BAEL-1567 (#3824)

* BAEL-1412 add java 8 spring data features

* BAEL-21 new HTTP API overview

* BAEL-21 fix executor

* BAEL-1432 add custom gradle task

* BAEL-1567 add samples of cookie and session in serlvet

* BAEL-1567 use stream api

javax-servlets/src/main/java/com/baeldung/servlets/CookieReader.java

@@ -0,0 +1,39 @@
+package com.baeldung.servlets;
+
+import javax.servlet.http.Cookie;
+import javax.servlet.http.HttpServletRequest;
+import java.util.Arrays;
+
+/**
+ * Created by adam.
+ *
+ * Class which simplifies reading cookies from request.
+ */
+public class CookieReader {
+
+    private HttpServletRequest request;
+
+    /**
+     * The constructor.
+     *
+     * @param request request from which cookies will be read
+     */
+    public CookieReader(HttpServletRequest request) {
+        this.request = request;
+    }
+
+    /**
+     * Reads cookie by key from request.
+     *
+     * @param key the key of a cookie
+     * @return returns cookie value (or null if cookie with given key does not exist)
+     */
+    public String readCookie(String key) {
+        return Arrays.stream(request.getCookies())
+                 .filter(c -> key.equals(c.getName()))
+                 .map(Cookie::getValue)
+                 .findFirst()
+                 .orElse(null);
+    }
+
+}

javax-servlets/src/main/java/com/baeldung/servlets/LoginServlet.java

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+package com.baeldung.servlets;
+
+import javax.servlet.RequestDispatcher;
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.*;
+import java.io.IOException;
+
+/**
+ * Created by adam.
+ */
+@WebServlet(name = "LoginServlet", urlPatterns = "/login")
+public class LoginServlet extends HttpServlet {
+
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        CookieReader cookieReader = new CookieReader(request);
+        String uiColor = cookieReader.readCookie("uiColor");
+        String userName = cookieReader.readCookie("userName");
+
+        request.setAttribute("uiColor", uiColor != null ? uiColor : "blue");
+
+        if (userName == null || userName.isEmpty()) {
+            RequestDispatcher dispatcher = request.getRequestDispatcher("/WEB-INF/jsp/login.jsp");
+            dispatcher.forward(request, response);
+        } else {
+            response.sendRedirect("/welcome");
+        }
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
+        HttpSession session = request.getSession();
+        session.setAttribute("sampleKey", "Sample Value");
+
+        String uiColor = request.getParameter("color");
+        String userName = request.getParameter("name");
+
+        Cookie uiColorCookie = new Cookie("uiColor", uiColor);
+        response.addCookie(uiColorCookie);
+
+        Cookie userNameCookie = new Cookie("userName", userName);
+        response.addCookie(userNameCookie);
+
+        response.sendRedirect("/welcome");
+    }
+
+}

javax-servlets/src/main/java/com/baeldung/servlets/WelcomeServlet.java

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+package com.baeldung.servlets;
+
+import javax.servlet.RequestDispatcher;
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.Cookie;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+/**
+ * Created by adam.
+ */
+@WebServlet(name = "WelcomeServlet", urlPatterns = "/welcome")
+public class WelcomeServlet extends HttpServlet {
+
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        CookieReader cookieReader = new CookieReader(request);
+        String uiColor = cookieReader.readCookie("uiColor");
+        String userName = cookieReader.readCookie("userName");
+
+        if (userName == null || userName.isEmpty()) {
+            response.sendRedirect("/login");
+        } else {
+            request.setAttribute("uiColor", uiColor != null ? uiColor : "blue");
+            request.setAttribute("userName", userName);
+            request.setAttribute("sessionAttribute", request.getSession().getAttribute("sampleKey"));
+
+            RequestDispatcher dispatcher = request.getRequestDispatcher("/WEB-INF/jsp/welcome.jsp");
+            dispatcher.forward(request, response);
+        }
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
+        Cookie userNameCookieRemove = new Cookie("userName", "");
+        userNameCookieRemove.setMaxAge(0);
+        response.addCookie(userNameCookieRemove);
+
+        response.sendRedirect("/login");
+    }
+
+}

javax-servlets/src/main/webapp/WEB-INF/jsp/login.jsp

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+<%@ page contentType="text/html;charset=UTF-8"%>
+<html>
+<head>
+    <title>Hello New User:</title>
+</head>
+<body style="background: ${uiColor}">
+    <form name="userForm" action="login" method="POST">
+        <label>Your Name:</label>
+        <input type="text" name="name"/>
+
+        <label>UI Color:</label>
+        <input type="text" name="color"/>
+
+        <button type="submit">Confirm</button>
+    </form>
+</body>
+</html>

javax-servlets/src/main/webapp/WEB-INF/jsp/welcome.jsp

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+<%@ page contentType="text/html;charset=UTF-8"%>
+<html>
+<head>
+    <title>Hello Known User:</title>
+</head>
+<body style="background: ${uiColor}">
+    <form action="welcome" method="POST">
+        <label>Your name: ${userName}</label>
+        <label>Session param: ${sessionAttribute}</label>
+        <button type="submit">Logout</button>
+    </form>
+</body>
+</html>