java之DocumentBuilderFactory解析xml

1、About documentBuilderFactory API description

1）、 javax.xml.parsers 包DocumentBuilderFactory创建DOM模式的解析器对象, DocumentBuilderFactory是抽象工厂类，不能直接实例化，但是有newInstance方法


2）、DocumentBuilderFactory.newInstance() 得到创建 DOM 解析器的工厂

DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance()

3）、newDocumentBuilder方法得到 DOM 解析器对象

DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();

4)、DOM解析器解析输入流，这里可以是XML，文档转化为输入流，或者字符串转为ByteArrayInputStream,DOM 解析器对象的 parse() 方法解析 XML 文档，得到代表整个文档的 Document 对象

InputStream is = new FileInputStream("xxx.xml");
documentBuilder.parse(is);
documentBuilder.parse(new ByteArrayInputStream(str.getBytes())); 

 
5)、得到 XML 文档的根节点

Element rootElement = document.getDocumentElement();

6)、得到节点的子节点

NodeList studentInfo = appElement.getChildNodes();

2、Test Demo

Student.java文件

package com.parse.doc;

public class Student {
	
	public String name;
	public String age;
	public String sex;
	public Student() {}
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	@Override
	public String toString() {
		return "name=" + name + ", age=" + age + ", sex=" + sex;
	}
}

ParseXml.java文件

package com.parse.doc;

import java.io.ByteArrayInputStream;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;


public class ParseXml {
	
	public static String xml = "";
	public static final String STUDENT = "student";
	public static final String NAME = "name";
	public static final String AGE = "age";
	public static final String SEX = "sex";
	
	public static void main(String args[]) {
		List students = parseXmlByDoc(xml);
		if (students != null && students.size() > 0) {
			for (Student student : students) {
				System.out.println(student);
			}
		} else {
			System.out.println("students size is 0");
		}
		
	}
	
	public static List parseXmlByDoc(String str) {
		if (str == null || "".equals(str)) {
			System.out.println("str is null or ''");
			return null;
		}
		DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
		List students = new ArrayList();
		DocumentBuilder documentBuilder;
		try {
			documentBuilder = documentBuilderFactory.newDocumentBuilder();
			Document document = documentBuilder.parse(new ByteArrayInputStream(str.getBytes()));
			Element rootElement = document.getDocumentElement();
			NodeList studentNodeList = rootElement.getElementsByTagName(STUDENT);
			for (int i = 0; i < studentNodeList.getLength(); i++) {
				Element appElement = (Element) studentNodeList.item(i);
				NodeList studentInfo = appElement.getChildNodes();
				Student student = new Student();
				for(int j = 0; j < studentInfo.getLength(); j++) { 
					Element element = (Element) studentInfo.item(j);
					String appAttr = element.getTagName();
					switch (appAttr) {
						case NAME:
							student.setName(element.getTextContent());
							break;
						case AGE:
							student.setAge(element.getTextContent());
							break;
						case SEX:
							student.setSex(element.getTextContent());
							break;
						default:
							break;
					} 
				}
				students.add(student);
			}
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
		return students;
	}
}

3、Running results

name=陈喻, age=26, sex=男
name=陈彩凤, age=25, sex=女
name=陈紫宣, age=2, sex=女
name=陈紫曦, age=7个月, sex=女