" genre="autobiography" publicationdate="1981" ISBN="1-861003-11-0">
<title>The Autobiography of Benjamin Franklin</title>
<ns:author>
<first-name>Benjamin</first-name>
<last-name>Franklin</last-name>
</ns:author>
<price>8.99</price>
</book>
<book genre="novel" publicationdate="1967" ISBN="0-201-63361-2">
<title>The Confidence Man</title>
<author>
<first-name>Herman</first-name>
<last-name>Melville</last-name>
</author>
<price>11.99</price>
</book>
<book genre="philosophy" publicationdate="1991" ISBN="1-861001-57-6">
<title>The Gorgias</title>
<author>
<name>Plato</name>
</author>
<price>9.99</price>
</book>
</bookstore>
我们可以对该XML文件中的price求和,以得到价格总数。
Evaluate.cs
//Corelib.net/System.Xml.Xsl/XPathNavigator Class
//Author :Any
using System;
using System.IO;
using System.Xml;
using System.Xml.XPath;
public class EvaluateSample
{
public static void Main()
{
EvaluateSample myEvaluateSample = new EvaluateSample();
myEvaluateSample.test("books.xml");
}
public void test(String args)
{
try
{
//test Evaluate(String);
XPathDocument myXPathDocument = new XPathDocument(args);
XPathNavigator myXPathNavigator = myXPathDocument.CreateNavigator();
Console.WriteLine(myXPathNavigator.Evaluate("sum(descendant::book/price)"));
//testEvaluate(XPathExpression);
XmlDocument doc = new XmlDocument();
doc.Load("order.xml");
XPathNavigator nav = doc.CreateNavigator();
XPathExpression expr = nav.Compile("sum(//price/text())");
Console.WriteLine(nav.Evaluate(expr));
//testEvaluate(XPathExpression);
XPathNodeIterator myXPathNodeIterator = nav.Select("descendant::book/title");
expr = nav.Compile("sum(//price/text())");
Console.WriteLine(nav.Evaluate(expr,myXPathNodeIterator));
}
catch (Exception e)
{
Console.WriteLine ("Exception: {0}", e.ToString());
}
}
}
运行这个程序,结果如下:
30.97
36.9
36.9
我们可以看到,30.97是books.xml中所有price值的总和,而36.9则是order.xml中所有price值的总和。通过XPAH不仅可以快速查找信息,而且还可以对信息进行一些基本的处理。
免责声明:本站文章均来自网站采集或用户投稿,网站不提供任何软件下载或自行开发的软件!
如有用户或公司发现本站内容信息存在侵权行为,请邮件告知! 858582#qq.com
暂无“怎样快速从一个XML文件中查找信息”评论...
更新动态
20240517
20240517
- 刘欢.2004-经典20年珍藏锦集【新索】【WAV+CUE】
- 中唱唱片群星《好歌珍藏-游子情深》2CDWAV
- CD圣经上榜天碟1995-乌仁娜-《蒙古草原之歌》[WAV+CUE].
- 【电影原声】武满彻《旭日东升》1993[WAV+CUE整轨]
- Taylor Swift《THE TORTURED POETS DEPARTMENT》[320K/MP3][148.54MB]
- Taylor Swift《THE TORTURED POETS DEPARTMENT》[FLAC/分轨][405.72MB]
- Joyce Jonathan《法式松弛感 漫步香榭丽舍》[320K/MP3][80.8MB]
- 女神异闻录5佐仓双叶coop攻略 p5r佐仓双叶对话选项攻略
- 【民谣】张智《尼勒克小镇》[FLAC]
- 林一峰2018-TRAVELOGUE4ESCAPE[香港首版][WAV+CUE]
- MollyLewis《OnTheLips》(2024)[Hi-Res96kHz_24bitFLAC]
- Joyce Jonathan《法式松弛感 漫步香榭丽舍》[FLAC/分轨][230.77MB]
- 群星《影视剧 春色寄情人 原声带》[320K/MP3][394.18MB]
- 吴牧野《强者独白II 李斯特巅峰作品选》[320K/MP3][216.01MB]
- 女神异闻录5御船千早coop攻略 p5r御船千早对话选项攻略