Spring Boot Tutorial provides basic and advanced concepts of Spring Framework. Our Spring Boot Tutorial is designed for beginners and professionals both.

Spring Boot is a Spring module that provides the RAD (Rapid Application Development) feature to the Spring framework.

Our Spring Boot Tutorial includes all topics of Spring Boot such, as features, project, maven project, starter project wizard, Spring Initializr, CLI, applications, annotations, dependency management, properties, starters, Actuator, JPA, JDBC, etc.

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.

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• 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.

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

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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.

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.

• 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.

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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.

1. public static void main(String[] args)  
2. {    
3. SpringApplication.run(ClassName.class, args);    
4. }  

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.

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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.

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Before learning Spring Boot, you must have the basic knowledge of Spring Framework.

Our Spring Boot Tutorial is designed to help beginners and professionals.

We assure you that you will not find any problem with the Spring Boot Tutorial. But if there is any mistake, please post the problem in the contact form.

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

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

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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.

• 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

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

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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.

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• 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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Spring: Spring Framework is the most popular application development framework of Java. The main feature of the Spring Framework is dependency Injection or Inversion of Control (IoC). With the help of Spring Framework, we can develop a loosely coupled application. It is better to use if application type or characteristics are purely defined.

Spring Boot: Spring Boot is a module of Spring Framework. It allows us to build a stand-alone application with minimal or zero configurations. It is better to use if we want to develop a simple Spring-based application or RESTful services.

The primary comparison between Spring and Spring Boot are discussed below:

 Spring  : 

1) Spring Framework is a widely used Java EE framework for building applications. 

2)  It aims to simplify Java EE development that makes developers more productive. 

3) The primary feature of the Spring Framework is dependency injection. 

4) It helps to make things simpler by allowing us to develop loosely coupled applications. 

5) The developer writes a lot of code (boilerplate code) to do the minimal task. 

6) To test the Spring project, we need to set up the sever explicitly. 

7) It does not provide support for an in-memory database. 

8) Developers manually define dependencies for the Spring project in pom.xml. 

 Spring Boot :

1) Spring Boot Framework is widely used to develop REST APIs. 

2) It aims to shorten the code length and provide the easiest way to develop Web Applications. 

3) The primary feature of Spring Boot is Autoconfiguration. It automatically configures the classes based on the requirement. 

4) It helps to create a stand-alone application with less configuration. 

5)  It reduces boilerplate code. 

6) Spring Boot offers embedded server such as Jetty and Tomcat, etc.
7)  It offers several plugins for working with an embedded and in-memory database such as H2. 

8) Spring Boot comes with the concept of starter in pom.xml file that internally takes care of downloading      the dependencies JARs based on Spring Boot Requirement. 

Spring Boot: Spring Boot makes it easy to quickly bootstrap and start developing a Spring-based application. It avoids a lot of boilerplate code. It hides a lot of complexity behind the scene so that the developer can quickly get started and develop Spring-based applications easily.

Spring MVC: Spring MVC is a Web MVC Framework for building web applications. It contains a lot of configuration files for various capabilities. It is an HTTP oriented web application development framework.

Spring Boot and Spring MVC exist for different purposes. The primary comparison between Spring Boot and Spring MVC are discussed below:

 Spring Boot : 

1) Spring Boot is a module of Spring for packaging the Spring-based application with sensible defaults. 

2) It provides default configurations to build Spring-powered framework. 

3) There is no need to build configuration manually. 

4) There is no requirement for a deployment descriptor.

5) It avoids boilerplate code and wraps dependencies together in a single unit.

6) It reduces development time and increases productivity.

 Spring MVC : 

1) Spring MVC is a model view controller-based web framework under the Spring framework. 

2) It provides ready to use features for building a web application. 

3) It requires build configuration manually. 

4) A Deployment descriptor is required. 

5) It specifies each dependency separately. 

6) It takes more time to achieve the same.

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Spring Boot is a module of the Spring Framework. It is used to create stand-alone, production-grade Spring Based Applications with minimum efforts. It is developed on top of the core Spring Framework.

Spring Boot follows a layered architecture in which each layer communicates with the layer directly below or above (hierarchical structure) it.

Before understanding the Spring Boot Architecture, we must know the different layers and classes present in it. There are four layers in Spring Boot are as follows:

• Presentation Layer
• Business Layer
• Persistence Layer
• Database Layer

Presentation Layer: The presentation layer handles the HTTP requests, translates the JSON parameter to object, and authenticates the request and transfer it to the business layer. In short, it consists of views i.e., frontend part.

Business Layer: The business layer handles all the business logic. It consists of service classes and uses services provided by data access layers. It also performs authorization and validation.

Persistence Layer: The persistence layer contains all the storage logic and translates business objects from and to database rows.

Database Layer: In the database layer, CRUD (create, retrieve, update, delete) operations are performed.

• Now we have validator classes, view classes, and utility classes.
• Spring Boot uses all the modules of Spring-like Spring MVC, Spring Data, etc. The architecture of Spring Boot is the same as the architecture of Spring MVC, except one thing: there is no need for DAO and DAOImpl classes in Spring boot.
• Creates a data access layer and performs CRUD operation.
• The client makes the HTTP requests (PUT or GET).
• The request goes to the controller, and the controller maps that request and handles it. After that, it calls the service logic if required.
• In the service layer, all the business logic performs. It performs the logic on the data that is mapped to JPA with model classes.
• A JSP page is returned to the user if no error occurred.