黑马优化Servlet

问题：平常我们编写servlet的时候，经常会一个java文件写一个方法调用这样很麻烦，会写一堆的Servlet文件

解决方法：编写基本的baseservlet，之后其他的文件采用/Brand/*调用该方法，替换HttpServlet,根据请求的最后一段路径来进行方法分发

BaseServlet.java文件

package com.hailei.web.servlet;


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.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * 替换HttpServlet,根据请求的最后一段路径来进行方法分发
 */

public class BaseServlet extends HttpServlet {

    //根据请求的最后一段路径来进行方法分发
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1. 获取请求路径
        String uri = req.getRequestURI(); // /brand-case/brand/selectAll

        //2. 获取最后一段路径，方法名
        int index = uri.lastIndexOf('/');
        String methodName = uri.substring(index + 1); //  /selectAll? selectAll?

        //2. 执行方法
        //2.1 获取BrandServlet /UserServlet 字节码对象 Class

        Class<? extends BaseServlet> cls = this.getClass();
        //2.2 获取方法 Method对象
        try {
            Method method = cls.getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
            //2.3 执行方法
            method.invoke(this,req,resp);
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }


    }
}

之后，其他的就直接写后面就行

package com.hailei.web.servlet;


import com.alibaba.fastjson.JSON;
import com.hailei.pojo.Brand;
import com.hailei.pojo.PageBean;
import com.hailei.service.BrandService;
import com.hailei.service.impl.BrandServiceImpl;


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

@WebServlet("/brand/*")
public class BrandServlet extends BaseServlet{
    private BrandService brandService = new BrandServiceImpl();

    public void selectAll(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 调用service查询
        List<Brand> brands = brandService.selectAll();

        //2. 转为JSON
        String jsonString = JSON.toJSONString(brands);
        //3. 写数据
        response.setContentType("text/json;charset=utf-8");
        response.getWriter().write(jsonString);
    }
}

优势：只需要写一个Servlet就可以了，把方法往里面堆放就可以了