项目实战：设置静态资源放行

 1、DispatcherServlet

package com.csdn.mymvc.core;
import jakarta.servlet.RequestDispatcher;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Arrays;
@WebServlet("/*")
public class DispatcherServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String[] staticResourceSuffixes = {".html", ".jsp", ".jpg", ".png", ".gif", ".css", ".js", ".ico"};
        String uri = req.getRequestURI();
        if (Arrays.stream(staticResourceSuffixes).anyMatch(uri::endsWith)) {
            RequestDispatcher defaultDispatcher = req.getServletContext().getNamedDispatcher("default");
            defaultDispatcher.forward(req,resp);
        }
    }
}

 2、web.xml

The default servlet for all web applications, that serves static  
resources.  It processes all requests that are not mapped to other
servlets with servlet mappings (defined either here or in your own
web.xml file).
默认servlet是所有Web应用程序的默认servlet，用于提供静态资源。
它处理所有未映射到其他servlet的请求，
这些servlet映射（在此处或您自己的web.xml文件中定义）。

    <servlet>
        <servlet-name>defaultservlet-name>
        <servlet-class>org.apache.catalina.servlets.DefaultServletservlet-class>
        <init-param>
            <param-name>debugparam-name>
            <param-value>0param-value>
        init-param>
        <init-param>
            <param-name>listingsparam-name>
            <param-value>falseparam-value>
        init-param>
        <load-on-startup>1load-on-startup>
    servlet>

2、FruitServlet 

package com.csdn.fruit.servlet;
import com.csdn.fruit.dto.PageInfo;
import com.csdn.fruit.dto.PageQueryParam;
import com.csdn.fruit.dto.Result;
import com.csdn.fruit.pojo.Fruit;
import com.csdn.fruit.service.FruitService;
import com.csdn.fruit.service.impl.FruitServiceImpl;
import com.csdn.fruit.util.RequestUtil;
import com.csdn.fruit.util.ResponseUtil;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/fruit/*")
public class FruitServlet extends HttpServlet {
    private FruitService fruitService = new FruitServiceImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //     /fruit/index
        String uri = req.getRequestURI();
        uri = uri.substring(1);
        String[] split = uri.split("/");
        String methodName = split[1];
        switch (methodName) {
            case "index" ->index(req,resp);
            case "add"-> add(req, resp);
            case "del"->del(req,resp);
            case "edit"->edit(req,resp);
            case "getFname"-> getFname(req, resp);
            case "update"  -> update(req, resp);
        }
    }
 
    protected void index(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Integer pageNo = 1;
        String pageNoStr = req.getParameter("pageNo");
        if (pageNoStr != null && !"".equals(pageNoStr)) {
            pageNo = Integer.parseInt(pageNoStr);
        }
 
        String keyword = "";
        String keywordStr = req.getParameter("keyword");
        if (keywordStr != null) {
            keyword = keywordStr;
        }
        PageQueryParam pageQueryParam = new PageQueryParam(pageNo, 5, keyword);
        PageInfo pageInfo = fruitService.getFruitPageInfo(pageQueryParam);
 
        Result result = Result.OK(pageInfo);
 
        ResponseUtil.print(resp, result);
    }
 
    protected void add(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Fruit fruit = (Fruit) RequestUtil.readObject(req, Fruit.class);
        fruitService.addFruit(fruit);
        ResponseUtil.print(resp, Result.OK());
    }
 
    protected void del(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Integer fid = Integer.parseInt(req.getParameter("fid"));
        fruitService.delFruit(fid);
        ResponseUtil.print(resp, Result.OK());
    }
 
    protected void edit(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Integer fid = Integer.parseInt(req.getParameter("fid"));
        Fruit fruit = fruitService.getFruitById(fid);
        ResponseUtil.print(resp, Result.OK(fruit));
    }
 
    public void getFname(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String fname = req.getParameter("fname");
        Fruit fruit = fruitService.getFruitByFname(fname);
        ResponseUtil.print(resp, fruit == null ? Result.OK() : Result.Fail());
    }
 
    protected void update(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Fruit fruit = (Fruit) RequestUtil.readObject(req, Fruit.class);
        fruitService.updateFruit(fruit);
        ResponseUtil.print(resp, Result.OK());
    }
}