读取XML文件

   JAVA操作XML文档主要有四种方式，分别是DOM、SAX、JDOM和DOM4J，DOM和SAX是官方提供的，而JDOM和DOM4J则是引用第三方库的，其中用的最多的是DOM4J方式。运行效率和内存使用方面最优的是SAX，但是由于SAX是基于事件的方式，所以SAX无法在编写XML的过程中对已编写内容进行修改，但对于不用进行频繁修改的需求，还是应该选择使用SAX。

   下面基于这四种方式来读取XML文件。

 

   第一，以DOM的方式实现。

 1 package xmls; 2 import org.w3c.dom.Document; 3 import org.w3c.dom.Element; 4 import org.w3c.dom.Node; 5 import org.w3c.dom.NodeList; 6 import org.xml.sax.SAXException; 7 import javax.xml.parsers.DocumentBuilder; 8 import javax.xml.parsers.DocumentBuilderFactory; 9 import javax.xml.parsers.ParserConfigurationException;10 import java.io.File;11 import java.io.IOException;12 /**13  * Created by lenovo on 2017-6-3.14  */15 public class DOMReadDemo {16     public static void main(String[] args){17         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();18         try{19             DocumentBuilder db = dbf.newDocumentBuilder();20             Document document = db.parse("src/xmls/DOM.xml");21             NodeList booklist = document.getElementsByTagName("book");22             for(int i = 0; i < booklist.getLength(); i++){23                 System.out.println("--------第" + (i+1) + "本书----------");24                 Element ele = (Element) booklist.item(i);25                 NodeList childNodes= ele.getChildNodes();26                 for(int j = 0; j < childNodes.getLength(); j++){27                     Node n = childNodes.item(j);28                     if(n.getNodeName() != "#text"){29                         System.out.println(n.getNodeName() + ":" + n.getTextContent());30                     }31                 }32                 System.out.println("---------------------------------");33             }34         }catch (ParserConfigurationException e){35             e.printStackTrace();36         }catch (IOException e){37             e.printStackTrace();38         }catch (SAXException e){39             e.printStackTrace();40         }41     }42 }

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第二，以SAX的方式实现。

 1 package xmls; 2 import javax.xml.parsers.SAXParser; 3 import javax.xml.parsers.SAXParserFactory; 4 /** 5  * Created by lenovo on 2017-6-1. 6  */ 7 public class xmlTest2 { 8     public static void main(String[] args){ 9         SAXParserFactory spf = SAXParserFactory.newInstance();10         try{11             SAXParser sp = spf.newSAXParser();12             SAXParserHandler handler = new SAXParserHandler();13             sp.parse("src\\xmls\\book.xml", handler);14         }catch (Exception e){15             e.printStackTrace();16         }17     }18 }

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 1 package xmls; 2 import org.xml.sax.Attributes; 3 import org.xml.sax.SAXException; 4 import org.xml.sax.helpers.DefaultHandler; 5 /** 6  * Created by lenovo on 2017-6-1. 7  */ 8 public class SAXParserHandler extends DefaultHandler { 9     @Override10     public void startDocument() throws SAXException {11         super.startDocument();12         System.out.println("SAX解析开始");13     }14     @Override15     public void endDocument() throws SAXException {16         super.endDocument();17         System.out.println("SAX解析结束");18     }19     @Override20     public void startElement(String s, String s1, String s2, Attributes attributes) throws SAXException {21         super.startElement(s, s1, s2, attributes);22         System.out.println(s2);23         for(int i = 0; i < attributes.getLength(); i++){24             String name = attributes.getQName(i);25             String value = attributes.getValue(name);26             System.out.println("属性值：" + name + "=" + value);27         }28     }29     @Override30     public void endElement(String s, String s1, String s2) throws SAXException {31         super.endElement(s, s1, s2);32         if(s2.equals("book")){33             System.out.println("-----------------------");34         }35     }36     @Override37     public void characters(char[] ch, int start, int length) throws SAXException {38         super.characters(ch, start, length);39         String value = new String(ch, start, length);40         if(value.trim().equals("")){41             return;42         }43         System.out.println(value);44     }45 }

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第三，以JDOM的方式实现。

 1 package xmls; 2 import org.jdom2.Attribute; 3 import org.jdom2.Document; 4 import org.jdom2.Element; 5 import org.jdom2.JDOMException; 6 import org.jdom2.input.JDOMParseException; 7 import org.jdom2.input.SAXBuilder; 8 import java.io.*; 9 import java.util.List;10 /**11  * Created by lenovo on 2017-6-2.12  */13 public class JDOMTest {14     public static void main(String[] args){15         SAXBuilder saxBuilder = new SAXBuilder();16         InputStream in;17         try{18             in = new FileInputStream(new File("src\\xmls\\book.xml"));19             Document document = saxBuilder.build(in);20             Element rootElement = document.getRootElement();21             List<Element> bookList = rootElement.getChildren();22             for(Element book: bookList){23                 System.out.println("第" + (bookList.indexOf(book)+1) + "本书！");24                 List<Attribute> attrs = book.getAttributes();25                 for(Attribute attr: attrs){26                     System.out.println(attr.getName() + "=" + attr.getValue());27                 }28                 for(Element item: book.getChildren()){29                     System.out.println(item.getName() + ":" + item.getValue());30                 }31                 System.out.println("------------------------------------");32             }33         }catch (FileNotFoundException e){34             e.printStackTrace();35         }catch (JDOMException e){36             e.printStackTrace();37         }catch (IOException e){38             e.printStackTrace();39         }40     }41 }

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    第四，以DOM4J的方式实现。

 1 package xmls; 2 import org.dom4j.*; 3 import org.dom4j.io.OutputFormat; 4 import org.dom4j.io.SAXReader; 5 import org.dom4j.io.XMLWriter; 6 import java.io.File; 7 import java.io.FileOutputStream; 8 import java.io.IOException; 9 import java.util.Iterator;10 import java.util.List;11 /**12  * Created by lenovo on 2017-6-2.13  */14 public class DOM4JTest {15     public void parseXML(){16         SAXReader saxReader = new SAXReader();17         try{18             Document document = saxReader.read(new File("src\\xmls\\book.xml"));19             Element rootElement = document.getRootElement();20             Iterator it = rootElement.elementIterator();21             while (it.hasNext()){22                 Element book = (Element)it.next();23                 List<Attribute> attrs = book.attributes();24                 for(Attribute attr: attrs){25                     System.out.println("属性名：" + attr.getName() + "---- 属性值：" + attr.getValue() );26                 }27                 Iterator cit = book.elementIterator();28                 while (cit.hasNext()){29                     Element child = (Element) cit.next();30                     System.out.println("子节点：" + child.getName());31                 }32             }33         }catch (DocumentException e){34             e.printStackTrace();35         }36     }37     public static void main(String[] args){38         DOM4JTest dom4JTest = new DOM4JTest();39         dom4JTest.parseXML();40     }41 }

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