java解析XML的方式有使用DOM解析透過DOM物件以樹狀結構連接在一起；使用SAX 解析它是遇到不同元素時會逐行解析；使用StAX解析會從XML中提取所需的資料
XML是一種通用的資料交換格式,它的平台無關性、語言無關性、系統無關性、給資料整合與互動帶來了極大的方便。接下來將會在文章中為大家具體介紹在Java中解析XML的方式，具有一定的參考作用，希望對大家有所幫助
##【推薦課程：XML教學】
#使用DOM解析##DOM解析器主要用於在記憶體中使用XML作為物件圖（樹狀結構） 也就是文件物件模型（DOM）。首先解析器遍歷輸入XML檔案並建立與XML檔案中的節點相對應的DOM物件。這些DOM物件以樹狀結構連結在一起。一旦解析器完成了解析過程，就會從中得到這個類似樹的DOM物件結構。
範例：在所有程式碼範例中解析xml內容
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;
}
}Rakesh Mishra(111)Bangalore John Davis(112)Chennai Rajesh Sharma(113)Pune
SAX Parser與DOM解析器的不同之處在於SAX解析器不會將完整的XML載入到記憶體中，而是在遇到不同的元素時，它逐行解析XML，c觸發不同的事件，例如：開啟標記，結束標記，字元數據，評論等。
使用SAX Parser解析XML的程式碼如下：
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;
}
}Rakesh Mishra(111)Bangalore
John Davis(112)Chennai
Rajesh Sharma(113)Pune
#StAX用於XML的Streaming API，而StAX Parser與SA的不同之處在於SAX Parser。 StAX解析器也是一種與SAX解析器也是有所不同的
SAX Parser會推送數據，但StAX解析器會從XML中提取所需的數據。 StAX解析器將遊標維持在文件中的目前位置，允許提取遊標處可用的內容，而SAX解析器在遇到某些資料時發出事件。
XMLInputFactory和XMLStreamReader是兩個可用來載入XML檔案的類別。當我們使用XMLStreamReader讀取XML檔案時，事件會以整數值的形式生成，然後將這些事件與XMLStreamConstants中的常數進行比較。以下程式碼顯示如何使用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;
}
}Rakesh Mishra(111) Bangalore John Davis(112) Chennai Rajesh Sharma(113) Pune
以上是Java中解析XML的方式有哪些的詳細內容。更多資訊請關注PHP中文網其他相關文章！
