Add servlets and UI for a Tic-Tac-Toe game

src/main/java/com/tictactoe/InitServlet.java

@@ -0,0 +1,29 @@
+package com.tictactoe;
+
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpSession;
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+
+@WebServlet(name = "InitServlet", value = "/start")
+public class InitServlet extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        HttpSession currentSession = req.getSession(true);
+
+        Field field = new Field();
+        Map<Integer, Sign> fieldData = field.getField();
+
+        List<Sign> data = field.getFieldData();
+
+        currentSession.setAttribute("field", field);
+        currentSession.setAttribute("data", data);
+
+        getServletContext().getRequestDispatcher("/index.jsp").forward(req, resp);
+    }
+}

src/main/java/com/tictactoe/LogicServlet.java

@@ -0,0 +1,90 @@
+package com.tictactoe;
+
+import javax.servlet.RequestDispatcher;
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpSession;
+import java.io.IOException;
+import java.util.List;
+
+@WebServlet(name = "LogicServlet", value = "/logic")
+public class LogicServlet extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
+        HttpSession currentSession = req.getSession();
+
+        Field field = extractField(currentSession);
+
+        int index = getSelectedIndex(req);
+        Sign currentSign = field.getField().get(index);
+
+        if (Sign.EMPTY != currentSign) {
+            RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/index.jsp");
+            dispatcher.forward(req, resp);
+            return;
+        }
+
+        field.getField().put(index, Sign.CROSS);
+        if (checkWin(resp, currentSession, field)) {
+            return;
+        }
+
+        int emptyFieldIndex = field.getEmptyFieldIndex();
+
+        if (emptyFieldIndex >= 0) {
+            field.getField().put(emptyFieldIndex, Sign.NOUGHT);
+            if (checkWin(resp, currentSession, field)) {
+                return;
+            }
+        } else {
+            currentSession.setAttribute("draw", true);
+
+            List<Sign> data = field.getFieldData();
+
+            currentSession.setAttribute("data", data);
+
+            resp.sendRedirect("/index.jsp");
+            return;
+        }
+
+
+        List<Sign> data = field.getFieldData();
+
+        currentSession.setAttribute("data", data);
+        currentSession.setAttribute("field", field);
+
+        resp.sendRedirect("/index.jsp");
+    }
+
+    private Field extractField(HttpSession currentSession) {
+        Object fieldAttribute = currentSession.getAttribute("field");
+        if (Field.class != fieldAttribute.getClass()) {
+            currentSession.invalidate();
+            throw new RuntimeException("Session is broken, try one more time");
+        }
+        return (Field) fieldAttribute;
+    }
+
+    private int getSelectedIndex(HttpServletRequest req) {
+        String click = req.getParameter("click");
+        boolean isNumeric = click.chars().allMatch(Character::isDigit);
+        return isNumeric ? Integer.parseInt(click) : 0;
+    }
+
+    private boolean checkWin(HttpServletResponse response, HttpSession currentSession, Field field) throws IOException {
+        Sign winner = field.checkWin();
+        if (Sign.CROSS == winner || Sign.NOUGHT == winner) {
+            currentSession.setAttribute("winner", winner);
+            List<Sign> data = field.getFieldData();
+
+            currentSession.setAttribute("data", data);
+            response.sendRedirect("/index.jsp");
+
+            return true;
+        }
+        return false;
+    }
+}

src/main/java/com/tictactoe/RestartServlet.java

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+package com.tictactoe;
+
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+@WebServlet(name = "RestartServlet", value = "/restart")
+public class RestartServlet extends HttpServlet {
+    @Override
+    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+        req.getSession().invalidate();
+        resp.sendRedirect("/start");
+    }
+}

src/main/webapp/index.jsp

@@ -1,16 +1,65 @@
+<%@ page import="com.tictactoe.Sign" %>
 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 
 <!DOCTYPE html>
 <html>
 <head>
     <title>Tic-Tac-Toe</title>
+    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
+    <link href="static/main.css" rel="stylesheet">
+    <script src="<c:url value="/static/jquery-3.6.0.min.js"/>"></script>
+
 </head>
 <body>
 <h1>Tic-Tac-Toe</h1>
+<table>
+    <tr>
+        <td onclick="window.location='/logic?click=0'">${data.get(0).getSign()}</td>
+        <td onclick="window.location='/logic?click=1'">${data.get(1).getSign()}</td>
+        <td onclick="window.location='/logic?click=2'">${data.get(2).getSign()}</td>
+    </tr>
+    <tr>
+        <td onclick="window.location='/logic?click=3'">${data.get(3).getSign()}</td>
+        <td onclick="window.location='/logic?click=4'">${data.get(4).getSign()}</td>
+        <td onclick="window.location='/logic?click=5'">${data.get(5).getSign()}</td>
+    </tr>
+    <tr>
+        <td onclick="window.location='/logic?click=6'">${data.get(6).getSign()}</td>
+        <td onclick="window.location='/logic?click=7'">${data.get(7).getSign()}</td>
+        <td onclick="window.location='/logic?click=8'">${data.get(8).getSign()}</td>
+    </tr>
+</table>
 
+<hr>
+<c:set var="CROSSES" value="<%=Sign.CROSS%>"/>
+<c:set var="NOUGHTS" value="<%=Sign.NOUGHT%>"/>
 
-<script>
+<c:if test="${winner == CROSSES}">
+    <h1>CROSSES WIN!</h1>
+    <button onclick="restart()">Start again</button>
+</c:if>
+<c:if test="${winner == NOUGHTS}">
+    <h1>NOUGHTS WIN!</h1>
+    <button onclick="restart()">Start again</button>
+</c:if>
+<c:if test="${draw}">
+    <h1>IT'S A DRAW</h1>
+    <br>
+    <button onclick="restart()">Start again</button>
+</c:if>
 
+<script>
+    function restart() {
+        $.ajax({
+            url: '/restart',
+            type: 'POST',
+            contentType: 'application/json;charset=UTF-8',
+            async: false,
+            success: function () {
+                location.reload();
+            }
+        });
+    }
 </script>
 
 </body>

src/main/webapp/static/main.css

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+td {
+    border: 3px solid black;
+    padding: 10px;
+    border-collapse: separate;
+    margin: 10px;
+    width: 100px;
+    height: 100px;
+    font-size: 50px;
+    text-align: center;
+    empty-cells: show;
+}