解析XML文件的几种常见操作方法：DOM/SAX/DOM4j

<?xml version="1.0" encoding="utf-8"?>
<root>
    <class name="class1">
        <student>
            <name>张三</name>
            <age>20</age>
            <sex>男</sex>
        </student>
        <student>
            <name>Andy</name>
            <age>22</age>
            <sex>female</sex>
        </student>
    </class>
    <class name="class2">
        <student>
            <name>李四</name>
            <age>15</age>
            <sex>男</sex>
        </student>
        <student>
            <name>bigbang</name>
            <age>21</age>
            <sex>女</sex>
        </student>
    </class>
</root>

1. DOM解析是一种消耗内存的解析方法，它先将整个xml文档装入内存，然后顺序读取，解析有些复杂。

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import com.entity.Student;

public class DOMParse {

    private Student student;
    private List<Student> students;

    public void pasre() {
        students = new ArrayList<Student>();
        try {
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = dbf.newDocumentBuilder();
            // 在此没有使用InputStream作为参数，直接引用文件路径。
            Document doc = builder.parse("src/com/parseDom/test.xml");
            // 获取整个document元素
            Element element = doc.getDocumentElement();
            // 获取所有<class>子节点
            NodeList list = element.getElementsByTagName("class"); // <class>
            // 遍历class子节点
            for (int i = 0; i < list.getLength(); i++) {
                Element el = (Element) list.item(i);
                // 获取<student>节点
                NodeList stus = el.getElementsByTagName("student"); // <student>
                // 遍历student子节点
                for (int j = 0; j < stus.getLength(); j++) {
                    /**
                     * 获取student下所有子节点 此处有7个节点，分别是#text<name> #text<sex>
                     * #text<age> #text
                     * 对应的xml实际是<student>、<name>、#name、<sex>、#sex
                     * 、<age>、#age这七个子节点
                     * **/
                    NodeList lis = stus.item(j).getChildNodes();
                    // 每个student节点输出就是一个Student对象
                    student = new Student();
                    for (int k = 0; k < lis.getLength(); k++) {
                        // 当元素为节点元素时（非textValue），对比后取值
                        if (lis.item(k).getNodeType() == Node.ELEMENT_NODE) {
                            if ("name".equals(lis.item(k).getNodeName())) { // <name>
                                student.setName(lis.item(k).getFirstChild().getNodeValue());
                            }
                            if ("sex".equals(lis.item(k).getNodeName())) { // <sex>
                                student.setSex(lis.item(k).getFirstChild().getNodeValue());
                            }
                            if ("age".equals(lis.item(k).getNodeName())) { // <age>
                                student.setAge(Integer.parseInt(lis.item(k).getFirstChild().getNodeValue()));
                            }
                        }
                    }
                    students.add(student);
                }
            }

        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            for (Student stus : students) {
                System.out.println(stus.getName() + "--" + stus.getSex() + "--" + stus.getAge());
            }
        }
    }

    public static void main(String[] args) {
        DOMParse domParse = new DOMParse();
        domParse.pasre();
    }
}

2.SAX解析方法如下。

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.ParserConfigurationException;
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;

import com.entity.Student;

public class SAXParse extends DefaultHandler{

    
    private Student student;
    private static List<Student> stus;
    private String preTag=null;

    //①程序启动执行
    @Override
    public void startDocument() throws SAXException {
            stus = new ArrayList<Student>();
    }
    
    //② 开始遍历元素时
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        if("student".equals(qName)){
            student = new Student();
//            student.setName(attributes.getValue(0));
        }
        preTag = qName;
    }

    //④元素遍历结束
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if("student".equals(qName)){
            stus.add(student);
            student = null;
        }
        preTag=null;
    }

    //③ 遍历取值过程
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        if(preTag!=null){
            String content = new String(ch,start,length);
            if("name".equals(preTag)){
                student.setName(content);
            }
            if("age".equals(preTag)){
                student.setAge(Integer.parseInt(content));
            }
            if("sex".equals(preTag)){
                student.setSex(content);
            }
        }
    }

    public void fun(){
        try {
            SAXParserFactory factory =SAXParserFactory.newInstance();
            SAXParser    parser = factory.newSAXParser();
            SAXParse handler = new SAXParse();
            parser.parse("src/com/parseDom/test.xml", handler);
        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static  List<Student> getStus(){
        return stus;
    }
    
    public static void main(String[] args) {
        new SAXParse().fun();
        for (Student stu : getStus()) {
            System.out.println(stu.getName()+"--"+stu.getAge()+"--"+stu.getSex());
        }
    }
}

3.DOM4J的解析方法如下，需要注意的是它的Document类和Element类是DOM4J的jar包提供的，不要引用错了。

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

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

import com.entity.Student;

public class DOM4J {

    private Student student;
    private List<Student> stus;
    
    @SuppressWarnings("unchecked")
    public void parse(){
        stus = new ArrayList<Student>();
        try {
            SAXReader reader = new SAXReader();
            
            //此处Document类和Element类均为DOM4j的jar包中的类
            Document doc =  reader.read("src/com/parseDom/test.xml");
            //获取根元素
            Element root = doc.getRootElement();
            //获取节点元素为"class"的迭代
            Iterator<Element> classss = root.elementIterator("class");
            while(classss.hasNext()){
                Element classs =classss.next();
                //获取节点元素为"student"的迭代
                Iterator<Element> students = classs.elementIterator("student");
                while (students.hasNext()) {
                    //每一个student节点元素都包括一个student对象
                    student = new Student();
                    Element els = students.next();
                    //根据节点元素取值
                    student.setName(els.elementText("name"));
                    student.setAge(Integer.parseInt(els.elementText("age")));
                    student.setSex(els.elementText("sex"));
                    stus.add(student);
                }
            }
        } catch (DocumentException e) {
            e.printStackTrace();
        } finally{
            for (Student stu : stus) {
                System.out.println(stu.getName()+"++"+stu.getSex()+"++"+stu.getAge());
            }
        }
    }
    
    
    public static void main(String[] args) {
        new DOM4J().parse();
    }
}

最后的输出结果是：

张三++男++20
Andy++female++22
李四++男++15
bigbang++女++21