From 32bdc0690f44f475e3348c28092a47f8ac8b9e37 Mon Sep 17 00:00:00 2001
From: bsmahi <bs.mahi@gmail.com>
Date: Thu, 18 Aug 2022 07:05:28 +0530
Subject: [PATCH] Upgrade to Spring Boot 3.0.0-M4

---
 .gitignore                                    |   1 +
 Step01.md                                     |  15 ++-
 Step02.md                                     |  15 ++-
 Step03.md                                     |  15 ++-
 Step04.md                                     |  15 ++-
 Step05.md                                     |  15 ++-
 Step06.md                                     |  15 ++-
 Step07.md                                     |  18 +--
 Step08.md                                     |  21 ++--
 Step09.md                                     |  21 ++--
 Step10.md                                     |  21 ++--
 Step11.md                                     |  24 ++--
 Step13.md                                     |  24 ++--
 Step14.md                                     |  48 ++++----
 Step15.md                                     |  52 ++++-----
 Step17.md                                     |  64 +++++------
 Step20.md                                     |  70 ++++++------
 Step24.md                                     |  73 +++++++------
 Step25.md                                     |  76 ++++++-------
 Step27.md                                     |  70 ++++++------
 pom.xml                                       |  19 ++--
 .../filter/LoginRequiredFilter.java           |  43 ++++----
 .../com/in28minutes/login/LoginService.java   |   9 +-
 .../com/in28minutes/login/LoginServlet.java   |  46 ++++----
 .../com/in28minutes/logout/LogoutServlet.java |  11 +-
 .../com/in28minutes/todo/AddTodoServlet.java  |  30 ++---
 .../in28minutes/todo/DeleteTodoServlet.java   |  13 +--
 .../com/in28minutes/todo/ListTodoServlet.java |  13 +--
 src/main/java/com/in28minutes/todo/Todo.java  | 103 +++++++++---------
 .../com/in28minutes/todo/TodoService.java     |  31 +++---
 30 files changed, 526 insertions(+), 465 deletions(-)

diff --git a/.gitignore b/.gitignore
index 0c4ca8e..b13cfc7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,6 +25,7 @@
 mvnw
 target
 *.DS_Store
+.idea
 
 # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
 hs_err_pid*
diff --git a/Step01.md b/Step01.md
index de90a25..93a74a0 100644
--- a/Step01.md
+++ b/Step01.md
@@ -12,7 +12,7 @@
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -23,17 +23,22 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
diff --git a/Step02.md b/Step02.md
index 03af3eb..063d7de 100644
--- a/Step02.md
+++ b/Step02.md
@@ -17,7 +17,7 @@
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -28,17 +28,22 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
diff --git a/Step03.md b/Step03.md
index e7d42bf..0d6405b 100644
--- a/Step03.md
+++ b/Step03.md
@@ -16,7 +16,7 @@
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -27,17 +27,22 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1/version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
diff --git a/Step04.md b/Step04.md
index 0dd7842..9f8b1db 100644
--- a/Step04.md
+++ b/Step04.md
@@ -12,7 +12,7 @@
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -23,17 +23,22 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
diff --git a/Step05.md b/Step05.md
index 386f5bc..440466d 100644
--- a/Step05.md
+++ b/Step05.md
@@ -12,7 +12,7 @@
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -23,17 +23,22 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
diff --git a/Step06.md b/Step06.md
index 37e4949..4b03234 100644
--- a/Step06.md
+++ b/Step06.md
@@ -12,7 +12,7 @@
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -23,17 +23,22 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
diff --git a/Step07.md b/Step07.md
index c7378d6..86616cb 100644
--- a/Step07.md
+++ b/Step07.md
@@ -12,7 +12,7 @@
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -23,17 +23,22 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -68,11 +73,10 @@ import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-
 @WebServlet(urlPatterns = "/login.do")
 public class LoginServlet extends HttpServlet {
 
-	private LoginService service = new LoginService();
+	private final LoginService userValidationService = new LoginService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
diff --git a/Step08.md b/Step08.md
index 76c9a8e..d324eeb 100644
--- a/Step08.md
+++ b/Step08.md
@@ -12,7 +12,7 @@
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -23,17 +23,22 @@
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -74,8 +79,8 @@ import webapp.todo.TodoService;
 @WebServlet(urlPatterns = "/login.do")
 public class LoginServlet extends HttpServlet {
 
-	private LoginService service = new LoginService();
-	private TodoService todoService = new TodoService();
+    private final LoginService userValidationService = new LoginService();
+    private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -138,7 +143,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList();
+	private static final List<Todo> todos = new ArrayList();
 
 	static {
 		todos.add(new Todo("Learn Web Application"));
diff --git a/Step09.md b/Step09.md
index 859266f..b8f7974 100644
--- a/Step09.md
+++ b/Step09.md
@@ -12,7 +12,7 @@ pom.xml
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -23,17 +23,22 @@ pom.xml
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -75,8 +80,8 @@ import in28minutes.todo.TodoService;
 public class LoginServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private LoginService service = new LoginService();
-	private TodoService todoService = new TodoService();
+    private final LoginService userValidationService = new LoginService();
+    private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -139,7 +144,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
 
 	static {
 		todos.add(new Todo("Learn Web Application"));
diff --git a/Step10.md b/Step10.md
index f573a22..0557ba0 100644
--- a/Step10.md
+++ b/Step10.md
@@ -12,7 +12,7 @@ pom.xml
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 	</dependencies>
@@ -23,17 +23,22 @@ pom.xml
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -73,7 +78,7 @@ import javax.servlet.http.HttpServletResponse;
 public class LoginServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private LoginService service = new LoginService();
+	private final LoginService service = new LoginService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -134,7 +139,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
 
 	static {
 		todos.add(new Todo("Learn Web Application"));
@@ -163,7 +168,7 @@ import javax.servlet.http.HttpServletResponse;
 public class TodoServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
diff --git a/Step11.md b/Step11.md
index cbb38fd..c0dd237 100644
--- a/Step11.md
+++ b/Step11.md
@@ -12,15 +12,14 @@ pom.xml
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
         <dependency>
             <groupId>javax.servlet</groupId>
             <artifactId>jstl</artifactId>
             <version>1.2</version>
-        </dependency>
-		
+        </dependency>		
 	</dependencies>
 
 	<build>
@@ -29,17 +28,22 @@ pom.xml
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -79,7 +83,7 @@ import javax.servlet.http.HttpServletResponse;
 public class LoginServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private LoginService service = new LoginService();
+	private final LoginService service = new LoginService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -140,7 +144,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
 
 	static {
 		todos.add(new Todo("Learn Web Application"));
@@ -169,7 +173,7 @@ import javax.servlet.http.HttpServletResponse;
 public class TodoServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
diff --git a/Step13.md b/Step13.md
index 8c15a34..bcb7c00 100644
--- a/Step13.md
+++ b/Step13.md
@@ -12,15 +12,14 @@ pom.xml
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
         <dependency>
             <groupId>javax.servlet</groupId>
             <artifactId>jstl</artifactId>
             <version>1.2</version>
-        </dependency>
-		
+        </dependency>		
 	</dependencies>
 
 	<build>
@@ -29,17 +28,22 @@ pom.xml
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -79,7 +83,7 @@ import javax.servlet.http.HttpServletResponse;
 public class LoginServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private LoginService service = new LoginService();
+	private final LoginService service = new LoginService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -140,7 +144,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
 
 	static {
 		todos.add(new Todo("Learn Web Application"));
@@ -173,7 +177,7 @@ import javax.servlet.http.HttpServletResponse;
 public class TodoServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
diff --git a/Step14.md b/Step14.md
index f1c4732..ee5b1e5 100644
--- a/Step14.md
+++ b/Step14.md
@@ -12,7 +12,7 @@ pom.xml
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
         <dependency>
@@ -29,17 +29,22 @@ pom.xml
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -79,7 +84,7 @@ import javax.servlet.http.HttpServletResponse;
 public class LoginServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private LoginService service = new LoginService();
+	private final LoginService service = new LoginService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -122,7 +127,7 @@ import javax.servlet.http.HttpServletResponse;
 public class DeleteTodoServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -148,7 +153,7 @@ import javax.servlet.http.HttpServletResponse;
 public class ListTodoServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -207,20 +212,17 @@ public class Todo {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
-		if (this == obj)
-			return true;
-		if (obj == null)
-			return false;
-		if (getClass() != obj.getClass())
-			return false;
-		Todo other = (Todo) obj;
-		if (name == null) {
-			if (other.name != null)
-				return false;
-		} else if (!name.equals(other.name))
-			return false;
-		return true;
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Todo other = (Todo) obj;
+        if (name == null) {
+			return other.name == null;
+        } else return name.equals(other.name);
 	}
 
 }
@@ -233,7 +235,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
 
 	static {
 		todos.add(new Todo("Learn Web Application"));
diff --git a/Step15.md b/Step15.md
index 5b4c64b..480061c 100644
--- a/Step15.md
+++ b/Step15.md
@@ -12,7 +12,7 @@ pom.xml
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 		<dependency>
@@ -25,12 +25,12 @@ pom.xml
 		<dependency>
 			<groupId>org.webjars</groupId>
 			<artifactId>bootstrap</artifactId>
-			<version>3.3.6</version>
+			<version>5.1.3</version>
 		</dependency>
 		<dependency>
 			<groupId>org.webjars</groupId>
 			<artifactId>jquery</artifactId>
-			<version>1.9.1</version>
+			<version>3.6.0</version>
 		</dependency>
 
 	</dependencies>
@@ -41,17 +41,22 @@ pom.xml
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -91,7 +96,7 @@ import javax.servlet.http.HttpServletResponse;
 public class LoginServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private LoginService service = new LoginService();
+	private final LoginService service = new LoginService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -134,7 +139,7 @@ import javax.servlet.http.HttpServletResponse;
 public class DeleteTodoServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -160,7 +165,7 @@ import javax.servlet.http.HttpServletResponse;
 public class ListTodoServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -219,20 +224,17 @@ public class Todo {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
-		if (this == obj)
-			return true;
-		if (obj == null)
-			return false;
-		if (getClass() != obj.getClass())
-			return false;
-		Todo other = (Todo) obj;
-		if (name == null) {
-			if (other.name != null)
-				return false;
-		} else if (!name.equals(other.name))
-			return false;
-		return true;
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Todo other = (Todo) obj;
+        if (name == null) {
+			return other.name == null;
+        } else return name.equals(other.name);
 	}
 
 }
@@ -245,7 +247,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
 
 	static {
 		todos.add(new Todo("Learn Web Application"));
diff --git a/Step17.md b/Step17.md
index e0a9ffd..a8a28b6 100644
--- a/Step17.md
+++ b/Step17.md
@@ -5,8 +5,7 @@ Bootstrap Sample Page
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
-	rel="stylesheet">
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css" rel="stylesheet">
 
 <style>
 	.footer {
@@ -46,8 +45,8 @@ Bootstrap Sample Page
 		<p>footer content</p>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
@@ -68,7 +67,7 @@ pom.xml
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-web-api</artifactId>
-			<version>6.0</version>
+			<version>8.0.1</version>
 			<scope>provided</scope>
 		</dependency>
 		<dependency>
@@ -81,12 +80,12 @@ pom.xml
 		<dependency>
 			<groupId>org.webjars</groupId>
 			<artifactId>bootstrap</artifactId>
-			<version>3.3.6</version>
+			<version>5.1.3</version>
 		</dependency>
 		<dependency>
 			<groupId>org.webjars</groupId>
 			<artifactId>jquery</artifactId>
-			<version>1.9.1</version>
+			<version>3.6.0</version>
 		</dependency>
 
 	</dependencies>
@@ -97,17 +96,22 @@ pom.xml
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.2</version>
+					<version>3.8.1</version>
 					<configuration>
 						<verbose>true</verbose>
-						<source>1.7</source>
-						<target>1.7</target>
+						<source>17</source>
+						<target>17</target>
 						<showWarnings>true</showWarnings>
 					</configuration>
 				</plugin>
 				<plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
+				<plugin>
 					<groupId>org.apache.tomcat.maven</groupId>
-					<artifactId>tomcat7-maven-plugin</artifactId>
+					<artifactId>tomcat8-maven-plugin</artifactId>
 					<version>2.2</version>
 					<configuration>
 						<path>/</path>
@@ -142,12 +146,11 @@ import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-
 @WebServlet(urlPatterns = "/login.do")
 public class LoginServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private LoginService service = new LoginService();
+	private final LoginService service = new LoginService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -190,7 +193,7 @@ import javax.servlet.http.HttpServletResponse;
 public class DeleteTodoServlet extends HttpServlet {
 
 	private static final long serialVersionUID = 1L;
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	@Override
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
@@ -275,20 +278,17 @@ public class Todo {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
-		if (this == obj)
-			return true;
-		if (obj == null)
-			return false;
-		if (getClass() != obj.getClass())
-			return false;
-		Todo other = (Todo) obj;
-		if (name == null) {
-			if (other.name != null)
-				return false;
-		} else if (!name.equals(other.name))
-			return false;
-		return true;
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Todo other = (Todo) obj;
+        if (name == null) {
+			return other.name == null;
+        } else return name.equals(other.name);
 	}
 
 }
@@ -301,7 +301,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
 
 	static {
 		todos.add(new Todo("Learn Web Application"));
@@ -346,7 +346,7 @@ src\main\webapp\WEB-INF\views\todo.jsp
 <head>
 <title>Yahoo!!</title>
 <!-- Bootstrap core CSS -->
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css"
 	rel="stylesheet">
 
 <style>
@@ -413,8 +413,8 @@ padding: 0 15px;
 		</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
diff --git a/Step20.md b/Step20.md
index 49fd1b9..70186e1 100644
--- a/Step20.md
+++ b/Step20.md
@@ -13,7 +13,7 @@
         <dependency>
             <groupId>javax</groupId>
             <artifactId>javaee-web-api</artifactId>
-            <version>6.0</version>
+            <version>8.0.1</version>
             <scope>provided</scope>
         </dependency>
         <dependency>
@@ -25,12 +25,12 @@
  		<dependency>
             <groupId>org.webjars</groupId>
             <artifactId>bootstrap</artifactId>
-            <version>3.3.6</version>
+            <version>5.1.3</version>
         </dependency>
         <dependency>
             <groupId>org.webjars</groupId>
             <artifactId>jquery</artifactId>
-            <version>1.9.1</version>
+            <version>3.6.0</version>
         </dependency>
     </dependencies>
 
@@ -40,17 +40,22 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-compiler-plugin</artifactId>
-                    <version>3.2</version>
+                    <version>3.8.1</version>
                     <configuration>
                         <verbose>true</verbose>
-                        <source>1.7</source>
-                        <target>1.7</target>
+                        <source>17</source>
+                        <target>17</target>
                         <showWarnings>true</showWarnings>
                     </configuration>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
                 <plugin>
                     <groupId>org.apache.tomcat.maven</groupId>
-                    <artifactId>tomcat7-maven-plugin</artifactId>
+                    <artifactId>tomcat8-maven-plugin</artifactId>
                     <version>2.2</version>
                     <configuration>
                         <path>/</path>
@@ -137,8 +142,8 @@ import com.in28minutes.todo.TodoService;
 @WebServlet(urlPatterns = "/login.do")
 public class LoginServlet extends HttpServlet {
 
-	private LoginService userValidationService = new LoginService();
-	private TodoService todoService = new TodoService();
+	private final LoginService userValidationService = new LoginService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -202,7 +207,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/add-todo.do")
 public class AddTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doPost(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -227,7 +232,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/delete-todo.do")
 public class DeleteTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -251,7 +256,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/todo.do")
 public class ListTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -295,20 +300,17 @@ public class Todo {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
-		if (this == obj)
-			return true;
-		if (obj == null)
-			return false;
-		if (getClass() != obj.getClass())
-			return false;
-		Todo other = (Todo) obj;
-		if (name == null) {
-			if (other.name != null)
-				return false;
-		} else if (!name.equals(other.name))
-			return false;
-		return true;
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Todo other = (Todo) obj;
+        if (name == null) {
+			return other.name == null;
+        } else return name.equals(other.name);
 	}
 
 }
@@ -321,7 +323,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
+	
 	static {
 		todos.add(new Todo("Learn Web Application Development"));
 		todos.add(new Todo("Learn Spring MVC"));
@@ -349,8 +352,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
-	rel="stylesheet">
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css" rel="stylesheet">
 
 <style>
 .footer {
@@ -397,8 +399,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
@@ -411,7 +413,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css"
 	rel="stylesheet">
 
 <style>
@@ -467,8 +469,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
diff --git a/Step24.md b/Step24.md
index b69ea69..c45cefa 100644
--- a/Step24.md
+++ b/Step24.md
@@ -13,7 +13,7 @@
         <dependency>
             <groupId>javax</groupId>
             <artifactId>javaee-web-api</artifactId>
-            <version>6.0</version>
+            <version>8.0.1</version>
             <scope>provided</scope>
         </dependency>
         <dependency>
@@ -25,12 +25,12 @@
  		<dependency>
             <groupId>org.webjars</groupId>
             <artifactId>bootstrap</artifactId>
-            <version>3.3.6</version>
+            <version>5.1.3</version>
         </dependency>
         <dependency>
             <groupId>org.webjars</groupId>
             <artifactId>jquery</artifactId>
-            <version>1.9.1</version>
+            <version>3.6.0</version>
         </dependency>
     </dependencies>
 
@@ -40,17 +40,22 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-compiler-plugin</artifactId>
-                    <version>3.2</version>
+                    <version>3.8.1</version>
                     <configuration>
                         <verbose>true</verbose>
-                        <source>1.7</source>
-                        <target>1.7</target>
+                        <source>17</source>
+                        <target>17</target>
                         <showWarnings>true</showWarnings>
                     </configuration>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
                 <plugin>
                     <groupId>org.apache.tomcat.maven</groupId>
-                    <artifactId>tomcat7-maven-plugin</artifactId>
+                    <artifactId>tomcat8-maven-plugin</artifactId>
                     <version>2.2</version>
                     <configuration>
                         <path>/</path>
@@ -137,8 +142,8 @@ import com.in28minutes.todo.TodoService;
 @WebServlet(urlPatterns = "/login.do")
 public class LoginServlet extends HttpServlet {
 
-	private LoginService userValidationService = new LoginService();
-	private TodoService todoService = new TodoService();
+	private final LoginService userValidationService = new LoginService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -202,7 +207,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/add-todo.do")
 public class AddTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -233,7 +238,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/delete-todo.do")
 public class DeleteTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -257,7 +262,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/list-todos.do")
 public class ListTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -301,20 +306,17 @@ public class Todo {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
-		if (this == obj)
-			return true;
-		if (obj == null)
-			return false;
-		if (getClass() != obj.getClass())
-			return false;
-		Todo other = (Todo) obj;
-		if (name == null) {
-			if (other.name != null)
-				return false;
-		} else if (!name.equals(other.name))
-			return false;
-		return true;
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Todo other = (Todo) obj;
+        if (name == null) {
+			return other.name == null;
+        } else return name.equals(other.name);
 	}
 
 }
@@ -355,8 +357,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
-	rel="stylesheet">
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css" rel="stylesheet">
 
 <style>
 .footer {
@@ -399,8 +400,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
@@ -413,7 +414,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css"
 	rel="stylesheet">
 
 <style>
@@ -467,8 +468,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
@@ -481,7 +482,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css"
 	rel="stylesheet">
 
 <style>
@@ -529,8 +530,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
diff --git a/Step25.md b/Step25.md
index 0987b59..85f5471 100644
--- a/Step25.md
+++ b/Step25.md
@@ -13,7 +13,7 @@
         <dependency>
             <groupId>javax</groupId>
             <artifactId>javaee-web-api</artifactId>
-            <version>6.0</version>
+            <version>8.0.1</version>
             <scope>provided</scope>
         </dependency>
         <dependency>
@@ -25,12 +25,12 @@
  		<dependency>
             <groupId>org.webjars</groupId>
             <artifactId>bootstrap</artifactId>
-            <version>3.3.6</version>
+            <version>5.1.3</version>
         </dependency>
         <dependency>
             <groupId>org.webjars</groupId>
             <artifactId>jquery</artifactId>
-            <version>1.9.1</version>
+            <version>3.6.0</version>
         </dependency>
     </dependencies>
 
@@ -40,17 +40,22 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-compiler-plugin</artifactId>
-                    <version>3.2</version>
+                    <version>3.8.1</version>
                     <configuration>
                         <verbose>true</verbose>
-                        <source>1.7</source>
-                        <target>1.7</target>
+                        <source>17</source>
+                        <target>17</target>
                         <showWarnings>true</showWarnings>
                     </configuration>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
                 <plugin>
                     <groupId>org.apache.tomcat.maven</groupId>
-                    <artifactId>tomcat7-maven-plugin</artifactId>
+                    <artifactId>tomcat8-maven-plugin</artifactId>
                     <version>2.2</version>
                     <configuration>
                         <path>/</path>
@@ -137,8 +142,8 @@ import com.in28minutes.todo.TodoService;
 @WebServlet(urlPatterns = "/login.do")
 public class LoginServlet extends HttpServlet {
 
-	private LoginService userValidationService = new LoginService();
-	private TodoService todoService = new TodoService();
+	private final LoginService userValidationService = new LoginService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -202,7 +207,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/add-todo.do")
 public class AddTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -234,7 +239,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/delete-todo.do")
 public class DeleteTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -259,7 +264,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/list-todos.do")
 public class ListTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -313,20 +318,17 @@ public class Todo {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
-		if (this == obj)
-			return true;
-		if (obj == null)
-			return false;
-		if (getClass() != obj.getClass())
-			return false;
-		Todo other = (Todo) obj;
-		if (name == null) {
-			if (other.name != null)
-				return false;
-		} else if (!name.equals(other.name))
-			return false;
-		return true;
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Todo other = (Todo) obj;
+        if (name == null) {
+			return other.name == null;
+        } else return name.equals(other.name);
 	}
 
 }
@@ -339,7 +341,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
+	
 	static {
 		todos.add(new Todo("Learn Web Application Development", "Study"));
 		todos.add(new Todo("Learn Spring MVC", "Study"));
@@ -367,7 +370,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css"
 	rel="stylesheet">
 
 <style>
@@ -413,8 +416,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
@@ -427,7 +430,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css"
 	rel="stylesheet">
 
 <style>
@@ -481,8 +484,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
@@ -495,8 +498,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
-	rel="stylesheet">
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css" rel="stylesheet">
 
 <style>
 .footer {
@@ -543,8 +545,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
diff --git a/Step27.md b/Step27.md
index e9ab516..8fcf200 100644
--- a/Step27.md
+++ b/Step27.md
@@ -13,7 +13,7 @@
         <dependency>
             <groupId>javax</groupId>
             <artifactId>javaee-web-api</artifactId>
-            <version>6.0</version>
+            <version>8.0.1</version>
             <scope>provided</scope>
         </dependency>
         <dependency>
@@ -25,12 +25,12 @@
  		<dependency>
             <groupId>org.webjars</groupId>
             <artifactId>bootstrap</artifactId>
-            <version>3.3.6</version>
+            <version>5.1.3</version>
         </dependency>
         <dependency>
             <groupId>org.webjars</groupId>
             <artifactId>jquery</artifactId>
-            <version>1.9.1</version>
+            <version>3.6.0</version>
         </dependency>
     </dependencies>
 
@@ -40,17 +40,22 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-compiler-plugin</artifactId>
-                    <version>3.2</version>
+                    <version>3.8.1</version>
                     <configuration>
                         <verbose>true</verbose>
-                        <source>1.7</source>
-                        <target>1.7</target>
+                        <source>17</source>
+                        <target>17</target>
                         <showWarnings>true</showWarnings>
                     </configuration>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
                 <plugin>
                     <groupId>org.apache.tomcat.maven</groupId>
-                    <artifactId>tomcat7-maven-plugin</artifactId>
+                    <artifactId>tomcat8-maven-plugin</artifactId>
                     <version>2.2</version>
                     <configuration>
                         <path>/</path>
@@ -137,8 +142,8 @@ import com.in28minutes.todo.TodoService;
 @WebServlet(urlPatterns = "/login.do")
 public class LoginServlet extends HttpServlet {
 
-	private LoginService userValidationService = new LoginService();
-	private TodoService todoService = new TodoService();
+	private final LoginService userValidationService = new LoginService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -202,7 +207,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/add-todo.do")
 public class AddTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -234,7 +239,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/delete-todo.do")
 public class DeleteTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -259,7 +264,7 @@ import javax.servlet.http.HttpServletResponse;
 @WebServlet(urlPatterns = "/list-todos.do")
 public class ListTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+	private final TodoService todoService = new TodoService();
 
 	protected void doGet(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException, IOException {
@@ -313,20 +318,17 @@ public class Todo {
 	}
 
 	@Override
-	public boolean equals(Object obj) {
-		if (this == obj)
-			return true;
-		if (obj == null)
-			return false;
-		if (getClass() != obj.getClass())
-			return false;
-		Todo other = (Todo) obj;
-		if (name == null) {
-			if (other.name != null)
-				return false;
-		} else if (!name.equals(other.name))
-			return false;
-		return true;
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Todo other = (Todo) obj;
+        if (name == null) {
+			return other.name == null;
+        } else return name.equals(other.name);
 	}
 
 }
@@ -339,7 +341,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
+	private static final List<Todo> todos = new ArrayList<Todo>();
+	
 	static {
 		todos.add(new Todo("Learn Web Application Development", "Study"));
 		todos.add(new Todo("Learn Spring MVC", "Study"));
@@ -367,8 +370,8 @@ public class TodoService {
 	<div>footer content</div>
 </footer>
 
-<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
@@ -381,8 +384,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
-	rel="stylesheet">
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css" rel="stylesheet">
 
 <style>
 .footer {
@@ -481,7 +483,7 @@ public class TodoService {
 <html>
 <head>
 <title>Todos</title>
-<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
+<link href="webjars/bootstrap/5.1.3/css/bootstrap.min.css"
 	rel="stylesheet">
 
 <style>
@@ -529,8 +531,8 @@ public class TodoService {
 		<div>footer content</div>
 	</footer>
 
-	<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
-	<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
+	<script src="webjars/jquery/3.6.0/jquery.min.js"></script>
+	<script src="webjars/bootstrap/5.1.3/js/bootstrap.min.js"></script>
 
 </body>
 
diff --git a/pom.xml b/pom.xml
index 197b2dd..4655cf8 100644
--- a/pom.xml
+++ b/pom.xml
@@ -10,7 +10,7 @@
         <dependency>
             <groupId>javax</groupId>
             <artifactId>javaee-web-api</artifactId>
-            <version>6.0</version>
+            <version>8.0.1</version>
             <scope>provided</scope>
         </dependency>
         <dependency>
@@ -22,12 +22,12 @@
  		<dependency>
             <groupId>org.webjars</groupId>
             <artifactId>bootstrap</artifactId>
-            <version>3.3.6</version>
+            <version>5.1.3</version>
         </dependency>
         <dependency>
             <groupId>org.webjars</groupId>
             <artifactId>jquery</artifactId>
-            <version>1.9.1</version>
+            <version>3.6.0</version>
         </dependency>
     </dependencies>
 
@@ -37,17 +37,22 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-compiler-plugin</artifactId>
-                    <version>3.2</version>
+                    <version>3.8.1</version>
                     <configuration>
                         <verbose>true</verbose>
-                        <source>1.7</source>
-                        <target>1.7</target>
+                        <source>17</source>
+                        <target>17</target>
                         <showWarnings>true</showWarnings>
                     </configuration>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-war-plugin</artifactId>
+                    <version>3.3.1</version>
+                </plugin>
                 <plugin>
                     <groupId>org.apache.tomcat.maven</groupId>
-                    <artifactId>tomcat7-maven-plugin</artifactId>
+                    <artifactId>tomcat8-maven-plugin</artifactId>
                     <version>2.2</version>
                     <configuration>
                         <path>/</path>
diff --git a/src/main/java/com/in28minutes/filter/LoginRequiredFilter.java b/src/main/java/com/in28minutes/filter/LoginRequiredFilter.java
index 2226edf..4d09a72 100644
--- a/src/main/java/com/in28minutes/filter/LoginRequiredFilter.java
+++ b/src/main/java/com/in28minutes/filter/LoginRequiredFilter.java
@@ -14,27 +14,26 @@
 @WebFilter(urlPatterns = "*.do")
 public class LoginRequiredFilter implements Filter {
 
-	@Override
-	public void destroy() {
-
-	}
-
-	@Override
-	public void doFilter(ServletRequest servletRequest,
-			ServletResponse servletResponse, FilterChain chain)
-			throws IOException, ServletException {
-		HttpServletRequest request = (HttpServletRequest) servletRequest;
-
-		if (request.getSession().getAttribute("name") != null) {
-			chain.doFilter(servletRequest, servletResponse);
-		} else {
-			request.getRequestDispatcher("/login.do").forward(servletRequest,
-					servletResponse);
-		}
-	}
-
-	@Override
-	public void init(FilterConfig arg0) throws ServletException {
-	}
+    @Override
+    public void destroy() {
+
+    }
+
+    @Override
+    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain chain)
+            throws IOException, ServletException {
+        HttpServletRequest request = (HttpServletRequest) servletRequest;
+
+        if (request.getSession().getAttribute("name") != null) {
+            chain.doFilter(servletRequest, servletResponse);
+        } else {
+            request.getRequestDispatcher("/login.do").forward(servletRequest,
+                    servletResponse);
+        }
+    }
+
+    @Override
+    public void init(FilterConfig arg0) throws ServletException {
+    }
 
 }
diff --git a/src/main/java/com/in28minutes/login/LoginService.java b/src/main/java/com/in28minutes/login/LoginService.java
index cc84594..7d74b85 100644
--- a/src/main/java/com/in28minutes/login/LoginService.java
+++ b/src/main/java/com/in28minutes/login/LoginService.java
@@ -2,11 +2,8 @@
 
 public class LoginService {
 
-	public boolean isUserValid(String user, String password) {
-		if (user.equals("in28Minutes") && password.equals("dummy"))
-			return true;
-
-		return false;
-	}
+    public boolean isUserValid(String user, String password) {
+        return user.equals("in28Minutes") && password.equals("dummy");
+    }
 
 }
diff --git a/src/main/java/com/in28minutes/login/LoginServlet.java b/src/main/java/com/in28minutes/login/LoginServlet.java
index 1bde672..d6ebc52 100644
--- a/src/main/java/com/in28minutes/login/LoginServlet.java
+++ b/src/main/java/com/in28minutes/login/LoginServlet.java
@@ -25,30 +25,26 @@
 @WebServlet(urlPatterns = "/login.do")
 public class LoginServlet extends HttpServlet {
 
-	private LoginService userValidationService = new LoginService();
-	private TodoService todoService = new TodoService();
-
-	protected void doGet(HttpServletRequest request,
-			HttpServletResponse response) throws ServletException, IOException {
-		request.getRequestDispatcher("/WEB-INF/views/login.jsp").forward(
-				request, response);
-	}
-
-	protected void doPost(HttpServletRequest request,
-			HttpServletResponse response) throws ServletException, IOException {
-		String name = request.getParameter("name");
-		String password = request.getParameter("password");
-
-		boolean isUserValid = userValidationService.isUserValid(name, password);
-
-		if (isUserValid) {
-			request.getSession().setAttribute("name", name);
-			response.sendRedirect("/list-todos.do");
-		} else {
-			request.setAttribute("errorMessage", "Invalid Credentials!");
-			request.getRequestDispatcher("/WEB-INF/views/login.jsp").forward(
-					request, response);
-		}
-	}
+    private final LoginService userValidationService = new LoginService();
+
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        request.getRequestDispatcher("/WEB-INF/views/login.jsp").forward(request, response);
+    }
+
+    protected void doPost(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+        String name = request.getParameter("name");
+        String password = request.getParameter("password");
+
+        boolean isUserValid = userValidationService.isUserValid(name, password);
+
+        if (isUserValid) {
+            request.getSession().setAttribute("name", name);
+            response.sendRedirect("/list-todos.do");
+        } else {
+            request.setAttribute("errorMessage", "Invalid Credentials!");
+            request.getRequestDispatcher("/WEB-INF/views/login.jsp").forward(request, response);
+        }
+    }
 
 }
\ No newline at end of file
diff --git a/src/main/java/com/in28minutes/logout/LogoutServlet.java b/src/main/java/com/in28minutes/logout/LogoutServlet.java
index 61ad7ad..ff594d2 100644
--- a/src/main/java/com/in28minutes/logout/LogoutServlet.java
+++ b/src/main/java/com/in28minutes/logout/LogoutServlet.java
@@ -10,10 +10,9 @@
 
 @WebServlet(urlPatterns = "/logout.do")
 public class LogoutServlet extends HttpServlet {
-	protected void doGet(HttpServletRequest request,
-			HttpServletResponse response) throws ServletException, IOException {
-		request.getSession().invalidate();
-		request.getRequestDispatcher("/WEB-INF/views/login.jsp").forward(
-				request, response);
-	}
+    protected void doGet(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+        request.getSession().invalidate();
+        request.getRequestDispatcher("/WEB-INF/views/login.jsp").forward(request, response);
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/com/in28minutes/todo/AddTodoServlet.java b/src/main/java/com/in28minutes/todo/AddTodoServlet.java
index 758c8ba..f1dd6f3 100644
--- a/src/main/java/com/in28minutes/todo/AddTodoServlet.java
+++ b/src/main/java/com/in28minutes/todo/AddTodoServlet.java
@@ -20,19 +20,19 @@
 @WebServlet(urlPatterns = "/add-todo.do")
 public class AddTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
-
-	protected void doGet(HttpServletRequest request,
-			HttpServletResponse response) throws ServletException, IOException {
-		request.getRequestDispatcher("/WEB-INF/views/add-todo.jsp").forward(
-				request, response);
-	}
-
-	protected void doPost(HttpServletRequest request,
-			HttpServletResponse response) throws ServletException, IOException {
-		String newTodo = request.getParameter("todo");
-		String category = request.getParameter("category");
-		todoService.addTodo(new Todo(newTodo, category));
-		response.sendRedirect("/list-todos.do");
-	}
+    private final TodoService todoService = new TodoService();
+
+    protected void doGet(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+        request.getRequestDispatcher("/WEB-INF/views/add-todo.jsp").forward(
+                request, response);
+    }
+
+    protected void doPost(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+        String newTodo = request.getParameter("todo");
+        String category = request.getParameter("category");
+        todoService.addTodo(new Todo(newTodo, category));
+        response.sendRedirect("/list-todos.do");
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/com/in28minutes/todo/DeleteTodoServlet.java b/src/main/java/com/in28minutes/todo/DeleteTodoServlet.java
index 5577ef4..2fed569 100644
--- a/src/main/java/com/in28minutes/todo/DeleteTodoServlet.java
+++ b/src/main/java/com/in28minutes/todo/DeleteTodoServlet.java
@@ -11,12 +11,11 @@
 @WebServlet(urlPatterns = "/delete-todo.do")
 public class DeleteTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+    private final TodoService todoService = new TodoService();
 
-	protected void doGet(HttpServletRequest request,
-			HttpServletResponse response) throws ServletException, IOException {
-		todoService.deleteTodo(new Todo(request.getParameter("todo"), request
-				.getParameter("category")));
-		response.sendRedirect("/list-todos.do");
-	}
+    protected void doGet(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+        todoService.deleteTodo(new Todo(request.getParameter("todo"), request.getParameter("category")));
+        response.sendRedirect("/list-todos.do");
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/com/in28minutes/todo/ListTodoServlet.java b/src/main/java/com/in28minutes/todo/ListTodoServlet.java
index 94ed5e8..aa2b361 100644
--- a/src/main/java/com/in28minutes/todo/ListTodoServlet.java
+++ b/src/main/java/com/in28minutes/todo/ListTodoServlet.java
@@ -11,12 +11,11 @@
 @WebServlet(urlPatterns = "/list-todos.do")
 public class ListTodoServlet extends HttpServlet {
 
-	private TodoService todoService = new TodoService();
+    private final TodoService todoService = new TodoService();
 
-	protected void doGet(HttpServletRequest request,
-			HttpServletResponse response) throws ServletException, IOException {
-		request.setAttribute("todos", todoService.retrieveTodos());
-		request.getRequestDispatcher("/WEB-INF/views/list-todos.jsp").forward(
-				request, response);
-	}
+    protected void doGet(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+        request.setAttribute("todos", todoService.retrieveTodos());
+        request.getRequestDispatcher("/WEB-INF/views/list-todos.jsp").forward(request, response);
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/com/in28minutes/todo/Todo.java b/src/main/java/com/in28minutes/todo/Todo.java
index 296d246..138e1b2 100644
--- a/src/main/java/com/in28minutes/todo/Todo.java
+++ b/src/main/java/com/in28minutes/todo/Todo.java
@@ -1,59 +1,56 @@
 package com.in28minutes.todo;
 
 public class Todo {
-	private String name;
-	private String category;
-
-	public Todo(String name, String category) {
-		super();
-		this.name = name;
-		this.category = category;
-	}
-
-	public String getName() {
-		return name;
-	}
-
-	public void setName(String name) {
-		this.name = name;
-	}
-
-	public String getCategory() {
-		return category;
-	}
-
-	public void setCategory(String category) {
-		this.category = category;
-	}
-
-	@Override
-	public String toString() {
-		return String.format("Todo [name=%s, category=%s]", name, category);
-	}
-
-	@Override
-	public int hashCode() {
-		final int prime = 31;
-		int result = 1;
-		result = prime * result + ((name == null) ? 0 : name.hashCode());
-		return result;
-	}
-
-	@Override
-	public boolean equals(Object obj) {
-		if (this == obj)
-			return true;
-		if (obj == null)
-			return false;
-		if (getClass() != obj.getClass())
-			return false;
-		Todo other = (Todo) obj;
-		if (name == null) {
-			if (other.name != null)
-				return false;
-		} else if (!name.equals(other.name))
-			return false;
-		return true;
+    private String name;
+    private String category;
+
+    public Todo(String name, String category) {
+        super();
+        this.name = name;
+        this.category = category;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getCategory() {
+        return category;
+    }
+
+    public void setCategory(String category) {
+        this.category = category;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("Todo [name=%s, category=%s]", name, category);
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Todo other = (Todo) obj;
+        if (name == null) {
+			return other.name == null;
+        } else return name.equals(other.name);
 	}
 
 }
diff --git a/src/main/java/com/in28minutes/todo/TodoService.java b/src/main/java/com/in28minutes/todo/TodoService.java
index a6039d4..60f45f5 100644
--- a/src/main/java/com/in28minutes/todo/TodoService.java
+++ b/src/main/java/com/in28minutes/todo/TodoService.java
@@ -4,23 +4,24 @@
 import java.util.List;
 
 public class TodoService {
-	private static List<Todo> todos = new ArrayList<Todo>();
-	static {
-		todos.add(new Todo("Learn Web Application Development", "Study"));
-		todos.add(new Todo("Learn Spring MVC", "Study"));
-		todos.add(new Todo("Learn Spring Rest Services", "Study"));
-	}
+    private static final List<Todo> todos = new ArrayList<>();
 
-	public List<Todo> retrieveTodos() {
-		return todos;
-	}
+    static {
+        todos.add(new Todo("Learn Web Application Development", "Study"));
+        todos.add(new Todo("Learn Spring MVC", "Study"));
+        todos.add(new Todo("Learn Spring Rest Services", "Study"));
+    }
 
-	public void addTodo(Todo todo) {
-		todos.add(todo);
-	}
+    public List<Todo> retrieveTodos() {
+        return todos;
+    }
 
-	public void deleteTodo(Todo todo) {
-		todos.remove(todo);
-	}
+    public void addTodo(Todo todo) {
+        todos.add(todo);
+    }
+
+    public void deleteTodo(Todo todo) {
+        todos.remove(todo);
+    }
 
 }