15. Servlet入门 - 统计网站被访问的总次数

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发布于 2022-01-14 17:46:08

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发布于 2022-01-14 17:46:08

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15. Servlet入门 - 统计网站被访问的总次数

需求

在页面中显示您是第x位访问的用户.

思路分析

image-20191208160926430

代码实现

1.CountServlet 实现 count 总次数在 ServletContext 的计数

image-20201228005843990

@WebServlet(name = "CountServlet", value = "/count")
public class CountServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 读取Servlet中的count参数
        ServletContext servletContext = getServletContext();
        Object count = servletContext.getAttribute("count");

        //2. 判断count参数是否存在，如果不存在，则初始化，设置为0；反之，加 1
        if (count == null) {
            count = 0;
            servletContext.setAttribute("count", count);
        }

        int number = (int) count + 1;
        System.out.println("number: " + number);
        servletContext.setAttribute("count", number);

        //3.返回浏览器 Welcome
        response.getWriter().write("Welcome...." + number);
    }
}

启动 tomcat 服务，访问测试如下：

http://localhost:8080/demo01/count

image-20201228005910378

2.ShowServlet 实现读取 ServletContext 的 count 总计数

image-20201228010038457

@WebServlet(name = "ShowServlet", value = "/show")
public class ShowServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 1. 读取ServletContext中的count总次数
        ServletContext servletContext = getServletContext();
        int count = (int)servletContext.getAttribute("count");

        // 2. 返回浏览器访问的总次数
        response.setContentType("text/html; charset=UTF-8"); // 设置浏览器以utf8编码格式，不然中文显示为乱码
        response.getWriter().print("您是第 " + count + "  位访问的用户");
    }
}

访问 http://localhost:8080/demo01/show 测试如下：