封装Servlet统一处理请求

1、编写baseController
2、子类继承baseController

前端需要每次传入action表示需要执行controller中的方法

baseController

package com.cn.fb.controller;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;


public class baseController extends HttpServlet {

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            // 设置请求响应的字符集编码格式
            request.setCharacterEncoding("utf-8");
            response.setCharacterEncoding("utf-8");
            // 前端传入需要执行的方法名参数
            String action = request.getParameter("action");
            // 获取类对象
            Class clazz = this.getClass();
            // 通过反射获取方法
            Method declaredMethod = clazz.getDeclaredMethod(action, HttpServletRequest.class, HttpServletResponse.class);
            // 执行方法并且获取返回值
            Object object = declaredMethod.invoke(this, request, response);
            // 判断返回值
            if (object != null && object instanceof String) {
                String url = (String) object;
                if (url.startsWith("f:")) {
                    // 请求转发
                    request.getRequestDispatcher(url.substring(2)).forward(request, response);
                } else if (url.startsWith("r:")) {
                    // 重定向
                    response.sendRedirect(url.substring(2));
                } else {
                    // 返回字符串或JSON到浏览器
                    PrintWriter writer = response.getWriter();
                    writer.print(url);
                    writer.flush();
                    writer.close();
                }
            }
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }
}

子类

package com.cn.fb.controller;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


@WebServlet(value = "/user")
public class UserController extends baseController {

    public String selectAll(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        return "f:list.jsp";
    }
}