旧式Servlet编程札记低质量

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# 旧Servlet + JSP用户管理项目

沐颜科技

在线用户剔除操作

WEB应用是一个多用户的使用环境，每一个用户都通过自己的session进行个人数据的记录，用户也可以手工进行注销操作，以实现session资源的释放，但是在一些系统中为了便于用户的管理，往往需要进行用户手工强制注销操作

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# 管理程序清单

No.	程序文件名称	类型	描述
1	/login.jsp	JSP	提供登录表单，以及错误显示
2	/pages/admin/online_user_list.jsp	JSP	管理员查看在线用户列表信息
3	/pages/front/welcome.jsp	JSP	用户登录成功后的欢迎页面
4	com.yootk.servlet.LoginServlet	Servlet	用户登录处理程序，密码为yootk表示登录成功
5	com.yootk.servlet.KickoutServlet	Servlet	在线用户剔除处理Servlet
6	com.yootk.listener.OnlineListener	Listener	监听器，在用户登录成功或注销后更新用户列表
7	com.yootk.filter.InvalidateFilter	Filter	登录失效检查，如果发现登录失效则跳转到登录页
8	com.yootk.filter.EncodingFilter	Filter	编码过滤器

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# 登录

@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String id = req.getParameter("userid"); // 接收请求参数
        String password = req.getParameter("password"); // 接收请求参数
        if (!"yootk".equals(password)) { // 密码输入错误
            req.setAttribute("error", "错误的用户名及密码！");
            req.getRequestDispatcher("/errors.jsp").forward(req, resp);
        }
        // WEB组件中提供有监听操作，而通过监听操作可以实现HttpSession属性的处理
        req.getSession().setAttribute("userid", id); // 设置Session属性内容
        resp.sendRedirect("/pages/front/welcome.jsp"); // 客户端跳转
    }
}

需要注意的是，此时并不是要完成一个简单的用户登录，而是需要对用户登录的状态进行
监听，因为最终要将登录的结果保
存在session属性之中，而session的内容又需要保存在application属性之中. .

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# 保存登录信息

@WebListener
public class OnlineListener implements ServletContextListener, HttpSessionListener, HttpSessionAttributeListener {
    private ServletContext servletContext; // 获取application实例
    @Override
    public void contextInitialized(ServletContextEvent sce) { // 进行初始化集合存储
        this.servletContext = sce.getServletContext(); // 存在有公共的application属性
        // Map集合之中的key表示用户名，而Value是保存当前的用户状态
        this.servletContext.setAttribute("online", new HashMap<String, Boolean>());
    }

    @Override
    public void attributeAdded(HttpSessionBindingEvent se) {
        // 用户登录成功会设置session的属性内容，这样就会触发本方法的执行
        if ("userid".equals(se.getName())) {    // 判断是否为指定的属性操作
            Map<String, Boolean> map = (Map<String, Boolean>) this.servletContext.getAttribute("online");
            map.put((String)se.getValue(), false); // 保存用户信息
            this.servletContext.setAttribute("online", map);
        }
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent se) { // 用户离开了
        Map<String, Boolean> map = (Map<String, Boolean>) this.servletContext.getAttribute("online");
        map.remove(se.getSession().getAttribute("userid")); // 删除数据
        this.servletContext.setAttribute("online", map);
    }
}

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# 在线用户列表

%@ page pageEncoding="UTF-8" import="java.util.*" %>
<%  // 通过request获取相关资源信息，拼凑成完整的访问路径
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" +
            request.getServerPort() + request.getContextPath() + "/" ;
%>
<html>
<head>
    <title>沐言科技：www.yootk.com</title>
    <base href="<%=basePath%>">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <script type="text/javascript" src="js/jquery.min.js"></script>
    <script type="text/javascript" src="bootstrap/js/bootstrap.min.js"></script>
    <link rel="stylesheet" type="text/css" href="bootstrap/css/bootstrap.min.css" />
</head>
<%!
    public static final String KICKOUT_URL = "/pages/admin/KickoutServlet";
%>
<body class="container">
<div class="row">
    <div class="panel panel-success">
        <div class="panel-heading">
            <strong><i class="fa fa-archive"></i>&nbsp;在线用户列表</strong>
        </div>
        <div class="panel-body">
            <%  // 获取当前全部的用户信息
                Map<String, Boolean> onlineMap = (Map<String, Boolean>) application.getAttribute("online"); // 获取Map集合
            %>
            <table class="table table-hover">
                <tr>
                    <th width="40%" class="text-center">用户名</th>
                    <th width="20%" class="text-center">状态</th>
                    <th width="10%" class="text-center">操作</th>
                </tr>
                <%
                    for (Map.Entry<String, Boolean> entry : onlineMap.entrySet()) {
                %>
                <tr>
                    <td class="text-center"><%=entry.getKey()%></td>
                    <td class="text-center">
                    <%
                        if (entry.getValue()) {
                    %>
                        <span class="label label-default">剔除</span>
                    <%
                        } else {
                    %>
                        <span class="label label-success">在线</span>
                    <%
                        }
                    %>
                    </td>
                    <td class="text-center">
                        <a class="btn btn-xs btn-danger" href="<%=KICKOUT_URL%>?userid=<%=entry.getKey()%>">
                            <span class="glyphicon glyphicon-remove"></span>&nbsp;强制下线</a></td>
                </tr>
                <%
                    }
                %>
            </table>
        </div>
        <div class="panel-footer">
            <div style="text-align:right;">
                <img src="images/logo.png" style="height: 30px;">
                <strong>沐言科技（www.yootk.com） —— 新时代软件教育领导品牌</strong>
            </div>
        </div>
    </div>
</div>
</body>
</html>

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# 注销

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@WebServlet("/pages/admin/KickoutServlet")
public class KickoutServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String userid = req.getParameter("userid");
        Map<String, Boolean> onlineMap = (Map<String, Boolean>) req.getServletContext().getAttribute("online"); // Map集合
        if (onlineMap.containsKey(userid)) {    // 用户还没走呢
            onlineMap.put(userid, true); // 设置为True就表示要剔除了
        }
        req.getServletContext().setAttribute("online", onlineMap);
        resp.sendRedirect("/pages/admin/online_user_list.jsp");
    }
}

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能够让用户注销的操作只能够是用户本身完成的事情，所以可以考虑做一个过滤器，过滤
器在用户每次访问的时候都判断一
下用户的状态，如果发现用户已经被删除了，则强制性的注销.

@WebFilter("/pages/front/*")
public class InvalidateFilter extends HttpFilter {
    @Override
    protected void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException {
        String userid = (String) request.getSession().getAttribute("userid");
        if (userid != null) {   // 用户登录过
            Map<String, Boolean> onlineMap = (Map<String, Boolean>) request.getServletContext().getAttribute("online"); // Map集合
            if (onlineMap.containsKey(userid)) {    // 用户还存在
                if (onlineMap.get(userid) == true) {    // 本身保存的就是布尔类型
                    request.getSession().invalidate(); // 强制注销
                    request.setAttribute("error", "您的账户已被系统强制下线，为了您的安全，请重新登录！");
                    request.getRequestDispatcher("/login.jsp").forward(request, response);
                } else {    // 正常的状态
                    chain.doFilter(request, response);
                }
            }
        } else {
            request.setAttribute("error", "您还未登录，请先登录！");
            request.getRequestDispatcher("/login.jsp").forward(request, response);
        }
    }
}

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# 旧Servlet SSM项目

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# 用户登录和注销接口开发

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//controller层代码
public void login(HttpServletRequest request,HttpServletResponse response){

        String phone = request.getParameter("phone");
        String pwd = request.getParameter("pwd");

        User user = userService.login(phone,pwd);

        if(user != null){

            request.getSession().setAttribute("loginUser",user);
            //跳转页面

        }else {

            request.setAttribute("msg","用户名或者密码不正确");

        }

}

//service层代码
@Override
public User login(String phone, String pwd) {

        String md5pwd = CommonUtil.MD5(pwd);

        User user = userDao.findByPhoneAndPwd(phone,md5pwd);

        return user;
}
  
  
//dao层代码
public User findByPhoneAndPwd(String phone, String md5pwd) {

        String sql = "select * from user where phone=? and pwd=?";

        User user = null;

        try{

            user = queryRunner.query(sql,new BeanHandler<>(User.class,processor),phone,md5pwd);

        }catch (Exception e){
            e.printStackTrace();
        }

        return user;
    }

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# 发布主题接口

   //controller层代码
    /**
     * http://localhost:8080/topic?method=addTopic
     * 发布主题
     * @param request
     * @param response
     */
    public void addTopic(HttpServletRequest request,HttpServletResponse response){

        User loginUser = (User)request.getSession().getAttribute("loginUser");
        if(loginUser == null){
            request.setAttribute("msg","请登录");
            return;
            //页面跳转 TODO
        }

        String title = request.getParameter("title");
        String content = request.getParameter("content");
        int cId = Integer.parseInt(request.getParameter("c_id"));

        int rows =  topicService.addTopic(loginUser,title,content,cId);

        if(rows ==1){

            //发布主题成功

        }else {

            //发布主题失败

        }

}



//service层代码
@Override
public int addTopic(User loginUser, String title, String content, int cId) {

        Category category = categoryDao.findById(cId);
        if(category == null){ return 0;}

        Topic topic = new Topic();
        topic.setTitle(title);
        topic.setContent(content);
        topic.setCreateTime(new Date());
        topic.setUpdateTime(new Date());
        topic.setPv(1);
        topic.setDelete(0);
        topic.setUserId(loginUser.getId());
        topic.setUsername(loginUser.getUsername());
        topic.setUserImg(loginUser.getImg());
        topic.setcId(cId);
        topic.setHot(0);

        int rows = 0;
        try {
            rows = topicDao.save(topic);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return rows;
}

//dao层代码
public int save(Topic topic) throws Exception {

String sql = "insert into topic(c_id,title,content,pv,user_id,username,user_img,create_time,update_time,hot,`delete`) " +"values(?,?,?,?,?,?,?,?,?,?,?)";

        Object [] params = {
                topic.getcId(),
                topic.getTitle(),
                topic.getContent(),
                topic.getPv(),
                topic.getUserId(),
                topic.getUsername(),
                topic.getUserImg(),
                topic.getCreateTime(),
                topic.getUpdateTime(),
                topic.getHot(),
                topic.getDelete()
        };
        int i =0;
        try{
            i= queryRunner.update(sql,params);

        }catch (Exception e){
            e.printStackTrace();
            throw new Exception();
        }
        return i;
    }

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# 回复盖楼功能开发

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Servlet-Service-Dao层开发

    //controller层代码
    /**
     * http://localhost:8080/topic?method=replyByTopicId&topic_id=9
     * 盖楼回复
     * @param request
     * @param response
     */
    public void replyByTopicId(HttpServletRequest request,HttpServletResponse response){

        User loginUser = (User)request.getSession().getAttribute("loginUser");
        if(loginUser == null){
            request.setAttribute("msg","请登录");
            return;
            //页面跳转 TODO
        }

        int topicId = Integer.parseInt(request.getParameter("topic_id"));

        String content = request.getParameter("content");


        int rows = topicService.replyByTopicId(loginUser,topicId,content);

        if(rows ==1){

            //回复成功

        }else {

            //回复失败

        }

    }

    //service层代码
    @Override
    public int replyByTopicId(User loginUser, int topicId, String content) {

        int floor = topicDao.findLatestFloorByTopicId(topicId);

        Reply reply = new Reply();
        reply.setContent(content);
        reply.setCreateTime(new Date());
        reply.setUpdateTime(new Date());
        reply.setFloor(floor+1);
        reply.setTopicId(topicId);
        reply.setUserId(loginUser.getId());
        reply.setUsername(loginUser.getUsername());
        reply.setUserImg(loginUser.getImg());
        reply.setDelete(0);

        int rows = replyDao.save(reply);

        return rows;
    }

//dao层代码
public int save(Reply reply) {

String sql = "insert into reply (topic_id,floor,content,user_id,username,user_img,create_time,update_time,`delete`)" +
"values (?,?,?,?,?,?,?,?,?)";

        Object [] params = {
                reply.getTopicId(),
                reply.getFloor(),
                reply.getContent(),
                reply.getUserId(),
                reply.getUsername(),
                reply.getUserImg(),
                reply.getCreateTime(),
                reply.getUpdateTime(),
                reply.getDelete()
        };

        int rows = 0;
        try{
            rows = queryRunner.update(sql,params);
        }catch (Exception e){
            e.printStackTrace();
        }

        return rows;
    }

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# topic阅读量递增

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通过session和topic进行绑定，一个session访问同个topic只算一次阅读

//controller层代码
//处理浏览量，如果同个session内只算一次
String sessionReadKey = "is_read_"+topicId;
Boolean isRead = (Boolean) request.getSession().getAttribute(sessionReadKey);

if(isRead == null){
      request.getSession().setAttribute(sessionReadKey,true);
      //新增一个pv
      topicService.addOnePV(topicId);

}

//service层代码
@Override
public void addOnePV(int topicId) {

        Topic topic = topicDao.findById(topicId);

        int newPV = topic.getPv()+1;

        topicDao.updatePV(topicId,newPV,topic.getPv());

}

//dao层代码
/**
* 更新浏览量
*/
public int updatePV(int topicId, int newPV, int oldPV) {
        String sql = "update topic set pv=? where pv=? and id=?";
        int rows = 0;
        try {
            rows =  queryRunner.update(sql,newPV,oldPV,topicId);
        }catch (Exception e){
            e.printStackTrace();
        }
        return rows;
}

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# 页自动跳转

简介：小滴课堂首页自动跳转配置

home.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>小滴课堂开发者论坛</title>
</head>
<body>


<jsp:forward page="/topic?method=list&c_id=1"></jsp:forward>

</body>
</html>

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web.xml

<welcome-file-list>
    <welcome-file>home.jsp</welcome-file>
  </welcome-file-list>

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# 用户登录校验拦截器开发

开发对应的登录拦截器

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开发loginInterceptor

登录校验成功放行

  /**
     * 进入到controller之前的方法
     * @param request
     * @param response
     * @param handler
     * @return
     * @throws Exception
     */
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        try {

            String accesToken = request.getHeader("token");
            if (accesToken == null) {
                accesToken = request.getParameter("token");
            }

            if (StringUtils.isNotBlank(accesToken)) {
                Claims claims = JWTUtils.checkJWT(accesToken);
                if (claims == null) {
                    //告诉登录过期，重新登录
                    sendJsonMessage(response, JsonData.buildError("登录过期，重新登录"));
                    return false;
                }

                Integer id = (Integer) claims.get("id");
                String name = (String) claims.get("name");

                request.setAttribute("user_id", id);
                request.setAttribute("name", name);

                return true;

            }

        }catch (Exception e){}

        sendJsonMessage(response, JsonData.buildError("登录过期，重新登录"));

        return false;
    }

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登录不成功返回json数据

 /**
     * 响应json数据给前端
     * @param response
     * @param obj
     */
public static void sendJsonMessage(HttpServletResponse response, Object obj){

        try{
            ObjectMapper objectMapper = new ObjectMapper();
            response.setContentType("application/json; charset=utf-8");
            PrintWriter writer = response.getWriter();
            writer.print(objectMapper.writeValueAsString(obj));
            writer.close();
            response.flushBuffer();
        }catch (Exception e){
            e.printStackTrace();
        }


    }

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# loginInterceptor注册和放行路径

loginInterceptor 拦截器注册和路径校验配置

继承 WebMvcConfigurer
配置拦截路径和放行路径

/**
 * 拦截器配置
 *
 * 不用权限可以访问url    /api/v1/pub/
 * 要登录可以访问url    /api/v1/pri/
 */

@Configuration
public class InterceptorConfig implements WebMvcConfigurer {


    @Bean
    LoginInterceptor loginInterceptor(){
        return new LoginInterceptor();
    }


    @Override
    public void addInterceptors(InterceptorRegistry registry) {

        //拦截全部
        registry.addInterceptor(loginInterceptor()).addPathPatterns("/api/v1/pri/*/*/**")
                //不拦截哪些路径   斜杠一定要加
                .excludePathPatterns("/api/v1/pri/user/login","/api/v1/pri/user/register");

        WebMvcConfigurer.super.addInterceptors(registry);

    }
}

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# Guava Cache缓存

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# 谷歌开源缓存框架Guava Cache讲解和封装缓存组件

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添加依赖

    <!--guava依赖包-->
    <dependency>
      <groupId>com.google.guava</groupId>
      <artifactId>guava</artifactId>
      <version>19.0</version>
    </dependency>

封装api

 private Cache<String,Object> tenMinuteCache = CacheBuilder.newBuilder()

            //设置缓存初始大小，应该合理设置，后续会扩容
            .initialCapacity(10)
            //最大值
            .maximumSize(100)
            //并发数设置
            .concurrencyLevel(5)

            //缓存过期时间，写入后10分钟过期
            .expireAfterWrite(600,TimeUnit.SECONDS)

            //统计缓存命中率
            .recordStats()

            .build();


    public Cache<String, Object> getTenMinuteCache() {
        return tenMinuteCache;
    }

    public void setTenMinuteCache(Cache<String, Object> tenMinuteCache) {
        this.tenMinuteCache = tenMinuteCache;
    }

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# 轮播图接口引入本地缓存

轮播图接口加入缓存

         try{

            Object cacheObj =  baseCache.getTenMinuteCache().get(CacheKeyManager.INDEX_BANNER_KEY, ()->{

                List<VideoBanner> bannerList =  videoMapper.listVideoBanner();

                System.out.println("从数据库里面找轮播图列表");

                return bannerList;

            });

            if(cacheObj instanceof List){
                List<VideoBanner> bannerList = (List<VideoBanner>)cacheObj;
                return bannerList;
            }

        }catch (Exception e){
            e.printStackTrace();
        }
        return null;

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# 视频列表引入本地缓存

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播放列表加入本地缓存

@Override
    public List<Video> listVideo() {


        try{

          Object cacheObj =  baseCache.getTenMinuteCache().get(CacheKeyManager.INDEX_VIDEL_LIST,()->{

                List<Video> videoList = videoMapper.listVideo();

                return videoList;

            });

          if(cacheObj instanceof List){
              List<Video> videoList = (List<Video>)cacheObj;
              return videoList;
          }

        }catch (Exception e){
            e.printStackTrace();
        }

        //可以返回兜底数据，业务系统降级-》SpringCloud专题课程
        return null;
    }

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# 视频详情引入本地缓存

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视频详情加入本地缓存

    @Override
    public Video findDetailById(int videoId) {

        String videoCacheKey = String.format(CacheKeyManager.VIDEO_DETAIL,videoId);

        try{

         Object cacheObject = baseCache.getOneHourCache().get( videoCacheKey, ()->{

                // 需要使用mybaits关联复杂查询
                Video video = videoMapper.findDetailById(videoId);

                return video;

            });

         if(cacheObject instanceof Video){

             Video video = (Video)cacheObject;
             return video;
         }

        }catch (Exception e){
            e.printStackTrace();
        }

        return null;
    }

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# 实战接口压力测试, 明白优化前后的QPS并发差距和跨域配置

# 开启Guava缓存压测热点数据接口

简介: 启用缓存压测热点数据接接口

视频轮播图接口 Throughput: 14000
注意：接口的性能影响因素很多：机器的配置如CPU、内存、当前负载情况等，还有网络带宽因素影响，只能尽量减少影响因素

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单线程访问结果

{"code":0,"data":null,"msg":null}

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# 取消Guava缓存压测热点数据接口和前后对比

简介: 不启用缓存压测热点数据接口

视频轮播图接口 Throughput : 2700

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