solution

.gitignore

@@ -1,3 +1,5 @@
 .idea/*
 *.iml
 target/*
+logs/app.log
+

pom.xml

@@ -3,11 +3,9 @@
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
-
     <groupId>mate-academy</groupId>
     <artifactId>jv-logger</artifactId>
     <version>1.0-SNAPSHOT</version>
-
     <properties>
         <jdk.version>17</jdk.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
@@ -16,14 +14,18 @@
             https://raw.githubusercontent.com/mate-academy/style-guides/master/java/checkstyle.xml
         </maven.checkstyle.plugin.configLocation>
     </properties>
-
     <dependencies>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <version>4.12</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-core</artifactId>
+            <version>2.14.1</version>
+        </dependency>
     </dependencies>
     <build>
         <plugins>
@@ -62,5 +64,4 @@
             </plugins>
         </pluginManagement>
     </build>
-</project>
-
+</project>

src/main/java/mate/academy/Main.java

@@ -6,15 +6,18 @@
 import mate.academy.service.AuthenticationServiceImpl;
 import mate.academy.service.OrderService;
 import mate.academy.service.OrderServiceImpl;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 
 public class Main {
     public static void main(String[] args) {
+        final Logger logger = LogManager.getLogger(Main.class);
         AuthenticationService authenticationService = new AuthenticationServiceImpl();
         User user;
         try {
             user = authenticationService.login("bob", "1234");
         } catch (AuthenticationException e) {
-            e.printStackTrace();
+            logger.error("Authentication failed for user. Reason: {}", e.getMessage());
             return;
         }
         OrderService orderService = new OrderServiceImpl();

src/main/java/mate/academy/resources/log4j2.xml

@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="info">
+    <Appenders>
+        <!-- Console Appender -->
+        <Console name="LogToConsole" target="SYSTEM_OUT">
+            <PatternLayout>
+                <Pattern>%d{HH:mm:ss.SS} %-5level %logger{36} - %msg%n</Pattern>
+            </PatternLayout>
+        </Console>
+        <!-- File Appender: Automatically creates the 'logs' directory and 'app.log' file -->
+        <File name="LogToFile" fileName="logs/app.log">
+            <PatternLayout>
+                <Pattern>%d %p %c:%L %m%n</Pattern>
+            </PatternLayout>
+        </File>
+    </Appenders>
+
+    <Loggers>
+        <!-- Define logger for specific package -->
+        <Logger name="mate.academy" level="info" additivity="false">
+            <AppenderRef ref="LogToFile"/>
+            <AppenderRef ref="LogToConsole"/>
+        </Logger>
+
+        <!-- Root Logger -->
+        <Root level="error">
+            <AppenderRef ref="LogToFile"/>
+            <AppenderRef ref="LogToConsole"/>
+        </Root>
+    </Loggers>
+</Configuration>

src/main/java/mate/academy/service/AuthenticationServiceImpl.java

@@ -2,11 +2,15 @@
 
 import mate.academy.exception.AuthenticationException;
 import mate.academy.model.User;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 
 public class AuthenticationServiceImpl implements AuthenticationService {
+    private static final Logger logger = LogManager.getLogger(AuthenticationServiceImpl.class);
+
     @Override
     public User login(String login, String password) throws AuthenticationException {
-        //TODO: add corresponding log message about method login was called
+        logger.debug("Login method was called. Params: login ={}", login);
         User user = findByLogin(login);
         if (!user.getPassword().equals(password)) {
             throw new AuthenticationException("Username or password are incorrect");

src/main/java/mate/academy/service/OrderServiceImpl.java

@@ -4,11 +4,15 @@
 import java.util.List;
 import mate.academy.model.Order;
 import mate.academy.model.Product;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 
 public class OrderServiceImpl implements OrderService {
+    private static final Logger logger = LogManager.getLogger(OrderServiceImpl.class);
+
     @Override
     public Order completeOrder(Long userId) {
-        // TODO: add log message about method completeOrder was called
+        logger.debug("completeOrder method was called. UserID = {}", userId);
         List<Product> products = getAllProductsFromShoppingCart(userId);
         Order order = new Order(products, userId);
         // NOTE: In production ready code this order identifier should be generated by DB
@@ -24,7 +28,7 @@ private List<Product> getAllProductsFromShoppingCart(Long userId) {
         Product macBook = new Product("MacBook Air 2020", BigDecimal.valueOf(1399));
         Product xiaomi = new Product("Xiaomi 12", BigDecimal.valueOf(499));
         List<Product> products = List.of(iphone, macBook, xiaomi);
-        // TODO: add log message about successful fetched data from DB
+        logger.debug("Method getAllProductsFromShoppingCart was called. UserID = {}",userId);
         return products;
     }
 }