dom4j解析和生成XML文件

转化XML

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.io.SAXReader;

public class Foo {

    public Document parse(URL url) throws DocumentException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(url);
        return document;
    }
}

使用迭代器

document可以通过几个返回Java标准迭代器的方法实现遍历：

public void bar(Document document) throws DocumentException {

    Element root = document.getRootElement();

    // iterate through child elements of root
    for ( Iterator i = root.elementIterator(); i.hasNext(); ) {
        Element element = (Element) i.next();
        // do something
    }

    // iterate through child elements of root with element name "foo"
    for ( Iterator i = root.elementIterator( "foo" ); i.hasNext(); ) {
        Element foo = (Element) i.next();
        // do something
    }

    // iterate through attributes of root 
    for ( Iterator i = root.attributeIterator(); i.hasNext(); ) {
        Attribute attribute = (Attribute) i.next();
        // do something
    }
 }

快速循环

快速遍历大文件：

public void treeWalk(Document document) {
     treeWalk( document.getRootElement() );
 }

 public void treeWalk(Element element) {
     for ( int i = 0, size = element.nodeCount(); i < size; i++ ) {
         Node node = element.node(i);
         if ( node instanceof Element ) {
             treeWalk( (Element) node );
         }
         else {
             // do something....
         }
     }
 }

创建XML文档

import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;

public class Foo {

    public Document createDocument() {
        Document document = DocumentHelper.createDocument();
        Element root = document.addElement( "root" );

        Element author1 = root.addElement( "author" )
            .addAttribute( "name", "James" )
            .addAttribute( "location", "UK" )
            .addText( "James Strachan" );

        Element author2 = root.addElement( "author" )
            .addAttribute( "name", "Bob" )
            .addAttribute( "location", "US" )
            .addText( "Bob McWhirter" );

        return document;
    }
}

将文档写入文件

一种快速而且简单的方式如下：

FileWriter out = new FileWriter( "foo.xml" );
document.write( out );

如果想要修改输出的格式，如智能缩进输出或者紧凑输出，或者你想要使用writer对象或者OutputStream对象来完成其他任务，则可以使用XMLWriter类。

import org.dom4j.Document;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;

public class Foo {

    public void write(Document document) throws IOException {

        // lets write to a file
        XMLWriter writer = new XMLWriter(
            new FileWriter( "output.xml" )
        );
        writer.write( document );
        writer.close();


        // Pretty print the document to System.out
        OutputFormat format = OutputFormat.createPrettyPrint();
        writer = new XMLWriter( System.out, format );
        writer.write( document );

        // Compact format to System.out
        format = OutputFormat.createCompactFormat();
        writer = new XMLWriter( System.out, format );
        writer.write( document );
    }
}

与String的转化

如果有到Document或者其他结点如Attribute、Element等的引用，则可以用asXML()方法将其转化为默认的XML文本。

Document document = ...;
String text = document.asXML();

如果有String形式的XML，则可以使用DocumentHelper.parseText()将其转化为Document。

String text = "<person> <name>James</name> </person>";
Document document = DocumentHelper.parseText(text);

其他操作

1 取得某结点下的某个子节点或属性

Element root = document.getRootElement();
Element elem = root.element("book");
Attribute attribute = root.attribute("id");

2 取得属性的内容

String text = attribute.getText();

3 删除某属性

Attribute attribute=root.attribute("id"); 
root.remove(attribute);

一个完整的解析和生成XML文件示例

package test;

import java.io.*;
import java.util.Iterator;
import java.util.List;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import org.dom4j.Attribute;

class XMLHelper {
    /** * 解析XML * @param filename 要解析的XML的文件名 */
    public static void resolveXML(String filename) {
        try {
            SAXReader reader = new SAXReader();
            Document document = reader.read(new File(filename));
            Element root = document.getRootElement();
            System.out.println("Root: " + root.getName());
            for (Iterator it = root.elementIterator(); it.hasNext(); ) {
                Element e = (Element)it.next();
                System.out.print(e.getName());
                //遍历属性
                for (Iterator it1 = e.attributeIterator(); it1.hasNext(); ) {
                    Attribute attribute = (Attribute)it1.next();
                    System.out.println("[" + attribute.getName() + ": " +
                        attribute.getText() + "]");
                }
                //遍历子节点
                for (Iterator it2 = e.elementIterator(); it2.hasNext(); ) {
                    Element ee = (Element)it2.next();
                    System.out.println(" " + ee.getName() + ": " + 
                        ee.getText() + " ");
                }
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public static Document createDocument() {
        Document document = DocumentHelper.createDocument();
        Element root = document.addElement("bookstore");
        //add book
        Element book = root.addElement("book")
            .addAttribute("category", "COOKING");
        book.addElement("title")
            .addText("Everyday Italian");
        book.addElement("author")
            .addText("Giada De Laurentiis");
        book.addElement("year")
            .addText("2005");
        book.addElement("price")
            .addText("30.00");
        //add book
        book = root.addElement("book")
            .addAttribute("category", "CHILDREN");
        book.addElement("title")
            .addText("Harry Potter");
        book.addElement("author")
            .addText("J K. Rowling");
        book.addElement("year")
            .addText("2005");
        book.addElement("price")
            .addText("29.99");

        return document;
    }

    /** * 生成XML文件 * @param filename 将生成的XML输出到该文件 */
    public static void write(String filename) {
        Document document = createDocument(); 
        try {
            //write to a file
            OutputFormat f=OutputFormat.createPrettyPrint();
            XMLWriter writer = new XMLWriter(new FileWriter(filename), f);
            writer.write(document);
            writer.close();

            //Pretty print the document to System.out
            /*OutputFormat format = OutputFormat.createPrettyPrint(); writer = new XMLWriter(System.out, format); writer.write(document);*/

            //Compact print the document to System.out
            /*format = OutputFormat.createCompactFormat(); writer = new XMLWriter(System.out, format); writer.write(document);*/
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

public class Main {
    public static void main(String[] args) throws Exception{
        String filename = "E:\\Eclipse Project\\WebTest\\WebContent\\myxml.xml";
        XMLHelper.resolveXML(filename);
        filename = "E:\\Eclipse Project\\WebTest\\WebContent\\myxml2.xml";
        XMLHelper.write(filename);
    }
}