Spring Boot is a project that is built on the top of the Spring Framework. It provides an easier and faster way to set up, configure, and run both simple and web-based applications.

It is a Spring module that provides the RAD (Rapid Application Development) feature to the Spring Framework. It is used to create a stand-alone Spring-based application that you can just run because it needs minimal Spring configuration.

In short, Spring Boot is the combination of Spring Framework and Embedded Servers.

In Spring Boot, there is no requirement for XML configuration (deployment descriptor). It uses convention over configuration software design paradigm that means it decreases the effort of the developer.

We can use Spring STS IDE or Spring Initializr to develop Spring Boot Java applications.

Why should we use Spring Boot Framework?

We should use Spring Boot Framework because:

The dependency injection approach is used in Spring Boot.
It contains powerful database transaction management capabilities.
It simplifies integration with other Java frameworks like JPA/Hibernate ORM, Struts, etc.
It reduces the cost and development time of the application.

Along with the Spring Boot Framework, many other Spring sister projects help to build applications addressing modern business needs. There are the following Spring sister projects are as follows:

Spring Data: It simplifies data access from the relational and NoSQL databases.
Spring Batch: It provides powerful batch processing.
Spring Security: It is a security framework that provides robust security to applications.
Spring Social: It supports integration with social networking like LinkedIn.
Spring Integration: It is an implementation of Enterprise Integration Patterns. It facilitates integration with other enterprise applications using lightweight messaging and declarative adapters.

Advantages of Spring Boot

It creates stand-alone Spring applications that can be started using Java -jar.
It tests web applications easily with the help of different Embedded HTTP servers such as Tomcat, Jetty, etc. We don’t need to deploy WAR files.
It provides opinionated ‘starter‘ POMs to simplify our Maven configuration.
It provides production-ready features such as metrics, health checks, and externalized configuration.
There is no requirement for XML configuration.
It offers a CLI tool for developing and testing the Spring Boot application.
It offers the number of plug-ins.
It also minimizes writing multiple boilerplate codes (the code that has to be included in many places with little or no alteration), XML configuration, and annotations.
It increases productivity and reduces development time.

Limitations of Spring Boot

Spring Boot can use dependencies that are not going to be used in the application. These dependencies increase the size of the application.

Goals of Spring Boot

The main goal of Spring Boot is to reduce development, unit test, and integration test time.

Provides Opinionated Development approach
Avoids defining more Annotation Configuration
Avoids writing lots of import statements
Avoids XML Configuration.

By providing or avoiding the above points, Spring Boot Framework reduces Development time, Developer Effort, and increases productivity.

Prerequisite of Spring Boot

To create a Spring Boot application, following are the prerequisites. In this tutorial, we will use Spring Tool Suite (STS) IDE.

Java 1.8
Maven 3.0+
Spring Framework 5.0.0.BUILD-SNAPSHOT
An IDE (Spring Tool Suite) is recommended.

Spring Boot Features

Web Development
SpringApplication
Application events and listeners
Admin features
Externalized Configuration
Properties Files
YAML Support
Type-safe Configuration
Logging
Security

Web Development

It is a well-suited Spring module for web application development. We can easily create a self-contained HTTP application that uses embedded servers like Tomcat, Jetty, or Undertow. We can use the spring-boot-starter-web module to start and run the application quickly.

SpringApplication

The SpringApplication is a class that provides a convenient way to bootstrap a Spring application. It can be started from the main method. We can call the application just by calling a static run() method.

publicstatic void main(String[] args)

{

run(ClassName.class, args);

}

Application Events and Listeners

Spring Boot uses events to handle the variety of tasks. It allows us to create factories file that is used to add listeners. We can refer it to using the ApplicationListener key.

Always create factories file in META-INF folder like META-INF/spring.factories.

Admin Support

Spring Boot provides the facility to enable admin-related features for the application. It is used to access and manage applications remotely. We can enable it in the Spring Boot application by using spring.application.admin.enabled property.

Externalized Configuration

Spring Boot allows us to externalize our configuration so that we can work with the same application in different environments. The application uses YAML files to externalize configuration.

Properties Files

Spring Boot provides a rich set of Application Properties. So, we can use that in the properties file of our project. The properties file is used to set properties like server-port =8082 and many others. It helps to organize application properties.

YAML Support

It provides a convenient way of specifying the hierarchical configuration. It is a superset of JSON. The SpringApplication class automatically supports YAML. It is an alternative of properties file.

Type-safe Configuration

The strong type-safe configuration is provided to govern and validate the configuration of the application. Application configuration is always a crucial task which should be type-safe. We can also use annotation provided by this library.

Logging

Spring Boot uses Common logging for all internal logging. Logging dependencies are managed by default. We should not change logging dependencies if no customization is needed.

Security

Spring Boot applications are spring bases web applications. So, it is secure by default with basic authentication on all HTTP endpoints. A rich set of Endpoints is available to develop a secure Spring Boot application.

Spring Boot Version

The latest version of Spring Boot is 2.0. It introduces a lot of new features along with some modifications and replacement.

Spring Boot 2.0

Let’s have a sneak peek at Spring Boot 2.0.

What’s New
Infrastructure Upgrade
Spring Framework 5
What’s Changed
Configuration Properties
Gradle Plugin
Actuators endpoints
What’s Evolving
Security
Metrics

The pivotal team has upgraded the infrastructure in which the following tools are involved:

Supports Java 8 or above versions
Supports Apache Tomcat 8 or above versions
Supports Thymeleaf 3
Supports Hibernate 5.2

In Spring Framework 5, the Pivotal team upgraded the following:

Reactive Spring
1. Servlet stack
  1. Servlet Container
  2. Servlet API
  3. Spring MVC
2. Reactive Stack
  1. Netty, Servlet 3.1, Undertow
  2. Reactive HTTP Layer
  3. Spring WebFlux
Functional API
Kotlin Support

The latest version of Spring Boot is 2.2.1. This release of Spring Boot includes 110 fixes, dependency upgrades, and improvements.

In the Spring Boot v2.2.1, the annotation @ConfigurationProperties scanning is now disabled by default. We need to be explicitly opted into by adding the @ConfigurationPropertiesScan annotation.

New Features

Support constructor binding for property nested inside a JavaBean
Add config property for CodecConfigurer.maxInMemorySize in WebFlux
Make test slices’ type exclude filters public
Support amqps:// URIs in spring.rabbitmq.addresses

Dependency upgrades

Some dependencies have been upgraded in Spring Boot v2.2.1 are as follows:

Mongodb 3.11.2
Spring Security 5.2.1.RELEASE
Slf4j 1.7.29
Spring Hateoas 1.0.1.RELEASE
Hibernate Validator 6.0.18.Final
Hibernate 5.4.8.Final
Jetty 9.4.22.v20191022
Spring Framework 5.2.1
Spring AMQP 2.2.1
H2 1.4.200
Spring Security 5.2
Spring Batch 4.2

Some important and widely used third-party dependencies are upgraded in this release are as follows:

Micrometer 1.3.1
Flyway 6.0.7
Elasticsearch 6.8.4
JUnit 5.5
Jackson 2.10

Performance Improvements

In Spring Boot 2.2.1 the following performance has been improved:

Lazy Initialization

In Spring Boot 2.2.1, we can enable global lazy initialization by using the property spring.main.lazy-initialization property. It reduces the application startup time.

Java 13 Support

Spring Boot 2.2.1 now supports the latest version of Java that is Java 13.

Immutable Binding

In the newer version of Spring Boot, Configuration properties support constructor-based binding. The class annotates with @ConfigurationProperties annotation is to be immutable. It can be enabled by adding an annotation @ConfugurationProperties to a class or one of its constructors with @ConstructorBinding.

RSocket Support

It is a part of Spring Security. RSocket integration is auto-configured when an application finds spring-security-rsocket is present on the classpath.

Deprecations in Spring Boot 2.2

The property logging.file has renamed to logging.file.name.
The property logging.path has renamed to logging.file.path.
The server.connection-timeout property has been deprecated in favor of server-specific properties.
Joda time support is deprecated in favor of java.time.

The following improvements are made in the Spring Boot 2.2.1

Java: Spring Boot 2.2.1
Spring Framework 5.2: This release of Spring Boot upgrades to Spring Framework to 5.2.
JMX is disabled: In this version, JMX is not enabled by default. We can enable it by using the property jmx.enabled=true. If you are using the IDE feature to monitor your application, we need to enable it.
Fork enabled by default: Spring Boot application that ran by Maven Plugin is now forked by default.
JUnit 5: Spring Boot v2.2.1 provides JUnit 5 by default. JUnit 5’s vintage engine is also included by default that supports existing JUnit 4-based test classes. We can also use JUnit 4 and JUnit 5 based test classes in the same module.
AssertJ 3.12: This release of Spring Boot upgrades to AssertJ 3.12. It contains a breaking API changes for assertions related to Iterator.
Hibernate Dialect: In the newer version of Spring Boot, Hibernate chose the dialect to use rather than applying a default dialect based on the detected database.
Gradle Requirements: The latest version of Spring Boot requires Gradle 4.10.

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Java Fundamentals
Introduction to Java Basics
Features of Java
Various components of Java language
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Installation and IDE’s for Java Programming Language

Installation of Java
Setting up of Eclipse IDE
Components of Java Program
Editors and IDEs used for Java Programming
Writing a Simple Java Program

Data Handling and Functions

Data types, Operations, Compilation process, Class files, Loops, Conditions
Using Loop Constructs
Arrays- Single Dimensional and Multi-Dimensional
Functions
Functions with Arguments

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Object Oriented Programming in Java
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String Handling –String Class
Java Packages

Exception Handling and Multi-Threading

Exception handling
Various Types of Exception Handling
Introduction to multi-threading in Java
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Synchronizing the thread

File Handling in Java

Input Output Streams
Java.io Package
File Handling in Java

Java Collections

Wrapper Classes and Inner Classes: Integer, Character, Boolean, Float etc
Applet Programs: How to write UI programs with Applet, Java.lang, Java.io, Java.util
Collections: ArrayList, Vector, HashSet, TreeSet, HashMap, HashTable

Java Database Connectivity (JDBC)

Introduction to SQL: Connect, Insert, Update, Delete, Select
Introduction to JDBC and Architecture of JDBC
Insert/Update/Delete/Select Operations using JDBC
Batch Processing Transaction
Management: Commit and Rollback

Java Enterprise Edition – Servlets

Introduction to J2EE
Client Server architecture
URL, Port Number, Request, Response
Need for servlets
Servlet fundamentals
Setting up a web project in Eclipse
Configuring and running the web app with servlets
GET and POST request in web application with demo
Servlet lifecycle
Servlets Continued
Session tracking and filter
Forward and include Servlet request dispatchers

Java Server Pages (JSP)

Fundamentals of Java Server Page
Writing a code using JSP
The architecture of JSP
JSP Continued
JSP elements: Scriptlets, expressions, declaration
JSP standard actions
JSP directives
Introduction to JavaBeans
ServletConfig and ServletContext
Servlet Chaining
Cookies Management
Session Management

Hibernate

Introduction to Hibernate
Introduction to ORM
ORM features
Hibernate as an ORM framework
Hibernate features
Setting up a project with Hibernate framework
Basic APIs needed to do CRUD operations with Hibernate
Hibernate Architecture

POJO (Plain Old Java Object)

POJO (Plain Old Java Object)
Persistent Objects
Lifecycle of Persistent Object

Spring

Introduction to Spring
Spring Fundamentals
Advanced Spring

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