Java中解析XML的方式有哪些

java解析XML的方式有使用DOM解析通过DOM对象以树状结构连接在一起；使用SAX 解析它是遇到不同元素时会逐行解析；使用StAX解析会从XML中提取所需的数据

XML是一种通用的数据交换格式,它的平台无关性、语言无关性、系统无关性、给数据集成与交互带来了极大的方便。接下来将要在文章中为大家具体介绍在Java中解析XML的方式，具有一定的参考作用，希望对大家有所帮助

【推荐课程：XML教程】

使用DOM解析

DOM解析器主要用于在内存中使用XML作为对象图（树状结构）也就是文档对象模型（DOM）。首先解析器遍历输入XML文件并创建与XML文件中的节点相对应的DOM对象。这些DOM对象以树状结构链接在一起。一旦解析器完成了解析过程，就会从中获得这个类似树的DOM对象结构。

例：在所有代码示例中解析xml内容

public class DOMParserDemo {   public static void main(String[] args) throws Exception {    DocumentBuilderFactory factory =        DocumentBuilderFactory.newInstance();    DocumentBuilder builder = factory.newDocumentBuilder();    Document document =      builder.parse(        ClassLoader.getSystemResourceAsStream("xml/employee.xml"));    List<Employee> empList = new ArrayList<>();    NodeList nodeList = document.getDocumentElement().getChildNodes();    for (int i = 0; i < nodeList.getLength(); i++) {      Node node = nodeList.item(i);      if (node instanceof Element) {        Employee emp = new Employee();        emp.id = node.getAttributes().            getNamedItem("id").getNodeValue();        NodeList childNodes = node.getChildNodes();        for (int j = 0; j < childNodes.getLength(); j++) {          Node cNode = childNodes.item(j);          if (cNode instanceof Element) {            String content = cNode.getLastChild().                getTextContent().trim();            switch (cNode.getNodeName()) {              case "firstName":                emp.firstName = content;                break;              case "lastName":                emp.lastName = content;                break;              case "location":                emp.location = content;                break;            }          }        }        empList.add(emp);      }    }       for (Employee emp : empList) {      System.out.println(emp);    }   }}class Employee{  String id;  String firstName;  String lastName;  String location;   @Override  public String toString() {    return firstName+" "+lastName+"("+id+")"+location;  }}

输出结果为：

Rakesh Mishra(111)BangaloreJohn Davis(112)ChennaiRajesh Sharma(113)Pune

使用SAX 解析

SAX Parser与DOM解析器的不同之处在于SAX解析器不会将完整的XML加载到内存中，而是在遇到不同的元素时，它逐行解析XML，c触发不同的事件，例如：打开标记，结束标记，字符数据，评论等。

使用SAX Parser解析XML的代码如下：

import java.util.ArrayList;import java.util.List;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;public class SAXParserDemo {  public static void main(String[] args) throws Exception {    SAXParserFactory parserFactor = SAXParserFactory.newInstance();    SAXParser parser = parserFactor.newSAXParser();    SAXHandler handler = new SAXHandler();    parser.parse(ClassLoader.getSystemResourceAsStream("xml/employee.xml"),                 handler);    for ( Employee emp : handler.empList){      System.out.println(emp);    }  }}class SAXHandler extends DefaultHandler {   List<Employee> empList = new ArrayList<>();  Employee emp = null;  String content = null;  @Override  public void startElement(String uri, String localName,                           String qName, Attributes attributes)                           throws SAXException {           switch(qName){      case "employee":        emp = new Employee();        emp.id = attributes.getValue("id");        break;    }  }   @Override  public void endElement(String uri, String localName,                         String qName) throws SAXException {   switch(qName){     case "employee":       empList.add(emp);             break;     case "firstName":       emp.firstName = content;       break;     case "lastName":       emp.lastName = content;       break;     case "location":       emp.location = content;       break;   }  }   @Override  public void characters(char[] ch, int start, int length)          throws SAXException {    content = String.copyValueOf(ch, start, length).trim();  }     } class Employee {  String id;  String firstName;  String lastName;  String location;   @Override  public String toString() {    return firstName + " " + lastName + "(" + id + ")" + location;  }}

输出结果为：

Rakesh Mishra(111)BangaloreJohn Davis(112)ChennaiRajesh Sharma(113)Pune

使用StAX Parser

StAX用于XML的Streaming API，而StAX Parser与SA的不同之处在于SAX Parser。StAX解析器也是一种与SAX解析器也是有所不同的

SAX Parser会推送数据，但StAX解析器会从XML中提取所需的数据。StAX解析器将光标维持在文档中的当前位置，允许提取光标处可用的内容，而SAX解析器在遇到某些数据时发出事件。

XMLInputFactory和XMLStreamReader是可用于加载XML文件的两个类。当我们使用XMLStreamReader读取XML文件时，事件以整数值的形式生成，然后将这些事件与XMLStreamConstants中的常量进行比较。以下代码显示了如何使用StAX解析器解析XML：

import java.util.ArrayList;import java.util.List;import javax.xml.stream.XMLInputFactory;import javax.xml.stream.XMLStreamConstants;import javax.xml.stream.XMLStreamException;import javax.xml.stream.XMLStreamReader; public class StaxParserDemo {  public static void main(String[] args) throws XMLStreamException {    List<Employee> empList = null;    Employee currEmp = null;    String tagContent = null;    XMLInputFactory factory = XMLInputFactory.newInstance();    XMLStreamReader reader =        factory.createXMLStreamReader(        ClassLoader.getSystemResourceAsStream("xml/employee.xml"));             while(reader.hasNext()){      int event = reader.next();      switch(event){        case XMLStreamConstants.START_ELEMENT:          if ("employee".equals(reader.getLocalName())){            currEmp = new Employee();            currEmp.id = reader.getAttributeValue(0);          }          if("employees".equals(reader.getLocalName())){            empList = new ArrayList<>();          }          break;                   case XMLStreamConstants.CHARACTERS:          tagContent = reader.getText().trim();          break;                   case XMLStreamConstants.END_ELEMENT:          switch(reader.getLocalName()){            case "employee":              empList.add(currEmp);              break;            case "firstName":              currEmp.firstName = tagContent;              break;            case "lastName":              currEmp.lastName = tagContent;              break;            case "location":              currEmp.location = tagContent;              break;          }          break;        case XMLStreamConstants.START_DOCUMENT:          empList = new ArrayList<>();          break;      }     }    for ( Employee emp : empList){      System.out.println(emp);    }         }} class Employee{  String id;  String firstName;  String lastName;  String location;     @Override  public String toString(){    return firstName+" "+lastName+"("+id+") "+location;  }}

输出结果为：

Rakesh Mishra(111) BangaloreJohn Davis(112) ChennaiRajesh Sharma(113) Pune

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