用於讀取xml配置檔案的工具類XMLUtil：

XMLUtil.java:

import org.w3c.dom.*;
import javax.xml.parsers.*;
import org.xml.sax.SAXException;
import java.io.*;

    public class XMLUtils {
        public static Object getBean(){
            try {
                //建立文件物件
                DocumentBuilderFactory dFactory = DocumentBuilderFactory.newInstance();
                DocumentBuilder builder 
 
= dFactory.newDocumentBuilder();
                Document doc;
                doc = builder.parse(new File("src/BuilderPattern/utils/config.xml"));
                //獲取包含支付方式名稱的文字節點
                NodeList nl = doc.getElementsByTagName("className");
                Node classNode=nl.item(0).getFirstChild();
                String cName
 
=classNode.getNodeValue();
                //通過類名生成例項物件並將其返回
                Class c=Class.forName(cName);
                Object obj=c.newInstance();
                return obj;
            }catch (Exception e){
                e.printStackTrace();
                return null;
            }
        }
    }
 

config.xml:

<?xml version="1.0"?>
<config>
    <className>BuilderPattern.SubMealBuilder.SubMealBuilderA</className>
</config>