14

我在 XML 文件下面有这个

<book>
<person>
  <first>Kiran</first>
  <last>Pai</last>
  <age>22</age>
</person>
<person>
  <first>Bill</first>
  <last>Gates</last>
  <age>46</age>
</person>
<person>
  <first>Steve</first>
  <last>Jobs</last>
  <age>40</age>
</person>
</book>

现在从 XML 文件中读取数据的 Java 程序如下所示。

import java.io.File;
import org.w3c.dom.Document;
import org.w3c.dom.*;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException; 

public class ReadAndPrintXMLFile{

    public static void main (String argv []){
    try {

            DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
            Document doc = docBuilder.parse (new File("book.xml"));

            // normalize text representation
            doc.getDocumentElement ().normalize ();
            System.out.println ("Root element of the doc is " + 
                 doc.getDocumentElement().getNodeName());


            NodeList listOfPersons = doc.getElementsByTagName("person");
            int totalPersons = listOfPersons.getLength();
            System.out.println("Total no of people : " + totalPersons);

            for(int s=0; s<listOfPersons.getLength() ; s++){


                Node firstPersonNode = listOfPersons.item(s);
                if(firstPersonNode.getNodeType() == Node.ELEMENT_NODE){


                    Element firstPersonElement = (Element)firstPersonNode;

                    //-------
                    NodeList firstNameList = firstPersonElement.getElementsByTagName("first");
                    Element firstNameElement = (Element)firstNameList.item(0);

                    NodeList textFNList = firstNameElement.getChildNodes();
                    System.out.println("First Name : " + 
                           ((Node)textFNList.item(0)).getNodeValue().trim());

                    //-------
                    NodeList lastNameList = firstPersonElement.getElementsByTagName("last");
                    Element lastNameElement = (Element)lastNameList.item(0);

                    NodeList textLNList = lastNameElement.getChildNodes();
                    System.out.println("Last Name : " + 
                           ((Node)textLNList.item(0)).getNodeValue().trim());

                    //----
                    NodeList ageList = firstPersonElement.getElementsByTagName("age");
                    Element ageElement = (Element)ageList.item(0);

                    NodeList textAgeList = ageElement.getChildNodes();
                    System.out.println("Age : " + 
                           ((Node)textAgeList.item(0)).getNodeValue().trim());

                    //------


                }//end of if clause


            }//end of for loop with s var


        }catch (SAXParseException err) {
        System.out.println ("** Parsing error" + ", line " 
             + err.getLineNumber () + ", uri " + err.getSystemId ());
        System.out.println(" " + err.getMessage ());

        }catch (SAXException e) {
        Exception x = e.getException ();
        ((x == null) ? e : x).printStackTrace ();

        }catch (Throwable t) {
        t.printStackTrace ();
        }
        //System.exit (0);

    }//end of main


}

结果是..

Root element of the doc is book
Total no of people : 3
First Name : Kiran
Last Name : Pai
Age : 22
First Name : Bill
Last Name : Gates
Age : 46
First Name : Steve
Last Name : Jobs
Age : 40

现在我的查询是请告知是否有其他最快的方式来阅读此 xml，我正在寻找最快的方法，请告知..!!

4

3 回答 3

26

在下面使用ReadAndPrintXMLFileWithStAX时，当我与gontard 给出ReadAndPrintXMLFileWithSAX的答案进行比较时，StAX 方法更快。我的测试涉及在 Mac 的 JDK 1.7.0_07 上运行两个示例代码时间。500000

ReadAndPrintXMLFileWithStAX:  103 seconds
ReadAndPrintXMLFileWithSAX:   125 seconds

ReadAndPrintXMLFileWithStAX（使用 Java SE 7）

下面是一个更优化的 StAX (JSR-173) 示例，使用XMLStreamReader而不是XMLEventReader.

import java.io.FileInputStream;
import java.io.InputStream;
import javax.xml.stream.*;

public class ReadAndPrintXMLFileWithStAX {

    public static void main(String argv[]) throws Exception {
        XMLInputFactory inputFactory = XMLInputFactory.newInstance();
        InputStream in = new FileInputStream("book.xml");
        XMLStreamReader streamReader = inputFactory.createXMLStreamReader(in);
        streamReader.nextTag(); // Advance to "book" element
        streamReader.nextTag(); // Advance to "person" element

        int persons = 0;
        while (streamReader.hasNext()) {
            if (streamReader.isStartElement()) {
                switch (streamReader.getLocalName()) {
                case "first": {
                    System.out.print("First Name : ");
                    System.out.println(streamReader.getElementText());
                    break;
                }
                case "last": {
                    System.out.print("Last Name : ");
                    System.out.println(streamReader.getElementText());
                    break;
                }
                case "age": {
                    System.out.print("Age : ");
                    System.out.println(streamReader.getElementText());
                    break;
                }
                case "person" : {
                    persons ++;
                }
                }
            }
            streamReader.next();
        }
        System.out.print(persons);
        System.out.println(" persons");
    }

}

输出

First Name : Kiran
Last Name : Pai
Age : 22
First Name : Bill
Last Name : Gates
Age : 46
First Name : Steve
Last Name : Jobs
Age : 40
3 persons
于 2012-09-05T01:13:33.850 回答
9

如果性能对您来说很重要，那么您应该更喜欢SAX或 StAX(http://en.wikipedia.org/wiki/StAX) 而不是DOM。

使用DOM，在第一次将XML文件解析为对象模型时，您可以询问它。因此，对于您的算法，有两遍。

随着SAX，在解析过程中，一些回调被调用（startDocument，endElement...）， SAX是基于事件或推送模型。

使用StAX，您可以控制解析。您将光标从一个元素移动到另一个元素。这是一个拉模型。

使用包含 32910000 人的文件，我将我的版本与SAX（Blaise Doughan 的）过度回答与StAX. 我删除了所有的System.out.println说明。我的程序用了 106 秒来读取所有文件，而另一个用了 94 秒。我想这SAX会更慢，因为callback即使它们什么都不做（推模型）也会调用所有的，而使用 StAX 时，光标仅在“有趣的”元素（拉模型）上移动。

以 java 7 为例：

import java.io.File;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class ReadAndPrintXMLFileWithSax {

    public static void main(String[] args) throws Exception {
        SAXParserFactory fabrique = SAXParserFactory.newInstance();
        SAXParser parser = fabrique.newSAXParser();

        File file = new File("book.xml");
        BookHandler handler = new BookHandler();
        parser.parse(file, handler);
    }

    public static class BookHandler extends DefaultHandler {
        private int count = 0;
        private StringBuilder buffer;

        @Override
        public void startElement(String uri, String localName, String qName,
                Attributes attributes) throws SAXException {
            switch (qName) {
            case "person":
                count++;
                break;
            case "first":
                buffer = new StringBuilder("First Name : ");
                break;
            case "last":
                buffer = new StringBuilder("Last Name : ");
                break;
            case "age":
                buffer = new StringBuilder("Age : ");
                break;
            }
        }

        @Override
        public void characters(char[] ch, int start, int length)
                throws SAXException {
            String content = new String(ch, start, length);
            if (buffer != null)
                buffer.append(content);
        }

        @Override
        public void endElement(String uri, String localName, String qName)
                throws SAXException {
            switch (qName) {
            case "first":
            case "last":
            case "age":
                System.out.println(buffer.toString());
                break;
            }
        }

        @Override
        public void endDocument() throws SAXException {
            System.out.println(count + " persons");
        }
    }
}
于 2012-09-04T20:56:41.260 回答
2

税务示例 

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;

public class ReadAndPrintXMLFile {


    public static void main(String argv []) {

        String inputFile = "c:/source/book.xml";

        try {
            // First create a new XMLInputFactory
            XMLInputFactory inputFactory = XMLInputFactory.newInstance();
            // Setup a new eventReader
            InputStream in = new FileInputStream(inputFile);
            XMLEventReader eventReader = inputFactory.createXMLEventReader(in);
            // Read the XML document

            while (eventReader.hasNext()) {
                XMLEvent event = eventReader.nextEvent();

                if (event.isStartElement()) {
                    StartElement startElement = event.asStartElement();

                    if (startElement.getName().getLocalPart().equals("first")) {

                        event = eventReader.nextEvent();

                        StringBuilder fName = new StringBuilder();

                        while (!event.isEndElement()) {
                            fName.append(event.asCharacters().getData());
                            event = eventReader.nextEvent();
                        }
                        System.out.println("First Name : " + fName);

                        event = eventReader.nextEvent();

                        continue;
                    }

                    if (startElement.getName().getLocalPart().equals("last")) {

                        event = eventReader.nextEvent();

                        StringBuilder lName = new StringBuilder();

                        while (!event.isEndElement()) {
                            lName.append(event.asCharacters().getData());
                            event = eventReader.nextEvent();
                        }
                        System.out.println("Last Name : " + lName);

                        event = eventReader.nextEvent();

                        continue;
                    }

                    if (startElement.getName().getLocalPart().equals("age")) {

                        event = eventReader.nextEvent();

                        StringBuilder age = new StringBuilder();

                        while (!event.isEndElement()) {
                            age.append(event.asCharacters().getData());
                            event = eventReader.nextEvent();
                        }
                        System.out.println("Age : " + age);

                        event = eventReader.nextEvent();

                        continue;
                    }

                }
            }
        } catch (FileNotFoundException e) {
            System.out.println("File not Found: " + inputFile);
        } catch (XMLStreamException e) {
            e.printStackTrace();
        }
    }

}


输出： 

First Name : Kiran
Last Name : Pai
Age : 22
First Name : Bill
Last Name : Gates
Age : 46
First Name : Steve
Last Name : Jobs
Age : 40
于 2012-09-04T19:50:55.480 回答