XML是一种通用的数据交换花样,它的平台无关性、言语无关性、体系无关性、给数据集成与交互带来了极大的轻易。接下来将要在文章中为人人细致引见在Java中剖析XML的体式格局，具有肯定的参考作用，愿望对人人有所协助
【引荐课程：XML教程】
运用DOM剖析
DOM剖析器重要用于在内存中运用XML作为对象图（树状构造） 也就是文档对象模子（DOM）。起首剖析器遍历输入XML文件并建立与XML文件中的节点相对应的DOM对象。这些DOM对象以树状构造链接在一起。一旦剖析器完成了剖析历程，就会从中取得这个相似树的DOM对象构造。
例：在所有代码示例中剖析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;
}
}
输出效果为：
Rakesh Mishra(111)Bangalore John Davis(112)Chennai Rajesh Sharma(113)Pune
运用SAX 剖析
SAX Parser与DOM剖析器的差别之处在于SAX剖析器不会将完全的XML加载到内存中，而是在碰到差别的元素时，它逐行剖析XML，c触发差别的事宜，比方：翻开标记，完毕标记，字符数据，批评等。
运用SAX Parser剖析XML的代码以下：
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;
}
}
输出效果为：
Rakesh Mishra(111)Bangalore John Davis(112)Chennai Rajesh Sharma(113)Pune
运用StAX Parser
StAX用于XML的Streaming API，而StAX Parser与SA的差别之处在于SAX Parser。StAX剖析器也是一种与SAX剖析器也是有所差别的
SAX Parser会推送数据，但StAX剖析器会从XML中提取所需的数据。StAX剖析器将光标维持在文档中的当前位置，许可提取光标处可用的内容，而SAX剖析器在碰到某些数据时发出事宜。
XMLInputFactory和XMLStreamReader是可用于加载XML文件的两个类。当我们运用XMLStreamReader读取XML文件时，事宜以整数值的情势生成，然后将这些事宜与XMLStreamConstants中的常量举行比较。以下代码显现了怎样运用StAX剖析器剖析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;
}
}
输出效果为：
Rakesh Mishra(111) Bangalore John Davis(112) Chennai Rajesh Sharma(113) Pune
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