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
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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)Bangalore John Davis(112)Chennai Rajesh 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)Bangalore John Davis(112)Chennai Rajesh 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) Bangalore John Davis(112) Chennai Rajesh Sharma(113) Pune
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