#970 single logging framework should be enforced (#982)

* #496 Add pipeline module to parent pom ✨

* #496: Add main application class and test for pipeline

* #496: Checkstyle format and add log messages on pipeline stages 🎨

* #496: Fill readme sections of pipeline ✨

* #496: Javadocs and checkstyle formatting 🎨

* #496: Follow PMD checks and add more explanation as block comment on App.java

* #496: Apply requested PR changes by iluwatar 🎨

* #970: Replace log4j usage on commander pattern to Slf4j API 🎨

* #970: Replace log4j usage on dao pattern to Slf4j API 🎨

* #970: Replace log4j usage on data mapper pattern to Slf4j API 🎨

* #970: Remove log4j dependency on data transfer object pom 🔥

* #970: Replace log4j usage on module pattern to Slf4j API 🎨

* #970: Replace log4j usage on serverless pattern to Slf4j API 🎨

This also removes the aws log4j dependency

* #970: Remove unnecessary gitignore line for log4j.xml 🔥

* #970: Remove remaining remnants of log4j 🔥

* #970: Replace System.out logging with appropriate logging methods 🎨

* #970: Replace System.out method references to Logger::info 🎨

.gitignore

@@ -16,5 +16,4 @@ datanucleus.log
 /bin/
 /bin/
 *.log
-data-mapper/src/main/resources/log4j.xml
 event-sourcing/Journal.json

collection-pipeline/src/test/java/com/iluwatar/collectionpipeline/AppTest.java

@@ -30,11 +30,14 @@ import java.util.List;
 import java.util.Map;
 
 import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Tests that Collection Pipeline methods work as expected.
  */
 public class AppTest {
+  private static final Logger LOGGER = LoggerFactory.getLogger(AppTest.class);
 
   private List<Car> cars = CarFactory.createCars();
   
@@ -61,7 +64,7 @@ public class AppTest {
         new Car("Jeep", "Comanche", 1990, Category.JEEP)));
     Map<Category, List<Car>> modelsFunctional = FunctionalProgramming.getGroupingOfCarsByCategory(cars);
     Map<Category, List<Car>> modelsImperative = ImperativeProgramming.getGroupingOfCarsByCategory(cars);
-    System.out.println("Category " + modelsFunctional);
+    LOGGER.info("Category " + modelsFunctional);
     assertEquals(modelsExpected, modelsFunctional);
     assertEquals(modelsExpected, modelsImperative);
   }

commander/pom.xml

@@ -36,10 +36,5 @@
       <artifactId>junit-jupiter-engine</artifactId>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>log4j</groupId>
-      <artifactId>log4j</artifactId>
-      <version>1.2.17</version>
-    </dependency>
   </dependencies>
 </project>

commander/properties/log4j.properties

@@ -1,41 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-
-#Define root logger options
-log4j.rootLogger=TRACE, file, console
-
-#Define console appender
-log4j.appender.console=org.apache.log4j.ConsoleAppender
-logrj.appender.console.Target=System.out
-log4j.appender.console.layout=org.apache.log4j.PatternLayout
-log4j.appender.console.layout.ConversionPattern=%d{yyyy-MM-dd} %d{HH:mm:ss} %5p[%t] %m%n
-
-#Define rolling file appender
-log4j.appender.file=org.apache.log4j.RollingFileAppender
-log4j.appender.file.File=/log/logFile.log
-log4j.appender.file.Append=true
-log4j.appender.file.ImmediateFlush=true
-log4j.appender.file.MaxFileSize=10MB
-log4j.appender.file.MaxBackupIndex=5
-log4j.appender.file.layout=org.apache.log4j.PatternLayout
-log4j.appender.file.layout.ConversionPattern=%d %d{HH:mm:ss} %5p[%t] %m%n

commander/src/main/java/com/iluwatar/commander/Commander.java

@@ -23,7 +23,6 @@
 package com.iluwatar.commander;
 
 import java.util.ArrayList;
-import org.apache.log4j.Logger;
 import com.iluwatar.commander.employeehandle.EmployeeHandle;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 import com.iluwatar.commander.exceptions.ItemUnavailableException;
@@ -37,6 +36,8 @@ import com.iluwatar.commander.queue.QueueDatabase;
 import com.iluwatar.commander.queue.QueueTask;
 import com.iluwatar.commander.queue.QueueTask.TaskType;
 import com.iluwatar.commander.shippingservice.ShippingService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  *<p>Commander pattern is used to handle all issues that can come up while making a
@@ -86,7 +87,7 @@ public class Commander {
   private final long messageTime;
   private final long employeeTime; 
   private boolean finalSiteMsgShown;
-  static final Logger LOG = Logger.getLogger(Commander.class);
+  static final Logger LOG = LoggerFactory.getLogger(Commander.class);
   //we could also have another db where it stores all orders
   
   Commander(EmployeeHandle empDb, PaymentService pService, ShippingService sService,
@@ -125,27 +126,27 @@ public class Commander {
       String transactionId = shippingService.receiveRequest(order.item, order.user.address); 
       //could save this transaction id in a db too
       LOG.info("Order " + order.id + ": Shipping placed successfully, transaction id: " + transactionId);
-      System.out.println("Order has been placed and will be shipped to you. Please wait while we make your"
+      LOG.info("Order has been placed and will be shipped to you. Please wait while we make your"
           + " payment... "); 
       sendPaymentRequest(order);       
       return; 
     };
     Retry.HandleErrorIssue<Order> handleError = (o,err) -> {
       if (ShippingNotPossibleException.class.isAssignableFrom(err.getClass())) {
-        System.out.println("Shipping is currently not possible to your address. We are working on the problem "
+        LOG.info("Shipping is currently not possible to your address. We are working on the problem "
             + "and will get back to you asap.");
         finalSiteMsgShown = true;
         LOG.info("Order " + order.id + ": Shipping not possible to address, trying to add problem to employee db..");
         employeeHandleIssue(o);
       } else if (ItemUnavailableException.class.isAssignableFrom(err.getClass())) {
-        System.out.println("This item is currently unavailable. We will inform you as soon as the item becomes "
+        LOG.info("This item is currently unavailable. We will inform you as soon as the item becomes "
             + "available again.");
         finalSiteMsgShown = true;
         LOG.info("Order " + order.id + ": Item " + order.item + " unavailable, trying to add problem to employee "
             + "handle..");
         employeeHandleIssue(o);
       } else {
-        System.out.println("Sorry, there was a problem in creating your order. Please try later.");
+        LOG.info("Sorry, there was a problem in creating your order. Please try later.");
         LOG.error("Order " + order.id + ": Shipping service unavailable, order not placed..");
         finalSiteMsgShown = true;
       }
@@ -183,7 +184,7 @@ public class Commander {
             order.paid = PaymentStatus.Done; 
             LOG.info("Order " + order.id + ": Payment successful, transaction Id: " + transactionId);
             if (!finalSiteMsgShown) { 
-              System.out.println("Payment made successfully, thank you for shopping with us!!"); 
+              LOG.info("Payment made successfully, thank you for shopping with us!!"); 
               finalSiteMsgShown = true; 
             } 
             sendSuccessMessage(order); 
@@ -193,7 +194,7 @@ public class Commander {
         Retry.HandleErrorIssue<Order> handleError = (o,err) -> {
           if (PaymentDetailsErrorException.class.isAssignableFrom(err.getClass())) {
             if (!finalSiteMsgShown) {
-              System.out.println("There was an error in payment. Your account/card details may have been incorrect. "
+              LOG.info("There was an error in payment. Your account/card details may have been incorrect. "
                   + "Meanwhile, your order has been converted to COD and will be shipped.");
               finalSiteMsgShown = true;
             }
@@ -204,7 +205,7 @@ public class Commander {
             try {
               if (o.messageSent.equals(MessageSent.NoneSent)) {
                 if (!finalSiteMsgShown) {
-                  System.out.println("There was an error in payment. We are on it, and will get back to you "
+                  LOG.info("There was an error in payment. We are on it, and will get back to you "
                       + "asap. Don't worry, your order has been placed and will be shipped.");
                   finalSiteMsgShown = true;
                 }

commander/src/main/java/com/iluwatar/commander/messagingservice/MessagingService.java

@@ -24,6 +24,8 @@ package com.iluwatar.commander.messagingservice;
 
 import com.iluwatar.commander.Service;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * The MessagingService is used to send messages to user regarding their order and 
@@ -32,6 +34,7 @@ import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
  */
 
 public class MessagingService extends Service {
+  private static final Logger LOGGER = LoggerFactory.getLogger(MessagingService.class);
 
   enum MessageToSend {
     PaymentFail, PaymentTrying, PaymentSuccessful
@@ -74,7 +77,7 @@ public class MessagingService extends Service {
     MessageRequest req = (MessageRequest) parameters[0];
     if (this.database.get(req.reqId) == null) { //idempotence, in case db fails here
       database.add(req); //if successful:
-      System.out.println(sendMessage(req.msg));
+      LOGGER.info(sendMessage(req.msg));
       return req.reqId;
     }
     return null;

converter/src/main/java/com/iluwatar/converter/App.java

@@ -24,6 +24,8 @@ package com.iluwatar.converter;
 
 
 import com.google.common.collect.Lists;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -35,6 +37,8 @@ import java.util.List;
  * objects between types.
  */
 public class App {
+  
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
   /**
    * Program entry point
    *
@@ -45,16 +49,16 @@ public class App {
 
     UserDto dtoUser = new UserDto("John", "Doe", true, "whatever[at]wherever.com");
     User user = userConverter.convertFromDto(dtoUser);
-    System.out.println("Entity converted from DTO:" + user);
+    LOGGER.info("Entity converted from DTO:" + user);
 
     ArrayList<User> users = Lists.newArrayList(new User("Camile", "Tough", false, "124sad"),
         new User("Marti", "Luther", true, "42309fd"), new User("Kate", "Smith", true, "if0243"));
-    System.out.println("Domain entities:");
+    LOGGER.info("Domain entities:");
-    users.forEach(System.out::println);
+    users.stream().map(User::toString).forEach(LOGGER::info);
 
-    System.out.println("DTO entities converted from domain:");
+    LOGGER.info("DTO entities converted from domain:");
     List<UserDto> dtoEntities = userConverter.createFromEntities(users);
-    dtoEntities.forEach(System.out::println);
+    dtoEntities.stream().map(UserDto::toString).forEach(LOGGER::info);
 
   }
 }

dao/pom.xml

@@ -40,10 +40,6 @@
       <artifactId>junit-jupiter-engine</artifactId>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>log4j</groupId>
-      <artifactId>log4j</artifactId>
-    </dependency>
     <dependency>
         <groupId>com.h2database</groupId>
         <artifactId>h2</artifactId>
@@ -53,49 +49,4 @@
         <artifactId>mockito-core</artifactId>
     </dependency>
   </dependencies>
-
-  <build>
-
-    <!-- 
-    log4j.xml file will be copied both in ${project.build.outputDirectory} 
-    and ${project.build.directory}. Thanks to Sean Patrick Floyd 
-    (http://stackoverflow.com/questions/5637532/maven-how-to-place-resource-file-together-with-jar) 
-    -->
-      
-    <resources>
-      <resource> <!-- regular processing for every resource file -->
-        <directory>src/main/resources</directory>
-      </resource>
-      <resource> <!-- processing with a different output directory for log4j.xml -->
-        <directory>src/main/resources</directory>
-        <includes>
-          <include>log4j.xml</include>
-        </includes>
-        <targetPath>..</targetPath> <!-- relative to target/classes i.e. ${project.build.directory} -->
-      </resource>
-    </resources>
-
-    <plugins>
-
-      <!-- 
-      This will exclude log4j.xml file from generated JAR 
-      -->
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-jar-plugin</artifactId>
-        <version>2.6</version>
-        <configuration>
-          <excludes>
-            <exclude>log4j.xml</exclude>
-          </excludes>
-          <archive>
-            <manifest>
-              <addClasspath>true</addClasspath>
-            </manifest>
-          </archive>
-        </configuration>
-      </plugin>
-
-    </plugins>
-  </build>
 </project>

dao/src/main/java/com/iluwatar/dao/App.java

@@ -31,8 +31,9 @@ import java.util.stream.Stream;
 
 import javax.sql.DataSource;
 
-import org.apache.log4j.Logger;
 import org.h2.jdbcx.JdbcDataSource;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Data Access Object (DAO) is an object that provides an abstract interface to some type of
@@ -50,7 +51,7 @@ import org.h2.jdbcx.JdbcDataSource;
  */
 public class App {
   private static final String DB_URL = "jdbc:h2:~/dao";
-  private static Logger log = Logger.getLogger(App.class);
+  private static Logger log = LoggerFactory.getLogger(App.class);
   private static final String ALL_CUSTOMERS = "customerDao.getAllCustomers(): ";
   
   /**
@@ -94,7 +95,7 @@ public class App {
     addCustomers(customerDao);
     log.info(ALL_CUSTOMERS);
     try (Stream<Customer> customerStream = customerDao.getAll()) {
-      customerStream.forEach((customer) -> log.info(customer));
+      customerStream.forEach((customer) -> log.info(customer.toString()));
     }
     log.info("customerDao.getCustomerById(2): " + customerDao.getById(2));
     final Customer customer = new Customer(4, "Dan", "Danson");
@@ -105,7 +106,7 @@ public class App {
     customerDao.update(customer);
     log.info(ALL_CUSTOMERS);
     try (Stream<Customer> customerStream = customerDao.getAll()) {
-      customerStream.forEach((cust) -> log.info(cust));
+      customerStream.forEach((cust) -> log.info(cust.toString()));
     }
     customerDao.delete(customer);
     log.info(ALL_CUSTOMERS + customerDao.getAll());

dao/src/main/java/com/iluwatar/dao/DbCustomerDao.java

@@ -22,6 +22,9 @@
  */
 package com.iluwatar.dao;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
@@ -35,15 +38,13 @@ import java.util.stream.StreamSupport;
 
 import javax.sql.DataSource;
 
-import org.apache.log4j.Logger;
-
 /**
  * An implementation of {@link CustomerDao} that persists customers in RDBMS.
  *
  */
 public class DbCustomerDao implements CustomerDao {
 
-  private static final Logger LOGGER = Logger.getLogger(DbCustomerDao.class);
+  private static final Logger LOGGER = LoggerFactory.getLogger(DbCustomerDao.class);
 
   private final DataSource dataSource;
 

dao/src/main/resources/log4j.xml

@@ -1,41 +0,0 @@
-<?xml version="1.0" encoding="UTF-8" ?>
-<!--
-
-    The MIT License
-    Copyright © 2014-2019 Ilkka Seppälä
-
-    Permission is hereby granted, free of charge, to any person obtaining a copy
-    of this software and associated documentation files (the "Software"), to deal
-    in the Software without restriction, including without limitation the rights
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-    copies of the Software, and to permit persons to whom the Software is
-    furnished to do so, subject to the following conditions:
-
-    The above copyright notice and this permission notice shall be included in
-    all copies or substantial portions of the Software.
-
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-    THE SOFTWARE.
-
--->
-<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
-<log4j:configuration debug="true"
-  xmlns:log4j='http://jakarta.apache.org/log4j/'>
-
-  <appender name="console" class="org.apache.log4j.ConsoleAppender">
-    <layout class="org.apache.log4j.PatternLayout">
-      <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
-    </layout>
-  </appender>
-
-  <root>
-    <level value="INFO" />
-    <appender-ref ref="console" />
-  </root>
-
-</log4j:configuration>

data-mapper/pom.xml

@@ -37,9 +37,5 @@
 			<artifactId>junit-jupiter-engine</artifactId>
 			<scope>test</scope>
 		</dependency>
-		<dependency>
-			<groupId>log4j</groupId>
-			<artifactId>log4j</artifactId>
-		</dependency>
 	</dependencies>
 </project>

data-mapper/src/main/java/com/iluwatar/datamapper/App.java

@@ -22,9 +22,10 @@
  */
 package com.iluwatar.datamapper;
 
-import java.util.Optional;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
-import org.apache.log4j.Logger;
+import java.util.Optional;
 
 /**
  * The Data Mapper (DM) is a layer of software that separates the in-memory objects from the
@@ -39,7 +40,7 @@ import org.apache.log4j.Logger;
  */
 public final class App {
 
-  private static Logger log = Logger.getLogger(App.class);
+  private static Logger log = LoggerFactory.getLogger(App.class);
   private static final String STUDENT_STRING = "App.main(), student : ";
   
 

data-mapper/src/main/resources/log4j.xml

@@ -1,41 +0,0 @@
-<?xml version="1.0" encoding="UTF-8" ?>
-<!--
-
-    The MIT License
-    Copyright © 2014-2019 Ilkka Seppälä
-
-    Permission is hereby granted, free of charge, to any person obtaining a copy
-    of this software and associated documentation files (the "Software"), to deal
-    in the Software without restriction, including without limitation the rights
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-    copies of the Software, and to permit persons to whom the Software is
-    furnished to do so, subject to the following conditions:
-
-    The above copyright notice and this permission notice shall be included in
-    all copies or substantial portions of the Software.
-
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-    THE SOFTWARE.
-
--->
-<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
-<log4j:configuration debug="true"
-  xmlns:log4j='http://jakarta.apache.org/log4j/'>
-
-  <appender name="console" class="org.apache.log4j.ConsoleAppender">
-    <layout class="org.apache.log4j.PatternLayout">
-      <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
-    </layout>
-  </appender>
-
-  <root>
-    <level value="INFO" />
-    <appender-ref ref="console" />
-  </root>
-
-</log4j:configuration>

data-transfer-object/pom.xml

@@ -37,9 +37,5 @@
             <artifactId>junit-jupiter-engine</artifactId>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>log4j</groupId>
-            <artifactId>log4j</artifactId>
-        </dependency>
     </dependencies>
 </project>

dirty-flag/src/main/java/com/iluwatar/dirtyflag/App.java

@@ -22,6 +22,9 @@
  */
 package com.iluwatar.dirtyflag;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.List;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
@@ -48,6 +51,8 @@ import java.util.concurrent.TimeUnit;
  * when needed. {@link World} mainly serves the data to the front-end.
  */
 public class App {
+  
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
   /**
    * Program execution point
    */
@@ -59,9 +64,9 @@ public class App {
       @Override
       public void run() {
         List<String> countries = world.fetch();
-        System.out.println("Our world currently has the following countries:-");
+        LOGGER.info("Our world currently has the following countries:-");
         for (String country : countries) {
-          System.out.println("\t" + country);
+          LOGGER.info("\t" + country);
         }
       }
     }, 0, 15, TimeUnit.SECONDS); // Run at every 15 seconds.

dirty-flag/src/main/java/com/iluwatar/dirtyflag/DataFetcher.java

@@ -22,6 +22,10 @@
  */
 package com.iluwatar.dirtyflag;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.xml.crypto.Data;
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileReader;
@@ -37,6 +41,8 @@ import java.util.List;
  */
 public class DataFetcher {
 
+  private static final Logger LOGGER = LoggerFactory.getLogger(DataFetcher.class);
+
   private final String filename = "world.txt";
   private long lastFetched;
 
@@ -62,7 +68,7 @@ public class DataFetcher {
     File file = new File(classLoader.getResource(filename).getFile());
 
     if (isDirty(file.lastModified())) {
-      System.out.println(filename + " is dirty! Re-fetching file content...");
+      LOGGER.info(filename + " is dirty! Re-fetching file content...");
 
       List<String> data = new ArrayList<String>();
       try (BufferedReader br = new BufferedReader(new FileReader(file))) {

event-queue/src/main/java/com/iluwatar/event/queue/App.java

@@ -22,6 +22,9 @@
  */
 package com.iluwatar.event.queue;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
@@ -39,6 +42,8 @@ import javax.sound.sampled.UnsupportedAudioFileException;
  * items from the queue at a later time.
  */
 public class App {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
   /**
    * Program entry point.
    * 
@@ -51,7 +56,7 @@ public class App {
     audio.playSound(audio.getAudioStream("./etc/Bass-Drum-1.wav"), -10.0f);
     audio.playSound(audio.getAudioStream("./etc/Closed-Hi-Hat-1.wav"), -8.0f);
     
-    System.out.println("Press Enter key to stop the program...");
+    LOGGER.info("Press Enter key to stop the program...");
     try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
       br.read();
     }

hexagonal/src/main/java/com/iluwatar/hexagonal/administration/ConsoleAdministration.java

@@ -81,7 +81,7 @@ public class ConsoleAdministration {
   }
 
   private static String readString(Scanner scanner) {
-    System.out.print("> ");
+    LOGGER.info("> ");
     return scanner.next();
   }
 }

hexagonal/src/main/java/com/iluwatar/hexagonal/service/ConsoleLottery.java

@@ -82,7 +82,7 @@ public class ConsoleLottery {
   }
 
   private static String readString(Scanner scanner) {
-    System.out.print("> ");
+    LOGGER.info("> ");
     return scanner.next();
   }
 }

hexagonal/src/main/java/com/iluwatar/hexagonal/service/LotteryConsoleServiceImpl.java

@@ -122,7 +122,7 @@ public class LotteryConsoleServiceImpl implements LotteryConsoleService {
   }
 
   private String readString(Scanner scanner) {
-    System.out.print( "> " );
+    logger.info( "> " );
     return scanner.next();
   }
 }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/App.java

@@ -23,6 +23,8 @@
 package com.iluwatar.masterworker;
 
 import com.iluwatar.masterworker.system.ArrayTransposeMasterWorker;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * <p>The <b><em>Master-Worker</em></b> pattern is used when the problem at hand can be solved by dividing into 
@@ -46,6 +48,7 @@ import com.iluwatar.masterworker.system.ArrayTransposeMasterWorker;
 
 public class App {
 
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
   /**
    * Program entry point.
    * @param args command line args
@@ -60,10 +63,9 @@ public class App {
     ArrayResult result = (ArrayResult) mw.getResult(input);    
     if (result != null) {
       ArrayUtilityMethods.printMatrix(inputMatrix);
-      System.out.println("");
       ArrayUtilityMethods.printMatrix(result.data);
     } else {
-      System.out.println("Please enter non-zero input");
+      LOGGER.info("Please enter non-zero input");
     }
   }
 

master-worker-pattern/src/main/java/com/iluwatar/masterworker/ArrayUtilityMethods.java

@@ -22,6 +22,9 @@
  */
 package com.iluwatar.masterworker;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.Random;
 
 /**
@@ -30,6 +33,7 @@ import java.util.Random;
 
 public class ArrayUtilityMethods {
 
+  private static final Logger LOGGER = LoggerFactory.getLogger(ArrayUtilityMethods.class);
   /**
    * Method arraysSame compares 2 arrays @param a1 and @param a2
    * and @return whether their values are equal (boolean).
@@ -100,9 +104,9 @@ public class ArrayUtilityMethods {
     //prints out int[][]
     for (int i = 0; i < matrix.length; i++) {
       for (int j = 0; j < matrix[0].length; j++) {
-        System.out.print(matrix[i][j] + " ");
+        LOGGER.info(matrix[i][j] + " ");
       }
-      System.out.println("");
+      LOGGER.info("");
     }
   }
   

module/pom.xml

@@ -37,9 +37,5 @@
 			<artifactId>junit-jupiter-engine</artifactId>
 			<scope>test</scope>
 		</dependency>
-		<dependency>
-			<groupId>log4j</groupId>
-			<artifactId>log4j</artifactId>
-		</dependency>
 	</dependencies>
 </project>

module/src/main/java/com/iluwatar/module/ConsoleLoggerModule.java

@@ -22,9 +22,10 @@
  */
 package com.iluwatar.module;
 
-import java.io.PrintStream;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
-import org.apache.log4j.Logger;
+import java.io.PrintStream;
 
 /**
  * The ConsoleLoggerModule is responsible for showing logs on System Console
@@ -34,7 +35,7 @@ import org.apache.log4j.Logger;
  */
 public final class ConsoleLoggerModule {
 
-  private static final Logger LOGGER = Logger.getLogger(ConsoleLoggerModule.class);
+  private static final Logger LOGGER = LoggerFactory.getLogger(ConsoleLoggerModule.class);
 
   private static ConsoleLoggerModule singleton = null;
 

module/src/main/java/com/iluwatar/module/FileLoggerModule.java

@@ -22,12 +22,13 @@
  */
 package com.iluwatar.module;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.PrintStream;
 
-import org.apache.log4j.Logger;
-
 /**
  * The FileLoggerModule is responsible for showing logs on File System
  * <p>
@@ -36,7 +37,7 @@ import org.apache.log4j.Logger;
  */
 public final class FileLoggerModule {
 
-  private static final Logger LOGGER = Logger.getLogger(FileLoggerModule.class);
+  private static final Logger LOGGER = LoggerFactory.getLogger(FileLoggerModule.class);
 
   private static FileLoggerModule singleton = null;
 

module/src/main/resources/log4j.xml

@@ -1,41 +0,0 @@
-<?xml version="1.0" encoding="UTF-8" ?>
-<!--
-
-    The MIT License
-    Copyright © 2014-2019 Ilkka Seppälä
-
-    Permission is hereby granted, free of charge, to any person obtaining a copy
-    of this software and associated documentation files (the "Software"), to deal
-    in the Software without restriction, including without limitation the rights
-    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-    copies of the Software, and to permit persons to whom the Software is
-    furnished to do so, subject to the following conditions:
-
-    The above copyright notice and this permission notice shall be included in
-    all copies or substantial portions of the Software.
-
-    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-    THE SOFTWARE.
-
--->
-<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
-<log4j:configuration debug="true"
-  xmlns:log4j='http://jakarta.apache.org/log4j/'>
-
-  <appender name="console" class="org.apache.log4j.ConsoleAppender">
-    <layout class="org.apache.log4j.PatternLayout">
-      <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
-    </layout>
-  </appender>
-
-  <root>
-    <level value="INFO" />
-    <appender-ref ref="console" />
-  </root>
-
-</log4j:configuration>

module/src/test/java/com/iluwatar/module/FileLoggerModuleTest.java

@@ -22,8 +22,9 @@
  */
 package com.iluwatar.module;
 
-import org.apache.log4j.Logger;
 import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.BufferedReader;
 import java.io.FileNotFoundException;
@@ -45,7 +46,7 @@ import static org.junit.jupiter.api.Assertions.assertNull;
  */
 public final class FileLoggerModuleTest {
 
-  private static final Logger LOGGER = Logger.getLogger(FileLoggerModuleTest.class);
+  private static final Logger LOGGER = LoggerFactory.getLogger(FileLoggerModuleTest.class);
 
   private static final String OUTPUT_FILE = "output.txt";
   private static final String ERROR_FILE = "error.txt";

naked-objects/dom/exclude-pmd.properties

@@ -1,24 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-
-domainapp.dom.modules.simple.QSimpleObject=UnusedFormalParameter

naked-objects/dom/pom.xml

@@ -143,7 +143,6 @@
 						<version>${datanucleus-maven-plugin.version}</version>
 						<configuration>
 							<fork>false</fork>
-							<log4jConfiguration>${basedir}/log4j.properties</log4jConfiguration>
 							<verbose>true</verbose>
 							<props>${basedir}/datanucleus.properties</props>
 						</configuration>

naked-objects/integtests/src/test/java/domainapp/integtests/bootstrap/SimpleAppSystemInitializer.java

@@ -49,7 +49,6 @@ public final class SimpleAppSystemInitializer {
   private static class SimpleAppSystemBuilder extends IsisSystemForTest.Builder {
 
     public SimpleAppSystemBuilder() {
-      withLoggingAt(org.apache.log4j.Level.INFO);
       with(testConfiguration());
       with(new DataNucleusPersistenceMechanismInstaller());
 

naked-objects/integtests/src/test/java/domainapp/integtests/specglue/BootstrappingGlue.java

@@ -36,7 +36,6 @@ public class BootstrappingGlue extends CukeGlueAbstract {
 
   @Before(value = {"@integration"}, order = 100)
   public void beforeScenarioIntegrationScope() {
-    org.apache.log4j.PropertyConfigurator.configure("logging.properties");
     SimpleAppSystemInitializer.initIsft();
 
     before(ScenarioExecutionScope.INTEGRATION);

naked-objects/integtests/src/test/java/domainapp/integtests/tests/SimpleAppIntegTest.java

@@ -36,7 +36,6 @@ public abstract class SimpleAppIntegTest extends IntegrationTestAbstract {
 
   @BeforeClass
   public static void initClass() {
-    org.apache.log4j.PropertyConfigurator.configure("logging.properties");
     SimpleAppSystemInitializer.initIsft();
 
     // instantiating will install onto ThreadLocal

naked-objects/webapp/pom.xml

@@ -216,26 +216,6 @@
 			<artifactId>hsqldb</artifactId>
 		</dependency>
 
-		<!-- <dependency> <groupId>postgresql</groupId> <artifactId>postgresql</artifactId> 
-			<version>9.1-901.jdbc4</version> </dependency> -->
-
-		<!-- mvn install:install-file -Dfile=sqljdbc4.jar \ -DgroupId=com.microsoft.sqlserver 
-			\ -DartifactId=jdbc \ -Dversion=4.0 \ -Dpackaging=jar -->
-		<!-- <dependency> <groupId>com.microsoft.sqlserver</groupId> <artifactId>sqljdbc4</artifactId> 
-			<version>4.0</version> </dependency> -->
-
-		<dependency>
-			<groupId>org.lazyluke</groupId>
-			<artifactId>log4jdbc-remix</artifactId>
-			<exclusions>
-				<exclusion>
-					<groupId>org.slf4j</groupId>
-					<artifactId>slf4j-api</artifactId>
-				</exclusion>
-			</exclusions>
-		</dependency>
-
-
 		<dependency>
 			<groupId>junit</groupId>
 			<artifactId>junit</artifactId>

naked-objects/webapp/src/main/java/domainapp/webapp/SimpleApplication.java

@@ -50,6 +50,8 @@ import de.agilecoders.wicket.core.Bootstrap;
 import de.agilecoders.wicket.core.settings.IBootstrapSettings;
 import de.agilecoders.wicket.themes.markup.html.bootswatch.BootswatchTheme;
 import de.agilecoders.wicket.themes.markup.html.bootswatch.BootswatchThemeProvider;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 
 /**
@@ -72,6 +74,7 @@ import de.agilecoders.wicket.themes.markup.html.bootswatch.BootswatchThemeProvid
  */
 public class SimpleApplication extends IsisWicketApplication {
 
+  private static final Logger LOGGER = LoggerFactory.getLogger(SimpleApplication.class);
   private static final long serialVersionUID = 1L;
 
   /**
@@ -124,7 +127,7 @@ public class SimpleApplication extends IsisWicketApplication {
         servletRequest.getSession().invalidate();
       }
     } catch (Exception e) {
-      System.out.println(e);
+      LOGGER.error(e.getMessage());
     }
     return super.newWebRequest(servletRequest, filterPath);
   }

pipeline/src/main/java/com.iluwatar.pipeline/ConvertToCharArrayHandler.java

@@ -32,12 +32,12 @@ import java.util.Arrays;
  */
 class ConvertToCharArrayHandler implements Handler<String, char[]> {
 
-  private final Logger logger = LoggerFactory.getLogger(ConvertToCharArrayHandler.class);
+  private static final Logger LOGGER = LoggerFactory.getLogger(ConvertToCharArrayHandler.class);
 
   @Override
   public char[] process(String input) {
     char[] characters = input.toCharArray();
-    logger.info(String.format("Current handler: %s, input is %s of type %s, output is %s, of type %s",
+    LOGGER.info(String.format("Current handler: %s, input is %s of type %s, output is %s, of type %s",
         ConvertToCharArrayHandler.class, input, String.class, Arrays.toString(characters), Character[].class));
 
     return characters;

pipeline/src/main/java/com.iluwatar.pipeline/RemoveAlphabetsHandler.java

@@ -30,7 +30,7 @@ import org.slf4j.LoggerFactory;
  */
 class RemoveAlphabetsHandler implements Handler<String, String> {
 
-  private final Logger logger = LoggerFactory.getLogger(RemoveAlphabetsHandler.class);
+  private static final Logger LOGGER = LoggerFactory.getLogger(RemoveAlphabetsHandler.class);
 
   @Override
   public String process(String input) {
@@ -46,7 +46,7 @@ class RemoveAlphabetsHandler implements Handler<String, String> {
     }
 
     String inputWithoutAlphabetsStr = inputWithoutAlphabets.toString();
-    logger.info(String.format("Current handler: %s, input is %s of type %s, output is %s, of type %s",
+    LOGGER.info(String.format("Current handler: %s, input is %s of type %s, output is %s, of type %s",
         RemoveAlphabetsHandler.class, input, String.class, inputWithoutAlphabetsStr, String.class));
 
     return inputWithoutAlphabetsStr;

pipeline/src/main/java/com.iluwatar.pipeline/RemoveDigitsHandler.java

@@ -30,7 +30,7 @@ import org.slf4j.LoggerFactory;
  */
 class RemoveDigitsHandler implements Handler<String, String> {
 
-  private final Logger logger = LoggerFactory.getLogger(RemoveDigitsHandler.class);
+  private static final Logger LOGGER = LoggerFactory.getLogger(RemoveDigitsHandler.class);
 
   @Override
   public String process(String input) {
@@ -46,7 +46,7 @@ class RemoveDigitsHandler implements Handler<String, String> {
     }
 
     String inputWithoutDigitsStr = inputWithoutDigits.toString();
-    logger.info(String.format("Current handler: %s, input is %s of type %s, output is %s, of type %s",
+    LOGGER.info(String.format("Current handler: %s, input is %s of type %s, output is %s, of type %s",
         RemoveDigitsHandler.class, input, String.class, inputWithoutDigitsStr, String.class));
 
     return inputWithoutDigitsStr;

pom.xml

@@ -56,10 +56,8 @@
         <logback.version>1.2.3</logback.version>
         <aws-lambda-core.version>1.1.0</aws-lambda-core.version>
         <aws-java-sdk-dynamodb.version>1.11.289</aws-java-sdk-dynamodb.version>
-        <aws-lambda-log4j.version>1.0.0</aws-lambda-log4j.version>
         <aws-lambda-java-events.version>2.0.1</aws-lambda-java-events.version>
         <jackson.version>2.8.5</jackson.version>
-        <log4j.version>1.2.17</log4j.version>
         <jaxb-api.version>2.3.1</jaxb-api.version>
         <jaxb-impl.version>2.3.2</jaxb-impl.version>
         <annotation-api.version>1.3.2</annotation-api.version>
@@ -304,11 +302,6 @@
                 <artifactId>mongo-java-driver</artifactId>
                 <version>${mongo-java-driver.version}</version>
             </dependency>
-            <dependency>
-                <groupId>log4j</groupId>
-                <artifactId>log4j</artifactId>
-                <version>${log4j.version}</version>
-            </dependency>
             <dependency>
                 <groupId>javax.xml.bind</groupId>
                 <artifactId>jaxb-api</artifactId>

serverless/pom.xml

@@ -60,11 +60,6 @@
             <artifactId>aws-lambda-java-events</artifactId>
             <version>${aws-lambda-java-events.version}</version>
         </dependency>
-        <dependency>
-            <groupId>com.amazonaws</groupId>
-            <artifactId>aws-lambda-java-log4j</artifactId>
-            <version>${aws-lambda-log4j.version}</version>
-        </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-core</artifactId>

serverless/src/main/java/com/iluwatar/serverless/baas/api/FindPersonApiHandler.java

@@ -27,7 +27,10 @@ import com.amazonaws.services.lambda.runtime.RequestHandler;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
 import com.iluwatar.serverless.baas.model.Person;
-import org.apache.log4j.Logger;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Map;
 
 /**
  * find person from persons collection
@@ -36,13 +39,15 @@ import org.apache.log4j.Logger;
 public class FindPersonApiHandler extends AbstractDynamoDbHandler<Person>
     implements RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent> {
 
-  private static final Logger LOG = Logger.getLogger(FindPersonApiHandler.class);
+  private static final Logger LOG = LoggerFactory.getLogger(FindPersonApiHandler.class);
   private static final Integer SUCCESS_STATUS_CODE = 200;
 
   @Override
   public APIGatewayProxyResponseEvent handleRequest(APIGatewayProxyRequestEvent apiGatewayProxyRequestEvent,
                                                     Context context) {
-    LOG.info(apiGatewayProxyRequestEvent.getPathParameters());
+    Map<String, String> pathParameters = apiGatewayProxyRequestEvent.getPathParameters();
+    pathParameters.keySet().stream().map(key -> key + "=" + pathParameters.get(key)).forEach(LOG::info);
+
     Person person = this.getDynamoDbMapper().load(Person.class, apiGatewayProxyRequestEvent
         .getPathParameters().get("id"));
 

serverless/src/main/java/com/iluwatar/serverless/baas/api/SavePersonApiHandler.java

@@ -27,7 +27,8 @@ import com.amazonaws.services.lambda.runtime.RequestHandler;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
 import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
 import com.iluwatar.serverless.baas.model.Person;
-import org.apache.log4j.Logger;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
 
@@ -38,7 +39,7 @@ import java.io.IOException;
 public class SavePersonApiHandler extends AbstractDynamoDbHandler<Person>
     implements RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent> {
 
-  private static final Logger LOG = Logger.getLogger(SavePersonApiHandler.class);
+  private static final Logger LOG = LoggerFactory.getLogger(SavePersonApiHandler.class);
   private static final Integer CREATED_STATUS_CODE = 201;
   private static final Integer BAD_REQUEST_STATUS_CODE = 400;
 

serverless/src/main/java/com/iluwatar/serverless/faas/api/LambdaInfoApiHandler.java

@@ -27,8 +27,8 @@ import com.iluwatar.serverless.faas.ApiGatewayResponse;
 import com.amazonaws.services.lambda.runtime.Context;
 import com.amazonaws.services.lambda.runtime.RequestHandler;
 import com.iluwatar.serverless.faas.LambdaInfo;
-import org.apache.log4j.BasicConfigurator;
+import org.slf4j.Logger;
-import org.apache.log4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -39,13 +39,12 @@ import java.util.Map;
  */
 public class LambdaInfoApiHandler implements RequestHandler<Map<String, Object>, ApiGatewayResponse> {
 
-  private static final Logger LOG = Logger.getLogger(LambdaInfoApiHandler.class);
+  private static final Logger LOG = LoggerFactory.getLogger(LambdaInfoApiHandler.class);
   private static final Integer SUCCESS_STATUS_CODE = 200;
 
 
   @Override
   public ApiGatewayResponse handleRequest(Map<String, Object> input, Context context) {
-    BasicConfigurator.configure();
     LOG.info("received: " + input);
 
     return new ApiGatewayResponse

serverless/src/main/resources/log4j.properties

@@ -1,29 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-
-log = .
-log4j.rootLogger = DEBUG, LAMBDA
-
-log4j.appender.LAMBDA=com.amazonaws.services.lambda.runtime.log4j.LambdaAppender
-log4j.appender.LAMBDA.layout=org.apache.log4j.PatternLayout
-log4j.appender.LAMBDA.layout.conversionPattern=%d{yyyy-MM-dd HH:mm:ss} <%X{AWSRequestId}> %-5p %c:%L - %m%n

spatial-partition/src/main/java/com/iluwatar/spatialpartition/App.java

@@ -22,6 +22,9 @@
  */
 package com.iluwatar.spatialpartition;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.Hashtable;
@@ -52,6 +55,7 @@ import java.util.Random;
  */
 
 public class App {
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
 
   static void noSpatialPartition(int height, int width, 
         int numOfMovements, Hashtable<Integer, Bubble> bubbles) {
@@ -73,7 +77,7 @@ public class App {
     }
     for (Integer key : bubbles.keySet()) {
       //bubbles not popped
-      System.out.println("Bubble " + key + " not popped");
+      LOGGER.info("Bubble " + key + " not popped");
     }
   }
 
@@ -101,7 +105,7 @@ public class App {
     }
     for (Integer key : bubbles.keySet()) {
       //bubbles not popped
-      System.out.println("Bubble " + key + " not popped");
+      LOGGER.info("Bubble " + key + " not popped");
     }
   }
   
@@ -119,7 +123,7 @@ public class App {
       Bubble b = new Bubble(rand.nextInt(300), rand.nextInt(300), i, rand.nextInt(2) + 1);
       bubbles1.put(i, b);
       bubbles2.put(i, b);
-      System.out.println("Bubble " + i + " with radius " + b.radius + " added at (" + b.x + "," + b.y + ")");
+      LOGGER.info("Bubble " + i + " with radius " + b.radius + " added at (" + b.x + "," + b.y + ")");
     }
 
     long start1 = System.currentTimeMillis();
@@ -128,8 +132,8 @@ public class App {
     long start2 = System.currentTimeMillis();
     App.withSpatialPartition(300,300,20,bubbles2);
     long end2 = System.currentTimeMillis();
-    System.out.println("Without spatial partition takes " + (end1 - start1) + "ms");
+    LOGGER.info("Without spatial partition takes " + (end1 - start1) + "ms");
-    System.out.println("With spatial partition takes " + (end2 - start2) + "ms");
+    LOGGER.info("With spatial partition takes " + (end2 - start2) + "ms");
   }
 }
 

spatial-partition/src/main/java/com/iluwatar/spatialpartition/Bubble.java

@@ -22,6 +22,9 @@
  */
 package com.iluwatar.spatialpartition;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.ArrayList;
 import java.util.Hashtable;
 import java.util.Random;
@@ -32,6 +35,7 @@ import java.util.Random;
  */
 
 public class Bubble extends Point<Bubble> {
+  private static final Logger LOGGER = LoggerFactory.getLogger(Bubble.class);
 
   final int radius;
 
@@ -54,7 +58,7 @@ public class Bubble extends Point<Bubble> {
   }
 
   void pop(Hashtable<Integer, Bubble> allBubbles) {
-    System.out.println("Bubble " + this.id + " popped at (" + this.x + "," + this.y + ")!");
+    LOGGER.info("Bubble " + this.id + " popped at (" + this.x + "," + this.y + ")!");
     allBubbles.remove(this.id);
   }
 

tls/src/main/java/com/iluwatar/tls/App.java

@@ -22,6 +22,9 @@
  */
 package com.iluwatar.tls;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.Calendar;
 import java.util.Date;
 import java.util.concurrent.ExecutorService;
@@ -64,6 +67,8 @@ import java.util.concurrent.Future;
  * @author Thomas Bauer, 2017 
  */
 public class App {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
   /**
    * Program entry point
    * 
@@ -99,11 +104,11 @@ public class App {
 
       // a correct run should deliver 20 times 15.12.2015
       // and a correct run shouldn't deliver any exception
-      System.out.println("The List dateList contains " + counterDateValues + " date values");
+      LOGGER.info("The List dateList contains " + counterDateValues + " date values");
-      System.out.println("The List exceptionList contains " + counterExceptions + " exceptions");
+      LOGGER.info("The List exceptionList contains " + counterExceptions + " exceptions");
 
     } catch (Exception e) {
-      System.out.println("Abnormal end of program. Program throws exception: " + e); 
+      LOGGER.info("Abnormal end of program. Program throws exception: " + e);
     }
     executor.shutdown();
   }
@@ -121,7 +126,7 @@ public class App {
       Calendar cal = Calendar.getInstance();
       cal.setTime(dt);
       // Formatted output of the date value: DD.MM.YYYY
-      System.out.println(
+      LOGGER.info(
           cal.get(Calendar.DAY_OF_MONTH) + "." + cal.get(Calendar.MONTH) + "." + +cal.get(Calendar.YEAR));
     }
     return counter;
@@ -138,7 +143,7 @@ public class App {
     int counter = 0;
     for (String ex : res.getExceptionList()) {
       counter++;
-      System.out.println(ex);
+      LOGGER.info(ex);
     }
     return counter;
   }

tls/src/main/java/com/iluwatar/tls/DateFormatCallable.java

@@ -22,6 +22,9 @@
  */
 package com.iluwatar.tls;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.util.concurrent.Callable;
@@ -40,6 +43,8 @@ import java.util.concurrent.Callable;
  * @author Thomas Bauer, 2017 
  */
 public class DateFormatCallable implements Callable<Result> {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(DateFormatCallable.class);
   // class variables (members)
   private ThreadLocal<DateFormat> df;    //TLTL   
   // private DateFormat df;                 //NTLNTL
@@ -72,7 +77,7 @@ public class DateFormatCallable implements Callable<Result> {
    */
   @Override
   public Result call() {
-    System.out.println(Thread.currentThread() + " started executing...");
+    LOGGER.info(Thread.currentThread() + " started executing...");
     Result result = new Result();
 
     // Convert date value to date 5 times
@@ -90,7 +95,7 @@ public class DateFormatCallable implements Callable<Result> {
 
     }
 
-    System.out.println(Thread.currentThread() + " finished processing part of the thread");
+    LOGGER.info(Thread.currentThread() + " finished processing part of the thread");
 
     return result;
   }

typeobjectpattern/src/main/java/com/iluwatar/typeobject/App.java

@@ -25,6 +25,8 @@ package com.iluwatar.typeobject;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import org.json.simple.parser.ParseException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**<p>Type object pattern is the pattern we use when the OOP concept of creating a base class and
  * inheriting from it just doesn't work for the case in hand. This happens when we either don't know 
@@ -45,6 +47,7 @@ import org.json.simple.parser.ParseException;
 
 public class App {
 
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
   /**
    * Program entry point.
    * @param args command line args
@@ -62,9 +65,9 @@ public class App {
       CellPool pool = new CellPool(numOfRows * numOfRows + 5);
       CandyGame cg = new CandyGame(numOfRows, pool);
       if (round > 1) {
-        System.out.println("Refreshing..");
+        LOGGER.info("Refreshing..");
       } else {
-        System.out.println("Starting game..");
+        LOGGER.info("Starting game..");
       }
       cg.printGameStatus();
       end = System.currentTimeMillis();
@@ -72,13 +75,13 @@ public class App {
       pointsWon += cg.totalPoints;
       end = System.currentTimeMillis();
     }
-    System.out.println("Game Over");
+    LOGGER.info("Game Over");
     if (pointsWon >= toWin) {
-      System.out.println(pointsWon);
+      LOGGER.info("" + pointsWon);
-      System.out.println("You win!!");
+      LOGGER.info("You win!!");
     } else {
-      System.out.println(pointsWon);
+      LOGGER.info("" + pointsWon);
-      System.out.println("Sorry, you lose!");
+      LOGGER.info("Sorry, you lose!");
     }
   }
 }

typeobjectpattern/src/main/java/com/iluwatar/typeobject/CandyGame.java

@@ -24,6 +24,8 @@ package com.iluwatar.typeobject;
 
 import java.util.ArrayList;
 import com.iluwatar.typeobject.Candy.Type;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * The CandyGame class contains the rules for the continuation of the game and has
@@ -31,6 +33,9 @@ import com.iluwatar.typeobject.Candy.Type;
  */
 
 public class CandyGame {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(CandyGame.class);
+  
   Cell[][] cells;
   CellPool pool;
   int totalPoints;
@@ -57,21 +62,21 @@ public class CandyGame {
   }
   
   void printGameStatus() {
-    System.out.println("");
+    LOGGER.info("");
     for (int i = 0; i < cells.length; i++) {
       for (int j = 0; j < cells.length; j++) {
         String candyName = cells[i][j].candy.name;
         if (candyName.length() < 20) {
           int totalSpaces = 20 - candyName.length();
-          System.out.print(numOfSpaces(totalSpaces / 2) + cells[i][j].candy.name
+          LOGGER.info(numOfSpaces(totalSpaces / 2) + cells[i][j].candy.name
               + numOfSpaces(totalSpaces - totalSpaces / 2) + "|");
         } else {
-          System.out.print(candyName + "|");
+          LOGGER.info(candyName + "|");
         }
       }
-      System.out.println("");
+      LOGGER.info("");
     }
-    System.out.println("");
+    LOGGER.info("");
   }
   
   ArrayList<Cell> adjacentCells(int yIndex, int xIndex) {
@@ -121,7 +126,7 @@ public class CandyGame {
   }
   
   void handleChange(int points) {
-    System.out.println("+" + points + " points!");
+    LOGGER.info("+" + points + " points!");
     this.totalPoints += points; 
     printGameStatus();
   }