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...");
    }
}