result

.gitignore

@@ -1,3 +1,4 @@
 .idea/*
 *.iml
 target/*
+*.log

log4j2.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="info">
+    <Appenders>
+        <Console name="Console" target="SYSTEM_OUT">
+            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
+        </Console>
+        <File name="File" fileName="logs/app.log">
+            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
+        </File>
+    </Appenders>
+    <Loggers>
+        <Root level="info">
+            <AppenderRef ref="Console"/>
+            <AppenderRef ref="File"/>
+        </Root>
+    </Loggers>
+</Configuration>

pom.xml

@@ -24,6 +24,11 @@
             <version>4.12</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-api</artifactId>
+            <version>2.23.1</version>
+        </dependency>
     </dependencies>
     <build>
         <plugins>

src/main/java/mate/academy/exception/AuthenticationException.java

@@ -1,8 +1,12 @@
 package mate.academy.exception;
 
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
 public class AuthenticationException extends Exception {
+    private static final Logger logger = LogManager.getLogger(AuthenticationException.class);
 
     public AuthenticationException(String message) {
-        super(message);
+        logger.error(message);
     }
 }

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

@@ -2,14 +2,17 @@
 
 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
         User user = findByLogin(login);
         if (!user.getPassword().equals(password)) {
-            throw new AuthenticationException("Username or password are incorrect");
+            logger.error("Login or password are incorrect. login={}", login);
         }
         return user;
     }

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

@@ -4,16 +4,21 @@
 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
         List<Product> products = getAllProductsFromShoppingCart(userId);
         Order order = new Order(products, userId);
         // NOTE: In production ready code this order identifier should be generated by DB
         // For test purpose we simplify this and return dummy data
         order.setOrderId(1L);
+        logger.info("Method login failed. Params: products={}, userId={}",
+                products, userId);
         return order;
     }
 
@@ -24,7 +29,7 @@ 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.info("Data from DB is fetched successful");
         return products;
     }
 }