feat: configure logging and replace println/stacktraces

.gitignore

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

pom.xml

@@ -24,7 +24,14 @@
             <version>4.12</version>
             <scope>test</scope>
         </dependency>
+        <!-- Logging -->
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>1.2.17</version>
+        </dependency>
     </dependencies>
+
     <build>
         <plugins>
             <plugin>
@@ -62,5 +69,4 @@
             </plugins>
         </pluginManagement>
     </build>
-</project>
-
+</project>

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

@@ -6,18 +6,22 @@
 import mate.academy.service.AuthenticationServiceImpl;
 import mate.academy.service.OrderService;
 import mate.academy.service.OrderServiceImpl;
+import org.apache.log4j.Logger;
 
 public class Main {
+    private static final Logger logger = Logger.getLogger(Main.class);
+
     public static void main(String[] args) {
         AuthenticationService authenticationService = new AuthenticationServiceImpl();
         User user;
         try {
             user = authenticationService.login("bob", "1234");
         } catch (AuthenticationException e) {
-            e.printStackTrace();
+            logger.error("Authentication failed for user 'bob'", e);
             return;
         }
         OrderService orderService = new OrderServiceImpl();
         orderService.completeOrder(user.getUserId());
+        logger.info("Order processing finished for userId=" + user.getUserId());
     }
 }

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

@@ -2,22 +2,26 @@
 
 import mate.academy.exception.AuthenticationException;
 import mate.academy.model.User;
+import org.apache.log4j.Logger;
 
 public class AuthenticationServiceImpl implements AuthenticationService {
+    private static final Logger logger = Logger.getLogger(AuthenticationServiceImpl.class);
+
     @Override
     public User login(String login, String password) throws AuthenticationException {
-        //TODO: add corresponding log message about method login was called
+        logger.info("login() called for user: " + login);
         User user = findByLogin(login);
         if (!user.getPassword().equals(password)) {
+            logger.warn("Invalid credentials for user: " + login);
             throw new AuthenticationException("Username or password are incorrect");
         }
+        logger.info("User authenticated: " + login);
         return user;
     }
 
     private User findByLogin(String login) {
         User user = new User(login, "1234");
-        // this user identifier should be set by DB. We will use dummy data for this example
-        user.setUserId(2L);
+        user.setUserId(2L); // dummy data
         return user;
     }
 }

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

@@ -4,27 +4,28 @@
 import java.util.List;
 import mate.academy.model.Order;
 import mate.academy.model.Product;
+import org.apache.log4j.Logger;
 
 public class OrderServiceImpl implements OrderService {
+    private static final Logger logger = Logger.getLogger(OrderServiceImpl.class);
+
     @Override
     public Order completeOrder(Long userId) {
-        // TODO: add log message about method completeOrder was called
+        logger.info("completeOrder() called for 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
-        // For test purpose we simplify this and return dummy data
         order.setOrderId(1L);
+        logger.info("Order created with id=" + order.getOrderId() + " for userId=" + userId);
         return order;
     }
 
     private List<Product> getAllProductsFromShoppingCart(Long userId) {
-        // NOTE: In production ready code this method should fetch data from DB
-        // For test purpose we simplify this method and return dummy data
         Product iphone = new Product("iPhone X", BigDecimal.valueOf(1199));
         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("Fetched " + products.size() + " products from shopping cart for userId="
+                + userId);
         return products;
     }
 }

src/main/java/resources/log4j.properties

@@ -0,0 +1,14 @@
+log4j.rootLogger=INFO, console, file
+
+# Console appender
+log4j.appender.console=org.apache.log4j.ConsoleAppender
+log4j.appender.console.layout=org.apache.log4j.PatternLayout
+log4j.appender.console.layout.ConversionPattern=%d{ISO8601} %-5p [%t] %c - %m%n
+
+# File appender
+log4j.appender.file=org.apache.log4j.RollingFileAppender
+log4j.appender.file.File=logs/app.log
+log4j.appender.file.MaxFileSize=5MB
+log4j.appender.file.MaxBackupIndex=3
+log4j.appender.file.layout=org.apache.log4j.PatternLayout
+log4j.appender.file.layout.ConversionPattern=%d{ISO8601} %-5p [%t] %c - %m%n