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