3) StAX 游标 API 示例
package com.onitroad.demo.stax;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.List;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
public class ReadXMLExample
{
public static void main(String[] args) throws FileNotFoundException, XMLStreamException
{
//All read employees objects will be added to this list
List<Employee> employeeList = new ArrayList<>();
//Create Employee object. It will get all the data using setter methods.
//And at last, it will stored in above 'employeeList'
Employee employee = null;
File file = new File("employees.xml");
XMLInputFactory factory = XMLInputFactory.newInstance();
XMLStreamReader streamReader = factory.createXMLStreamReader(new FileReader(file));
while(streamReader.hasNext())
{
//Move to next event
streamReader.next();
//Check if its 'START_ELEMENT'
if(streamReader.getEventType() == XMLStreamReader.START_ELEMENT)
{
//employee tag - opened
if(streamReader.getLocalName().equalsIgnoreCase("employee")) {
//Create new employee object asap tag is open
employee = new Employee();
//Read attributes within employee tag
if(streamReader.getAttributeCount() > 0) {
String id = streamReader.getAttributeValue(null,"id");
employee.setId(Integer.valueOf(id));
}
}
//Read name data
if(streamReader.getLocalName().equalsIgnoreCase("name")) {
employee.setName(streamReader.getElementText());
}
//Read title data
if(streamReader.getLocalName().equalsIgnoreCase("title")) {
employee.setTitle(streamReader.getElementText());
}
}
//If employee tag is closed then add the employee object to list
if(streamReader.getEventType() == XMLStreamReader.END_ELEMENT)
{
if(streamReader.getLocalName().equalsIgnoreCase("employee")) {
employeeList.add(employee);
}
}
}
//Verify read data
System.out.println(employeeList);
}
}
1) StAX 解析器
就像 SAX 解析器一样，StAX API 是为解析 XML 流而设计的。
区别在于：
- StAX 是一个“拉取”API。SAX 是一个“推送”API。
- StAX 可以进行 XML 读取和写入。SAX 只能做 XML 读取。
StAX 是一个拉取式 API。
这意味着我们必须自己将 StAX 解析器从 XML 文件中的一项移到另一项，就像使用标准的 Iterator或者 JDBC ResultSet一样。
然后，我们可以通过 StAX 解析器访问 XML 文件中遇到的每个此类“项目”的 XML 信息。
游标与迭代器
- 在读取 XML 文档时，迭代器读取器从它的
nextEvent()调用返回一个 XML 事件对象。此事件提供有关我们遇到的 XML 标记类型（元素、文本、注释等）的信息。接收到的事件是不可变的，因此我们可以传递应用程序以安全地处理它。
XMLEventReader reader = ...;
while(reader.hasNext()){
XMLEvent event = reader.nextEvent();
if(event.getEventType() == XMLEvent.START_ELEMENT){
//process data
}
//... more event types handled here...
}
- 与迭代器不同，游标的工作方式类似于 JDBC 中的“结果集”。如果将光标移动到 XML 文档中的下一个元素。然后，我们可以直接在光标上调用方法以获取有关当前事件的更多信息。
XMLStreamReader streamReader = ...;
while(streamReader.hasNext()){
int eventType = streamReader.next();
if(eventType == XMLStreamReader.START_ELEMENT){
System.out.println(streamReader.getLocalName());
}
//... more event types handled here...
}
on it road.com
2) StAX 迭代器 API 示例
下面演示了如何使用基于 StAX 迭代器的 API 来读取 XML 文档到对象。
测试 XML文件
<employees> <employee id="101"> <name>JackLi Gupta</name> <title>Author</title> </employee> <employee id="102"> <name>BobRobert Lara</name> <title>Cricketer</title> </employee> </employees>
使用 StAX Iterator 读取 XML
package com.onitroad.demo.stax;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.xml.namespace.QName;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
public class ReadXMLExample
{
public static void main(String[] args) throws FileNotFoundException, XMLStreamException
{
File file = new File("employees.xml");
// Instance of the class which helps on reading tags
XMLInputFactory factory = XMLInputFactory.newInstance();
// Initializing the handler to access the tags in the XML file
XMLEventReader eventReader = factory.createXMLEventReader(new FileReader(file));
//All read employees objects will be added to this list
List<Employee> employeeList = new ArrayList<>();
//Create Employee object. It will get all the data using setter methods.
//And at last, it will stored in above 'employeeList'
Employee employee = null;
// Checking the availability of the next tag
while (eventReader.hasNext())
{
XMLEvent xmlEvent = eventReader.nextEvent();
if (xmlEvent.isStartElement())
{
StartElement startElement = xmlEvent.asStartElement();
//As soo as employee tag is opened, create new Employee object
if("employee".equalsIgnoreCase(startElement.getName().getLocalPart())) {
employee = new Employee();
}
//Read all attributes when start tag is being read
@SuppressWarnings("unchecked")
Iterator<Attribute> iterator = startElement.getAttributes();
while (iterator.hasNext())
{
Attribute attribute = iterator.next();
QName name = attribute.getName();
if("id".equalsIgnoreCase(name.getLocalPart())) {
employee.setId(Integer.valueOf(attribute.getValue()));
}
}
//Now everytime content tags are found;
//Move the iterator and read data
switch (startElement.getName().getLocalPart())
{
case "name":
Characters nameDataEvent = (Characters) eventReader.nextEvent();
employee.setName(nameDataEvent.getData());
break;
case "title":
Characters titleDataEvent = (Characters) eventReader.nextEvent();
employee.setTitle(titleDataEvent.getData());
break;
}
}
if (xmlEvent.isEndElement())
{
EndElement endElement = xmlEvent.asEndElement();
//If employee tag is closed then add the employee object to list;
//and be ready to read next employee data
if("employee".equalsIgnoreCase(endElement.getName().getLocalPart())) {
employeeList.add(employee);
}
}
}
System.out.println(employeeList); //Verify read data
}
}
StAX (Streaming API for XML) 提供了两种解析 XML 的方式，例如：基于游标的 API 和基于迭代器的 API。
日期：2020-09-17 00:10:13 来源：oir作者：oir