通过扩展 DefaultParser 来构建处理程序

package com.onitroad.xml.sax;
import java.util.ArrayList;
import java.util.Stack;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class UserParserHandler extends DefaultHandler
{
	//This is the list which shall be populated while parsing the XML.
    private ArrayList userList = new ArrayList();
    //As we read any XML element we will push that in this stack
    private Stack elementStack = new Stack();
    //As we complete one user block in XML, we will push the User instance in userList
    private Stack objectStack = new Stack();
    public void startDocument() throws SAXException
    {
        //System.out.println("start of the document   : ");
    }
    public void endDocument() throws SAXException
    {
        //System.out.println("end of the document document     : ");
    }
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException
    {
    	//Push it in element stack
        this.elementStack.push(qName);
        //If this is start of 'user' element then prepare a new User instance and push it in object stack
        if ("user".equals(qName))
        {
            //New User instance
        	User user = new User();
            //Set all required attributes in any XML element here itself
            if(attributes != null && attributes.getLength() == 1)
            {
            	user.setId(Integer.parseInt(attributes.getValue(0)));
            }
            this.objectStack.push(user);
        }
    }
    public void endElement(String uri, String localName, String qName) throws SAXException
    {
    	//Remove last added  element
        this.elementStack.pop();
        //User instance has been constructed so pop it from object stack and push in userList
        if ("user".equals(qName))
        {
            User object = this.objectStack.pop();
            this.userList.add(object);
        }
    }
    /**
     * This will be called everytime parser encounter a value node
     * */
    public void characters(char[] ch, int start, int length) throws SAXException
    {
        String value = new String(ch, start, length).trim();
        if (value.length() == 0)
        {
            return; // ignore white space
        }
        //handle the value based on to which element it belongs
        if ("firstName".equals(currentElement()))
        {
            User user = (User) this.objectStack.peek();
            user.setFirstName(value);
        }
        else if ("lastName".equals(currentElement()))
        {
            User user = (User) this.objectStack.peek();
            user.setLastName(value);
        }
    }
    /**
     * Utility method for getting the current element in processing
     * */
    private String currentElement()
    {
        return this.elementStack.peek();
    }
    //Accessor for userList object
    public ArrayList getUsers()
    {
    	return userList;
    }
}

SAX是一个XML流接口，这意味着使用SAX的应用程序可以接收有关正在处理的XML文档的事件通知—元素和属性，时间顺序从文档顶部开始，到根元素关闭为止。
这意味着它在线性时间内处理 XML 非常有效，而不会对系统内存提出太多要求。

SAX 解析器读取 XML 文件

package com.onitroad.xml.sax;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;
public class UsersXmlParser
{
	public ArrayList parseXml(InputStream in)
	{
		//Create a empty link of users initially
		ArrayList<user> users = new ArrayList</user><user>();
		try
		{
			//Create default handler instance
			UserParserHandler handler = new UserParserHandler();
			//Create parser from factory
			XMLReader parser = XMLReaderFactory.createXMLReader();
			//Register handler with parser
			parser.setContentHandler(handler);
			//Create an input source from the XML input stream
			InputSource source = new InputSource(in);
			//parse the document
			parser.parse(source);
			//populate the parsed users list in above created empty list; You can return from here also.
			users = handler.getUsers();
		} catch (SAXException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
		}
		return users;
	}
}

创建模型类

package com.onitroad.xml.sax;
/**
 * Model class. Its instances will be populated using SAX parser.
 * */
public class User
{
	//XML attribute id
	private int id;
	//XML element fisrtName
	private String firstName;
	//XML element lastName
	private String lastName;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getFirstName() {
		return firstName;
	}
	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}
	public String getLastName() {
		return lastName;
	}
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	@Override
	public String toString() {
		return this.id + ":" + this.firstName +  ":" +this.lastName ;
	}
}

测试 SAX 解析器

package com.onitroad.xml.sax;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.ArrayList;
public class TestSaxParser
{
	public static void main(String[] args) throws FileNotFoundException
	{
		//Locate the file
		File xmlFile = new File("D:/temp/sample.xml");
		//Create the parser instance
		UsersXmlParser parser = new UsersXmlParser();
		//Parse the file
		ArrayList users = parser.parseXml(new FileInputStream(xmlFile));
		//Verify the result
		System.out.println(users);
	}
}

要解析的xml测试文件

此 xml 文件还包含 xml 属性以及 xml 元素。

<users>
	<user id="100">
		<firstname>Tom</firstname>
		<lastname>Hanks</lastname>
	</user>
	<user id="101">
		<firstname>JackLi</firstname>
		<lastname>Gupta</lastname>
	</user>
	<user id="102">
		<firstname>HowToDo</firstname>
		<lastname>InJava</lastname>
	</user>
</users>