类似sax解析,但
sax解析一旦开始解析就是从头读到尾 ,不解析完整个文档不会停
pull解析较为灵活 是以时间为单位 手动向下继续 如果获得我们要找的结果 可以停止解析
基于事件驱动，

基本套路：
通过工厂实例 获取解析器 
解析器可以判断头尾标签 可以判断标签名 可以获取属性或者内容

------------------
xml文件:
<students>
	<student id="111">
	    <name>zhangsan</name>
	    <age>13</age>
	</student>
	<student id="222">
	    <name>lisi</name>
	    <age>14</age>
	</student>
</students>

java类:
import java.io.FileInputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserFactory;

public class PullTools {
	public static List<Student> PullTool(InputStream is) throws Exception {
		List<Student> list = new ArrayList<>();
		Student stu = null;
		XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
		XmlPullParser parser = factory.newPullParser();
		parser.setInput(is, "utf-8");
		for (int type = parser.getEventType(); type != XmlPullParser.END_DOCUMENT; type = parser.next()) {
			switch (type) {
			case XmlPullParser.START_TAG:
				switch (parser.getName()) {
				case "student":
					stu = new Student();
					int id = Integer.parseInt(parser.getAttributeValue(0));
					stu.setId(id);
					break;
				case "name":
					String name = parser.nextText();
					stu.setName(name);
					break;
				case "age":
					int age = Integer.parseInt(parser.nextText());
					stu.setAge(age);
					break;
				}
				break;
			case XmlPullParser.END_TAG:
				if ("student".equals(parser.getName())) {
					list.add(stu);
				}
				break;
			}
		}
		return list;
	}

	public static void main(String[] args) throws Exception {
		InputStream is = new FileInputStream("stu.xml");
		List<Student> list = PullTools.PullTool(is);
		is.close();
		System.out.println(list);
	}
}
	
public class Student {
	private int id;
	private String name;
	private int age;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
	}

}