Fix server session

double-buffer/src/main/java/com/iluwatar/doublebuffer/Pixel.java

@@ -30,5 +30,5 @@
 public enum Pixel {
 
   WHITE,
-  BLACK;
+  BLACK
 }

pom.xml

@@ -219,6 +219,7 @@
     <module>dynamic-proxy</module>
     <module>gateway</module>
     <module>slob</module>
+    <module>server-session</module>
   </modules>
   <repositories>
     <repository>

server-session/README.md

@@ -3,9 +3,9 @@ title: Server Session
 category: Behavioral
 language: en
 tag:
-    - Session Management 
-    - Session Tracking
     - Cookies
+    - Session management 
+    - State tracking
 ---
 
 ## Also known as
@@ -20,7 +20,7 @@ Within the context of a client-server relationship, the server is responsible fo
 
 Real-world example
 
-> Consider a gaming website which stores user profile data such as username, password, highscore, hours played, etc. Since this website is accessed over the internet which uses the HTTP protocol, all requests sent to the server are stateless. In order for the page to display user relevent information without re-authenticating the user on every request a session must be created. Once the session is created the user can access the homescreen, statistics page, setting page, etc. and view profile specific data without needing to login in on every page request.
+> Consider a gaming website which stores user profile data such as username, password, high-score, hours played, etc. Since this website is accessed over the internet which uses the HTTP protocol, all requests sent to the server are stateless. In order for the page to display user relevant information without re-authenticating the user on every request a session must be created. Once the session is created the user can access the homescreen, statistics page, setting page, etc. and view profile specific data without needing to log in on every page request.
 
 In plain words
 
@@ -179,13 +179,13 @@ Sessions are often given a maximum time in which they will be maintained. The se
 
 ## Class diagram
 
-![alt text](./etc/adapter.urm.png "Adapter class diagram")
+![Server Session class diagram](./etc/server-session.urm.puml "Server Session class diagram")
 
 ## Applicability
 
 Use the Adapter pattern when
 
-* When a user logs into a website or web application and you want to keep track of their authentication status.
+* When a user logs into a website or web application, and you want to keep track of their authentication status.
 * In e-commerce websites when you want to maintain the contents of a user's shopping cart across different pages and visits.
 * When you want to store user preferences and settings, such as language preferences, theme choices, or any other customizable options. 
 * When you want to keep track of user activity and behavior on a website for the sake of analytics purposes.

server-session/etc/server-session.urm.puml

@@ -0,0 +1,27 @@
+@startuml
+package com.iluwatar.sessionserver {
+  class App {
+    - LOGGER : Logger {static}
+    - SESSION_EXPIRATION_TIME : long {static}
+    - sessionCreationTimes : Map<String, Instant> {static}
+    - sessions : Map<String, Integer> {static}
+    + App()
+    + main(args : String[]) {static}
+    - sessionExpirationTask() {static}
+  }
+  class LoginHandler {
+    - LOGGER : Logger {static}
+    - sessionCreationTimes : Map<String, Instant>
+    - sessions : Map<String, Integer>
+    + LoginHandler(sessions : Map<String, Integer>, sessionCreationTimes : Map<String, Instant>)
+    + handle(exchange : HttpExchange)
+  }
+  class LogoutHandler {
+    - LOGGER : Logger {static}
+    - sessionCreationTimes : Map<String, Instant>
+    - sessions : Map<String, Integer>
+    + LogoutHandler(sessions : Map<String, Integer>, sessionCreationTimes : Map<String, Instant>)
+    + handle(exchange : HttpExchange)
+  }
+}
+@enduml

server-session/pom.xml

@@ -9,19 +9,17 @@
         <artifactId>java-design-patterns</artifactId>
         <version>1.26.0-SNAPSHOT</version>
     </parent>
-    <artifactId>serversession</artifactId>
+    <artifactId>server-session</artifactId>
 
     <dependencies>
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>
-            <version>5.10.2</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>
-            <version>5.11.0</version>
             <scope>test</scope>
         </dependency>
     </dependencies>

server-session/src/main/java/com/iluwatar/sessionserver/App.java

@@ -1,10 +1,12 @@
 package com.iluwatar.sessionserver;
 
+import com.sun.net.httpserver.HttpServer;
 import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.time.Instant;
-import java.util.*;
-import com.sun.net.httpserver.HttpServer;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
 import lombok.extern.slf4j.Slf4j;
 
 /**
@@ -32,48 +34,54 @@ public class App {
   private static Map<String, Instant> sessionCreationTimes = new HashMap<>();
   private static final long SESSION_EXPIRATION_TIME = 10000;
 
-    public static void main(String[] args) throws IOException {
-      // Create HTTP server listening on port 8000
-      HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
+  /**
+   * Main entry point.
+   * @param args arguments
+   * @throws IOException ex
+   */
+  public static void main(String[] args) throws IOException {
+    // Create HTTP server listening on port 8000
+    HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
 
-      // Set up session management endpoints
-      server.createContext("/login", new LoginHandler(sessions, sessionCreationTimes));
-      server.createContext("/logout", new LogoutHandler(sessions, sessionCreationTimes));
+    // Set up session management endpoints
+    server.createContext("/login", new LoginHandler(sessions, sessionCreationTimes));
+    server.createContext("/logout", new LogoutHandler(sessions, sessionCreationTimes));
 
-      // Start the server
-      server.start();
+    // Start the server
+    server.start();
 
-      // Start background task to check for expired sessions
-      sessionExpirationTask();
+    // Start background task to check for expired sessions
+    sessionExpirationTask();
 
-      LOGGER.info("Server started. Listening on port 8080...");
-    }
+    LOGGER.info("Server started. Listening on port 8080...");
+  }
 
-    private static void sessionExpirationTask() {
-        new Thread(() -> {
-            while (true) {
-                try {
-                    LOGGER.info("Session expiration checker started...");
-                    Thread.sleep(SESSION_EXPIRATION_TIME); // Sleep for expiration time
-                    Instant currentTime = Instant.now();
-                    synchronized (sessions) {
-                        synchronized (sessionCreationTimes) {
-                            Iterator<Map.Entry<String, Instant>> iterator = sessionCreationTimes.entrySet().iterator();
-                            while (iterator.hasNext()) {
-                                Map.Entry<String, Instant> entry = iterator.next();
-                                if (entry.getValue().plusMillis(SESSION_EXPIRATION_TIME).isBefore(currentTime)) {
-                                    sessions.remove(entry.getKey());
-                                    iterator.remove();
-                                }
-                            }
-                        }
-                    }
-                    LOGGER.info("Session expiration checker finished!");
-                } catch (InterruptedException e) {
-                    LOGGER.error("An error occurred: ", e);
-                    Thread.currentThread().interrupt();
+  private static void sessionExpirationTask() {
+    new Thread(() -> {
+      while (true) {
+        try {
+          LOGGER.info("Session expiration checker started...");
+          Thread.sleep(SESSION_EXPIRATION_TIME); // Sleep for expiration time
+          Instant currentTime = Instant.now();
+          synchronized (sessions) {
+            synchronized (sessionCreationTimes) {
+              Iterator<Map.Entry<String, Instant>> iterator =
+                  sessionCreationTimes.entrySet().iterator();
+              while (iterator.hasNext()) {
+                Map.Entry<String, Instant> entry = iterator.next();
+                if (entry.getValue().plusMillis(SESSION_EXPIRATION_TIME).isBefore(currentTime)) {
+                  sessions.remove(entry.getKey());
+                  iterator.remove();
                 }
+              }
             }
-        }).start();
-    }
+          }
+          LOGGER.info("Session expiration checker finished!");
+        } catch (InterruptedException e) {
+          LOGGER.error("An error occurred: ", e);
+          Thread.currentThread().interrupt();
+        }
+      }
+    }).start();
+  }
 }

server-session/src/main/java/com/iluwatar/sessionserver/LoginHandler.java

@@ -2,53 +2,52 @@
 
 import com.sun.net.httpserver.HttpExchange;
 import com.sun.net.httpserver.HttpHandler;
-import lombok.extern.slf4j.Slf4j;
-import org.slf4j.Logger;
-
 import java.io.IOException;
 import java.io.OutputStream;
 import java.time.Instant;
-import java.util.HashMap;
 import java.util.Map;
 import java.util.UUID;
+import lombok.extern.slf4j.Slf4j;
 
+/**
+ * LoginHandler.
+ */
 @Slf4j
 public class LoginHandler implements HttpHandler {
 
-    private Map<String, Integer> sessions;
-    private Map<String, Instant> sessionCreationTimes;
-
-    public LoginHandler(Map<String, Integer> sessions, Map<String, Instant> sessionCreationTimes) {
-        this.sessions = sessions;
-        this.sessionCreationTimes = sessionCreationTimes;
+  private Map<String, Integer> sessions;
+  private Map<String, Instant> sessionCreationTimes;
+
+  public LoginHandler(Map<String, Integer> sessions, Map<String, Instant> sessionCreationTimes) {
+    this.sessions = sessions;
+    this.sessionCreationTimes = sessionCreationTimes;
+  }
+
+  @Override
+  public void handle(HttpExchange exchange) {
+    // Generate session ID
+    String sessionId = UUID.randomUUID().toString();
+
+    // Store session data (simulated)
+    int newUser = sessions.size() + 1;
+    sessions.put(sessionId, newUser);
+    sessionCreationTimes.put(sessionId, Instant.now());
+    LOGGER.info("User " + newUser + " created at time " + sessionCreationTimes.get(sessionId));
+
+    // Set session ID as cookie
+    exchange.getResponseHeaders().add("Set-Cookie", "sessionID=" + sessionId);
+
+    // Send response
+    String response = "Login successful!\n" + "Session ID: " + sessionId;
+    try {
+      exchange.sendResponseHeaders(200, response.length());
+    } catch (IOException e) {
+      LOGGER.error("An error occurred: ", e);
     }
-
-    @Override
-    public void handle(HttpExchange exchange) {
-        // Generate session ID
-        String sessionID = UUID.randomUUID().toString();
-
-        // Store session data (simulated)
-        int newUser = sessions.size() + 1;
-        sessions.put(sessionID, newUser);
-        sessionCreationTimes.put(sessionID, Instant.now());
-        LOGGER.info("User " + newUser + " created at time " + sessionCreationTimes.get(sessionID));
-
-        // Set session ID as cookie
-        exchange.getResponseHeaders().add("Set-Cookie", "sessionID=" + sessionID);
-
-        // Send response
-        String response = "Login successful!\n" +
-                "Session ID: " + sessionID;
-        try {
-          exchange.sendResponseHeaders(200, response.length());
-        } catch (IOException e) {
-          LOGGER.error("An error occurred: ", e);
-        }
-        try(OutputStream os = exchange.getResponseBody()) {
-          os.write(response.getBytes());
-        } catch(IOException e) {
-          LOGGER.error("An error occurred: ", e);
-        }
+    try (OutputStream os = exchange.getResponseBody()) {
+      os.write(response.getBytes());
+    } catch (IOException e) {
+      LOGGER.error("An error occurred: ", e);
     }
+  }
 }