BaseServlet 继承 httpServlet

BaseServlet   核心

 package cn.core;

 import java.io.IOException;
 import java.lang.reflect.Method;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 /**
  * 1:继承HttpServlet让它成为Servlet<br>
  * 2:声明它的抽象的则是指这个类不能配置到web.xml中去<br>
  */
 public abstract class BaseServlet extends HttpServlet {
     /**
      * 3:直接重写service方法，以避免执行doGet/doPost分支
      */
     @Override
     public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         // 6:由于所有请求，都是先从这儿过去了，所以可以直接统一的设置请求编码和响应的类型
         req.setCharacterEncoding("UTF-8");
         resp.setContentType("text/html;charset=UTF-8");
         // 7:用户通过参数的形式通知调用哪一个方法?method=add调用add方法
         // 解析出这个参数
         String methodName = req.getParameter("method");
         if (methodName == null || methodName.trim().equals("")) {
             // 默认为exuecte
             methodName = "execute";
         }
         // 8:再通过反射调用子类方法,可以使用this反射出子类。
         // 反射出方法
         try {
             Method method = this.getClass().getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
             // 执行调用
             method.invoke(this, req,resp);
         } catch (Exception e) {
             throw new RuntimeException(e);
         }

     }

     /**
      * 4:开发一个默认的方法，如果用户没有指定执行哪一个方法，则默认就执行默认的这个方法
      * 5:将这个方法修改成抽象的，以避免继承BaseServlet的类忘记开发execute
      */
     public abstract void execute(HttpServletRequest req, HttpServletResponse resp) throws Exception;
 }

方法测试

 package cn.examples;

 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import cn.core.BaseServlet;

 public class PersonServlet extends BaseServlet {
     // http://localhost:9999/mvc/person
     @Override
     public void execute(HttpServletRequest req, HttpServletResponse resp) throws Exception {
         System.err.println("这是默认的execute...");
     }

     // http://localhost:9999/mvc/person?method=addPerson
     public void addPerson(HttpServletRequest req, HttpServletResponse resp) {
         System.err.println("this is add...");
     }

     // http://localhost:9999/mvc/person?method=upload
     public void upload(HttpServletRequest req, HttpServletResponse resp) {
         System.err.println("this is upload img...");
     }

     // http://localhost:9999/mvc/person?method=del
     public void del(HttpServletRequest rr, HttpServletResponse resp) {
         System.err.println("this is delete...");
     }
 }