java summarizes the parsing of XML files the addition and deletion of nodes

1. java code:
dom is mainly used for operation

 
package test; 
import java.io.IOException; 
import javax.xml.parsers.DocumentBuilder; 
import javax.xml.parsers.DocumentBuilderFactory; 
import javax.xml.parsers.ParserConfigurationException; 
import javax.xml.transform.Transformer; 
import javax.xml.transform.TransformerConfigurationException; 
import javax.xml.transform.TransformerException; 
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.NodeList; 
import org.w3c.dom.Text; 
import org.xml.sax.SAXException; 
public class XmlOprate { 
Document doc; 
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); 
DocumentBuilder builder; 
NodeList imags; 
String path; 
public NodeList getImags() { 
return imags; 
} 
public void setImags(NodeList imags) { 
this.imags = imags; 
} 
/** 
*  A constructor  
* @param path:xml Path to file  
* @param nodes : to be analyzed xml The name of the node  
*/ 
public XmlOprate(String path) { 
super(); 
this.path = path; 
System.out.println(System.getProperty("user.dir")); 
} 
/** 
*  parsing XML 
* @param path 
*/ 
public void readXml(){ 
try { 
builder = factory.newDocumentBuilder(); 
Document doc=builder.parse(path); 
doc.normalize(); 
NodeList imags =doc.getElementsByTagName("imags"); 
this.setImags(imags); 
for (int i=0;i<imags.getLength();i++){ 
Element link=(Element) imags.item(i); 
System.out.print("title: "); 
System.out.println(link.getElementsByTagName("title").item(0).getFirstChild().getNodeValue()); 
System.out.print("URL: "); 
System.out.println(link.getElementsByTagName("url").item(0).getFirstChild().getNodeValue()); 
System.out.print("imgsrc: "); 
System.out.println(link.getElementsByTagName("imgsrc").item(0).getFirstChild().getNodeValue()); 
System.out.println(); 
} 
}catch (ParserConfigurationException e) { 
e.printStackTrace(); 
} catch (SAXException e) { 
e.printStackTrace(); 
} catch (IOException e) { 
e.printStackTrace(); 
} 
} 
/** 
* addCode 
* @param path 
*/ 
public void addXmlCode(String imgsrc,String title,String url){ 
try { 
builder = factory.newDocumentBuilder(); 
Document doc=builder.parse(path); 
doc.normalize(); 
Text textseg; 
Element imag=doc.createElement("imags"); 
Element linkimgsrc=doc.createElement("imgsrc"); 
textseg=doc.createTextNode(imgsrc); 
linkimgsrc.appendChild(textseg); 
imag.appendChild(linkimgsrc); 
Element linktitle=doc.createElement("title"); 
textseg=doc.createTextNode(title); 
linktitle.appendChild(textseg); 
imag.appendChild(linktitle); 
Element linkurl=doc.createElement("url"); 
textseg=doc.createTextNode(url); 
linkurl.appendChild(textseg); 
imag.appendChild(linkurl); 
doc.getDocumentElement().appendChild(imag); 
TransformerFactory tFactory =TransformerFactory.newInstance(); 
Transformer transformer; 
transformer = tFactory.newTransformer(); 
DOMSource source = new DOMSource(doc); 
StreamResult result = new StreamResult(new java.io.File(path)); 
transformer.transform(source, result); 
}catch(Exception e){ 
} 
} 
/** 
* delete xml code 
* @param path 
*/ 
public void delXmlCode(){ 
try { 
builder = factory.newDocumentBuilder(); 
doc=builder.parse(path); 
doc.normalize(); 
NodeList imags =doc.getElementsByTagName("imags"); 
Element elink=(Element) imags.item(0); 
elink.removeChild(elink.getElementsByTagName("imgsrc").item(0)); 
elink.removeChild(elink.getElementsByTagName("title").item(0)); 
elink.removeChild(elink.getElementsByTagName("url").item(0)); 
doc.getFirstChild().removeChild(elink); 
TransformerFactory tFactory =TransformerFactory.newInstance(); 
Transformer transformer = tFactory.newTransformer(); 
DOMSource source = new DOMSource(doc); 
StreamResult result = new StreamResult(new java.io.File(path)); 
transformer.transform(source, result); 
} catch (ParserConfigurationException e) { 
e.printStackTrace(); 
} catch (SAXException e) { 
e.printStackTrace(); 
} catch (IOException e) { 
e.printStackTrace(); 
} catch (TransformerConfigurationException e) { 
e.printStackTrace(); 
} catch (TransformerException e) { 
e.printStackTrace(); 
} 
} 
} 

2. xml part

 
<?xml version="1.0" encoding="UTF-8" ?> 
<root> 
<imags> 
<imgsrc>images/ad-01.jpg</imgsrc> 
<title> Ho chi minh city </title> 
<url>http://torchrelay.beijing2008.cn/cn/journey/hochiminhcity/</url> 
</imags> 
<imags> 
<imgsrc>images/ad-02.jpg</imgsrc> 
<title> Hong Kong 2</title> 
<url>http://torchrelay.beijing2008.cn/cn/journey/hongkong/</url> 
</imags> 
</root> 

3. Conclusion:
Look at the three methods for xml operations (read, write, delete), and they all have the same initialization statement:

 
builder = factory.newDocumentBuilder(); 
Document doc=builder.parse(path); 
doc.normalize(); 

At first I tried to take the same part out and write it in the constructor, but in my tests, I found that this always reported a null pointer error.
I just put the
builder = factory.newDocumentBuilder();
When placed in an builder initialization statement, it reads fine, but it also reports errors when written or deleted.
So I'm going to write it like this, and it feels a little bit messy, but I didn't think of any good way to do it, so I'm going to stick it here, and it might be useful, right