RDBMS 数据库读取数据写进xml

import java.io.File;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
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.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;


public class Append {
public static void main(String[] args) throws Exception {
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document doc=builder.parse("MyXml.xml");
doc.normalize();
Element root=doc.getDocumentElement();
acessDB(doc,root);
if(doc!=null)
printNode(root);
TransformerFactory tf=TransformerFactory.newInstance();
Transformer transformer=tf.newTransformer();
DOMSource source=new DOMSource(doc);
        StreamResult result=new StreamResult(new File("MyXml.xml"));
        transformer.transform(source, result);



}

public static void acessDB(Document doc,Element root) throws Exception{
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://127.0.0.1/xml?useUnicode=true&characterEncoding=utf-8";
Connection conn=DriverManager.getConnection(url, "", "");
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery("select * from users");
createXML(doc,root,rs);
}

public static void createXML(Document doc,Element root,ResultSet rs) throws Exception{
boolean flag=rs.next();
while(flag){
Element Users=doc.createElement("Users");
Element userid=doc.createElement("userid");
Text userid_text=doc.createTextNode(""+rs.getInt("userid"));
userid.appendChild(userid_text);
Element username=doc.createElement("usrrname");

Text username_text=doc.createTextNode(rs.getString("username"));
username.appendChild(userid_text);
Element password=doc.createElement("password");
Text password_text=doc.createTextNode(rs.getString("password"));
password.appendChild(password_text);

Users.appendChild(userid);
Users.appendChild(username);
Users.appendChild(password);
root.appendChild(Users);
flag=rs.next();



}

}

public static void printNode(Element element){
NodeList children=element.getChildNodes();
NamedNodeMap attr=element.getAttributes();
int r=children.getLength();
if(attr!=null){
System.out.print("<"+element.getNodeName());
for(int j=0;j<attr.getLength();j++){
System.out.print(" "+attr.item(j).getNodeName()+"="+attr.item(j).getNodeName()+" ");

}
System.out.println(">");

}else if(attr==null){
System.out.println("<"+element.getNodeName()+">");

}
if(element.hasChildNodes()){
for(int k=0;k<r;k++){
if(children.item(k).getNodeType()==Node.ELEMENT_NODE)
printNode((Element)children.item(k));
else if(children.item(k).getNodeType()==Node.TEXT_NODE){
System.out.println(children.item(k).getNodeValue());

}

}
System.out.println("</"+element.getNodeName()+">");

}
}

}需要注意的是:导入mysql-connect-java.jar包，
             新建的 xml文件在项目的根目录下，
             需要包含一个标签和头文件
             如：<?xml version="1.0" encoding="UTF-8" standalone="no"? ><b></b> 否则会有如下异常：[Fatal Error] *.xml:1:1: Premature end of file.