java后端-强哥带你写旅游网-05BaseServlet的增加

建立BaseServlet

当前项目的是一个功能就会对应到一个Servelt，若继续这样做，随着功能的增多，就会产生很多的Servlet，让无疑就会产生很多的重复代码，作为软件开发人员，我不应该让项目里有太多重复性的东西，因此决定抽出来一个基类，来减少Sevlet的创建。

具体如何做呢？请看如下BaseServlet的代码

public class BaseServlet extends HttpServlet {


    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //System.out.println("baseServlet的service方法被执行了...");

        //完成方法分发
        //1.获取请求路径
        String uri = req.getRequestURI(); //   /travel/user/add
        //System.out.println("请求uri:"+uri);//  /travel/user/add
        //2.获取方法名称
        String methodName = uri.substring(uri.lastIndexOf('/') + 1);
        //System.out.println("方法名称："+methodName);
        //3.获取方法对象Method
        //谁调用我？我代表谁
       // System.out.println(this);//UserServlet的对象cn.itcast.travel.web.servlet.UserServlet@4903d97e
        try {
            //获取方法
            Method method = this.getClass().getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
            //4.执行方法
            //暴力反射
            //method.setAccessible(true);
            method.invoke(this,req,resp);
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }


    }

    /**
     * 直接将传入的对象序列化为json，并且写回客户端
     * @param obj
     */
    public void writeValue(Object obj,HttpServletResponse response) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        response.setContentType("application/json;charset=utf-8");
        mapper.writeValue(response.getOutputStream(),obj);
    }

    /**
     * 将传入的对象序列化为json，返回
     * @param obj
     * @return
     */
    public String writeValueAsString(Object obj) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        return mapper.writeValueAsString(obj);
    }

}

紧接着创建UserServlet,具体代码如下

@WebServlet("/user/*") // /user/add /user/find
public class UserServlet extends BaseServlet {

    //声明UserService业务对象
    private UserService service = new UserServiceImpl();

    /**
     * 注册功能
     * @param request
     * @param response
     * @throws ServletException
     * @throws IOException
     */
    public void regist(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //验证校验
        String check = request.getParameter("check");
        //从sesion中获取验证码
        HttpSession session = request.getSession();
        String checkcode_server = (String) session.getAttribute("CHECKCODE_SERVER");
        session.removeAttribute("CHECKCODE_SERVER");//为了保证验证码只能使用一次
        //比较
        if(checkcode_server == null || !checkcode_server.equalsIgnoreCase(check)){
            //验证码错误
            ResultInfo info = new ResultInfo();
            //注册失败
            info.setFlag(false);
            info.setErrorMsg("验证码错误");
            //将info对象序列化为json
            ObjectMapper mapper = new ObjectMapper();
            String json = mapper.writeValueAsString(info);
            response.setContentType("application/json;charset=utf-8");
            response.getWriter().write(json);
            return;
        }

        //1.获取数据
        Map map = request.getParameterMap();

        //2.封装对象
        User user = new User();
        try {
            BeanUtils.populate(user,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        //3.调用service完成注册
        //UserService service = new UserServiceImpl();
        boolean flag = service.regist(user);
        ResultInfo info = new ResultInfo();
        //4.响应结果
        if(flag){
            //注册成功
            info.setFlag(true);
        }else{
            //注册失败
            info.setFlag(false);
            info.setErrorMsg("注册失败!");
        }

        //将info对象序列化为json
        ObjectMapper mapper = new ObjectMapper();
        String json = mapper.writeValueAsString(info);

        //将json数据写回客户端
        //设置content-type
        response.setContentType("application/json;charset=utf-8");
        response.getWriter().write(json);

    }

    /**
     * 登录功能
     * @param request
     * @param response
     * @throws ServletException
     * @throws IOException
     */
    public void login(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.获取用户名和密码数据
        Map map = request.getParameterMap();
        //2.封装User对象
        User user = new User();
        try {
            BeanUtils.populate(user,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        //3.调用Service查询
       // UserService service = new UserServiceImpl();
        User u  = service.login(user);

        ResultInfo info = new ResultInfo();

        //4.判断用户对象是否为null
        if(u == null){
            //用户名密码或错误
            info.setFlag(false);
            info.setErrorMsg("用户名密码或错误");
        }
        //5.判断用户是否激活
        if(u != null && !"Y".equals(u.getStatus())){
            //用户尚未激活
            info.setFlag(false);
            info.setErrorMsg("您尚未激活，请激活");
        }
        //6.判断登录成功
        if(u != null && "Y".equals(u.getStatus())){
            request.getSession().setAttribute("user",u);//登录成功标记

            //登录成功
            info.setFlag(true);
        }

        //响应数据
        ObjectMapper mapper = new ObjectMapper();

        response.setContentType("application/json;charset=utf-8");
        mapper.writeValue(response.getOutputStream(),info);
    }

    /**
     * 查询单个对象
     * @param request
     * @param response
     * @throws ServletException
     * @throws IOException
     */
    public void findOne(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //从session中获取登录用户
        Object user = request.getSession().getAttribute("user");
        //将user写回客户端

       /* ObjectMapper mapper = new ObjectMapper();
        response.setContentType("application/json;charset=utf-8");
        mapper.writeValue(response.getOutputStream(),user);*/
       writeValue(user,response);
    }

    /**
     * 退出功能
     * @param request
     * @param response
     * @throws ServletException
     * @throws IOException
     */
    public void exit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.销毁session
        request.getSession().invalidate();

        //2.跳转登录页面
        response.sendRedirect(request.getContextPath()+"/login.html");
    }

    /**
     * 激活功能
     * @param request
     * @param response
     * @throws ServletException
     * @throws IOException
     */
    public void active(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.获取激活码
        String code = request.getParameter("code");
        if(code != null){
            //2.调用service完成激活
            //UserService service = new UserServiceImpl();
            boolean flag = service.active(code);

            //3.判断标记
            String msg = null;
            if(flag){
                //激活成功
                msg = "激活成功，请登录";
            }else{
                //激活失败
                msg = "激活失败，请联系管理员!";
            }
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write(msg);
        }
    }
}

此时，你发现UserServlet是继承于BaseServlet，然后将之前其他Servlet中的功能作为方法移植到UserServlet对应的方法中了。

同时UserServlet的路径，也不再是写死的，而是一个灵活可变的/user/*，当你在浏览器中输入/user/regist，就会调用到UserServlet对应的regist方法，在浏览器中输入/user/exit,就会调用到UserServlet对应的exit方法。之前一个Servlet只对应一个功能，而现在一个Servlet可以对应多个功能。

删除之前的Servlet，删除之后，只剩下，如下

此时，重新运行项目，你会发现登陆功能不能用了，这是因为，我已经改变了Servlet的路径，所以你肯定访问不了，所以，你应该重新指定登陆的路径，登陆指定如下

注册重新指定路径

header中，用户名的获取，重新指定路径

header中，退出登录，路径重新指定

邮件激活路径更改

项目地址https://gitee.com/cxyhq2020/Mytravel.git