根据xml配置使用反射动态生成对象

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://www.example.org/web-app_2_5"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.example.org/web-app_2_5 web-app_2_5.xsd"
    version="2.5">

    <servlet>
        <servlet-name>helloServlet</servlet-name>
        <servlet-class>cn.sasa.web01.servlet.Hello</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>helloServlet</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>hiServlet</servlet-name>
        <servlet-class>cn.sasa.web01.servlet.Hi</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>hiServlet</servlet-name>
        <url-pattern>/hi</url-pattern>
    </servlet-mapping>
</web-app>

创建一个接口，其实现类实现接口的方法

package cn.sasa.web01.servlet;

public interface IMyServlet {
    public void init();
    public void service();
    public void destory();
}

创建两个实现类Hello、Hi实现IMyServlet接口

package cn.sasa.web01.servlet;

public class Hello implements IMyServlet {

    @Override
    public void init() {
        System.out.println("hello----init");
    }

    @Override
    public void service() {
        System.out.println("hello----service");
    }

    @Override
    public void destory() {
        System.out.println("hello----destory");
    }

}

package cn.sasa.web01.servlet;

public class Hi implements IMyServlet {

    @Override
    public void init() {
        System.out.println("hi----init");
    }

    @Override
    public void service() {
        System.out.println("hi----service");
    }

    @Override
    public void destory() {
        System.out.println("hi----destory");
    }

}

测试：

package cn.sasa.web01.servlet;

import java.lang.reflect.Method;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class Test {
    public static void main(String[] args) {
        SAXReader reader = new SAXReader();
//        try {
//            Document doc = reader.read("src/cn/sasa/web01/servlet/web.xml");
//            Element root = doc.getRootElement();
//            Element servElement = root.element("servlet");
//            String className = servElement.element("servlet-class").getText();
//            //System.out.println(str);
//            Class c1 = Class.forName(className);
//            hello obj = (hello)c1.newInstance();
//            obj.init();
//            obj.service();
//            obj.destory();
//        } catch (Exception e) {
//            // TODO Auto-generated catch block
//            e.printStackTrace();
//        }

        try {
            //获取xml文档对象
            Document doc = reader.read("src/cn/sasa/web01/servlet/web.xml");
            //获取根节点
            Element root = doc.getRootElement();
            List<Element> chilNodes = root.elements();
            for(Element e : chilNodes) {
                if("servlet".equals(e.getName())) {
                    //获取类全名
                    String className = e.element("servlet-class").getText();
                    //反射获取字节文件对象
                    Class c = Class.forName(className);
                    //生成对象
                    Object obj = c.newInstance();
                    //获取方法
                    Method init = c.getMethod("init", null);
                    //运行
                    init.invoke(obj, null);

                    Method service = c.getMethod("service", null);
                    service.invoke(obj, null);

                    Method destory = c.getMethod("destory", null);
                    destory.invoke(obj, null);
                }
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}