Счётчик нажатий

Для этого можем реализовать определенную логику в сервлете, который отвечает за необходимую страницу.

Класс PageVisitsCounterDemo.java

package net.proselyte.servletstutorial;

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.io.PrintWriter;

/**
 * Simple servlet that counts page visits.
 *
 * @author Eugene Suleimanov
 */

public class PageVisitsCounterDemo extends HttpServlet {
    private volatile int visitsCounter;

    public void init() {
        visitsCounter = 0;
    }

    synchronized void increaseAmountOfVisits() {
        visitsCounter++;
    }

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

        increaseAmountOfVisits();

        response.setContentType("text/html");

        String docType = "
<
!DOCTYPE html
>
";
        String title = "Visits Counter Demo";
        PrintWriter writer = response.getWriter();

        writer.println(docType + "
<
html
>
" +
                "
<
head
>
" +
                "
<
title
>
" + title +
                "
<
/title
>
" +
                "
<
/head
>
" +
                "
<
body
>
" +
                "
<
h1
>
Visits amount: 
<
/h1
>
" +
                visitsCounter +
                "
<
/body
>
" +
                "
<
/html
>
");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

Файл web.xml

<
!DOCTYPE web-app PUBLIC
        "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
        "http://java.sun.com/dtd/web-app_2_3.dtd" 
>
<
web-app
>
<
display-name
>
Servlets Tutorial
<
/display-name
>
<
servlet
>
<
servlet-name
>
SimpleServlet
<
/servlet-name
>
<
servlet-class
>
net.proselyte.servletstutorial.SimpleServlet
<
/servlet-class
>
<
/servlet
>
<
servlet
>
<
servlet-name
>
PageVisitsCounterDemo
<
/servlet-name
>
<
servlet-class
>
net.proselyte.servletstutorial.PageVisitsCounterDemo
<
/servlet-class
>
<
/servlet
>
<
servlet-mapping
>
<
servlet-name
>
SimpleServlet
<
/servlet-name
>
<
url-pattern
>
/SimpleServlet
<
/url-pattern
>
<
/servlet-mapping
>
<
servlet-mapping
>
<
servlet-name
>
PageVisitsCounterDemo
<
/servlet-name
>
<
url-pattern
>
/PageVisitsCounterDemo
<
/url-pattern
>
<
/servlet-mapping
>
<
/web-app
>

Выполним в консоли команду:

mvn tomcat7:run

Откроем браузер и перейдем по ссылке:

http://localhost:8088/PageVisitsCounterDemo

В результате получим следующую страницу: