利用JDK_API发现错误原因

package cn.itcast.jaxp;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

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

import cn.itcast.utils.JaxpDomUtil;

/**
 * JAXP的DOM解析XML
 * @author Administrator
 *
 */
public class JaxpDomTest {
	
	public static void main(String[] args) {
		try {
			run2();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	public static void run2() throws Exception{
		// 获取工厂类
		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
		// 获取解析器
		DocumentBuilder builder = factory.newDocumentBuilder();
		// 解析xml，返回document对象
		Document document = builder.parse("src/book2.xml");
		// 获取第二本书
		Node book2 = document.getElementsByTagName("书").item(1);
		// 创建元素对象
		Element chubanshe = document.createElement("出版社");
		// 设置文本内容
		chubanshe.setTextContent("人民出版社");
		//在book2中添加出版社标签
		book2.appendChild(chubanshe);
		
        //使用insertbefore方法想把出版社标签插入到售价标签前面时报错
		Node shoujia = book2.getChildNodes().item(2);
		document.insertBefore(chubanshe, shoujia);
		
		// 回写
		// 创建回写类的工厂
		TransformerFactory transformerFactory =  TransformerFactory.newInstance();
		// 获取回写类
		Transformer transformer = transformerFactory.newTransformer();
		// 调用回写的方法
		transformer.transform(new DOMSource(document), new StreamResult("src/book2.xml"));
	}
}