java中采用dom4j解析xml文件

一.前言

在最近的开发中用到了dom4j来解析xml文件，以前听说过来解析xml文件的几种标准方式；但是从来的没有应用过来，所以可以在google中搜索dmo4j解析xml文件的方式，学习一下dom4j解析xml的具体操作。

二.代码详情

   dom4j是一个第三方开发组开发出的插件，所以在我们使用dom4jf的时候我们要去下载一下dom4j对应版本的jar导入在我们项目中。

 1)xml文件:

<?xml version="1.0" encoding="UTF-8"?>
<books>
   <book id="001">
      <title>Harry Potter</title>
      <author>J K. Rowling</author>
   </book>
   <book id="002">
      <title>Learning XML</title>
      <author>Erik T. Ray</author>
   </book>
</books> 

示例一：用List列表的方式来解析xml

SAXReader就是一个管道，用一个流的方式，把xml文件读出来

import java.io.File;
import java.util.List;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class Demo {

    public static void main(String[] args) throws Exception {
        SAXReader reader = new SAXReader();
        File file = new File("books.xml");
        Document document = reader.read(file);
        Element root = document.getRootElement();
        List<Element> childElements = root.elements();
        for (Element child : childElements) {
            //未知属性名情况下
            /*List<Attribute> attributeList = child.attributes();
            for (Attribute attr : attributeList) {
                System.out.println(attr.getName() + ": " + attr.getValue());
            }*/

            //已知属性名情况下
            System.out.println("id: " + child.attributeValue("id"));

            //未知子元素名情况下
            /*List<Element> elementList = child.elements();
            for (Element ele : elementList) {
                System.out.println(ele.getName() + ": " + ele.getText());
            }
            System.out.println();*/

            //已知子元素名的情况下
            System.out.println("title" + child.elementText("title"));
            System.out.println("author" + child.elementText("author"));
            //这行是为了格式化美观而存在
            System.out.println();
        }
    }

}

示例二：使用Iterator迭代器的方式来解析xml

import java.io.File;
import java.util.Iterator;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class Demo {
    public static void main(String[] args) throws Exception {
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("books.xml"));
        Element root = document.getRootElement();

        Iterator it = root.elementIterator();
        while (it.hasNext()) {
            Element element = (Element) it.next();

            //未知属性名称情况下
            /*Iterator attrIt = element.attributeIterator();
            while (attrIt.hasNext()) {
                Attribute a  = (Attribute) attrIt.next();
                System.out.println(a.getValue());
            }*/

            //已知属性名称情况下
            System.out.println("id: " + element.attributeValue("id"));

            //未知元素名情况下
            /*Iterator eleIt = element.elementIterator();
            while (eleIt.hasNext()) {
                Element e = (Element) eleIt.next();
                System.out.println(e.getName() + ": " + e.getText());
            }
            System.out.println();*/

            //已知元素名情况下
            System.out.println("title: " + element.elementText("title"));
            System.out.println("author: " + element.elementText("author"));
            System.out.println();
        }
    }
}

运行结果：

示例三：创建xml文档并输出到文件

import java.io.File;
import java.io.FileOutputStream;

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

public class Demo {
    public static void main(String[] args) throws Exception {
        Document doc = DocumentHelper.createDocument();
        //增加根节点
        Element books = doc.addElement("books");
        //增加子元素
        Element book1 = books.addElement("book");
        Element title1 = book1.addElement("title");
        Element author1 = book1.addElement("author");

        Element book2 = books.addElement("book");
        Element title2 = book2.addElement("title");
        Element author2 = book2.addElement("author");

        //为子节点添加属性
        book1.addAttribute("id", "001");
        //为元素添加内容
        title1.setText("Harry Potter");
        author1.setText("J K. Rowling");

        book2.addAttribute("id", "002");
        title2.setText("Learning XML");
        author2.setText("Erik T. Ray");

        //实例化输出格式对象
        OutputFormat format = OutputFormat.createPrettyPrint();
        //设置输出编码
        format.setEncoding("UTF-8");
        //创建需要写入的File对象
        File file = new File("D:" + File.separator + "books.xml");
        //生成XMLWriter对象，构造函数中的参数为需要输出的文件流和格式
        XMLWriter writer = new XMLWriter(new FileOutputStream(file), format);
        //开始写入，write方法中包含上面创建的Document对象
        writer.write(doc);
    }
}

运行结果：