Spring Boot


Spring Boot

  • Description
  • Curriculum

Introducing to Spring Boot

It is a completely new project from Pivotal Team (The Spring Team). Spring Boot is their latest innovation to keep up to date with the changing technology needs. The primary motivation behind developing Spring Boot is to simplify the process for configuring and deploying the spring applications. This Spring Boot Tutorial gives complete introduction about Spring Boot.

Spring Boot offers a new paradigm for developing Spring applications with minimal friction. With Spring Boot, you’ll be able to develop Spring applications with more agility and be able to focus on addressing your application’s functionality needs with minimal (or possibly no) thought of configuring Spring itself. It uses completely new development model to make Java Development very easy by avoiding some tedious development steps and boilerplate code and configuration.

Spring Boot makes it easy to create stand-alone, production-grade Spring based Applications that you can “just run”. We take an opinionated view of the spring platform and third-party libraries so you can get started with minimum fuss. Most Spring Boot applications need very little Spring configuration.

You can use Spring Boot to create Java applications that can be started using java -jar or more traditional war deployments. We also provide a command line tool that runs “spring scripts”.

What is spring boot?

In this Spring Boot Tutorial, first of all Spring Boot is not a framework, it is a way to ease to create stand-alone application with minimal or zero configurations. It is approach to develop spring based application with very less configuration. It provides defaults for code and annotation configuration to quick start new spring projects within no time. Spring Boot leverages existing spring projects as well as Third party projects to develop production ready applications. It provides a set of Starter Pom’s or gradle build files which one can use to add required dependencies and also facilitate auto configuration.

Spring Boot automatically configures required classes depending on the libraries on its classpath. Suppose your application want to interact with DB, if there are Spring Data libraries on class path then it automatically sets up connection to DB along with the Data Source class.

Spring Boot Primary Goals

Let’s see Spring Boot primary goals are following in this Spring Boot Tutorial:

  • Provide a radically faster and widely accessible getting started experience for all Spring development.
  • Be opinionated out of the box, but get out of the way quickly as requirements start to diverge from the defaults.
  • Provide a range of non-functional features that are common to large classes of projects (e.g. embedded servers, security, metrics, health checks, externalized configuration).
  • Absolutely no code generation and no requirement for XML configuration, to avoid XML Configuration completely
  • To avoid defining more Annotation Configuration(It combined some existing Spring Framework Annotations to a simple and single Annotation)
  • Spring Boot avoid writing lots of import statements
  • To provide some defaults to quick start new projects within no time.

Why New Project Need Spring Boot?

Suppose we are developing one of Hello World application in Spring Framework, for that there is only one item is specific to developing the Hello World functionality: the controller. The rest of it is generic boilerplate that you’d need for any web application developed with Spring. But if all Spring web applications need it, why should you have to provide it? So there are following things any new project need Spring Boot.

  • To ease the Java-based applications Development, Unit Test and Integration Test Process.
  • To reduce Development, Unit Test and Integration Test time by providing some defaults.
  • Spring Boot increase Productivity.
  • When we talk about defaults, Spring Boot has its own opinions. If you are not specifying the details, it will use its own default configurations. If you want persistence, but don’t specify anything else in your POM file, then Spring Boot configures Hibernate as a JPA provider with an HSQLDB database.
  • To provide bunch of non-functional features/solutions that are very much common to large scale projects (e.g. embedded servers, security, metrics, health checks, externalized configuration).

What Spring Boot Isn’t?

As above mention Spring Boot is not a framework to write applications, it helps you to develop and build, package and deploy application with minimal configuration or zero configuration.

It is not an application server. But it’s the embedded servlet container that provides application server functionality, not Spring Boot itself.

Similarly, Spring Boot doesn’t implement any enterprise Java specifications such as JPA or JMS. For example, Spring Boot doesn’t implement JPA, but it does support JPA by auto-configuring the appropriate beans for a JPA implementation (such as Hibernate)

Finally, Spring Boot doesn’t employ any form of code generation to accomplish its magic. Instead, it leverages conditional configuration features from Spring 4, along with transitive dependency resolution offered by Maven and Gradle, to automatically configure beans in the Spring application context.

In short, at its heart, Spring Boot is just Spring.
Future Spring projects would not have any XML configurations as part of it, everything will be handled by the project Spring Boot.

Pros/Cons of Spring Boot

Pros of Spring Boot:

  • It is very easy to develop Spring Based applications with Java or Groovy.
  • Spring Boot reduces lots of development time and increases productivity.
  • It avoids writing lots of boilerplate Code, Annotations and XML Configuration.
  • It is very easy to integrate Spring Boot Application with its Spring Ecosystem like Spring JDBC, Spring ORM, Spring Data, Spring Security etc.
  • Spring Boot follows “Opinionated Defaults Configuration” Approach to reduce Developer effort
  • It provides Embedded HTTP servers like Tomcat, Jetty etc. to develop and test our web applications very easily.
  • It provides CLI (Command Line Interface) tool to develop and test Spring Boot (Java or Groovy) Applications from command prompt very easily and quickly.
  • Spring Boot provides lots of plugins to develop and test Spring Boot Applications very easily using Build Tools like Maven and Gradle
  • It provides lots of plugins to work with embedded and in-memory Databases very easily.

Limitation of Spring Boot:

It is very tough and time consuming process to convert existing or legacy Spring Framework projects into Spring Boot Applications. It is applicable only for brand new/Greenfield Spring Projects.

Spring boot releases

Latest Release: Spring Boot 1.3.3 and 1.4.0 available now. You require minimum Spring Framework 4.2.2 for this version.

Limitation of Spring Boot:

It is very tough and time consuming process to convert existing or legacy Spring Framework projects into Spring Boot Applications. It is applicable only for brand new/Greenfield Spring Projects.

  • Executable JAR Layout
  • Startup error improvements
  • Hibernate 5
  • Spring Framework 4.3
  • Third Party Library
  • Custom JSON Serializer and Deserializer
  • New auto-configuration support
    • Couchbase
    • Neo4j
    • Narayana transactional manager
    • Caffeine Cache
  • Actuator improvements
  • Testing improvements

Getting started with Spring Boot

Ultimately, a Spring Boot project is just a regular Spring project that happens to leverage Spring Boot starters and auto-configuration. To Start Opinionated Approach to create Spring Boot Applications, The Spring Team (The Pivotal Team) has provided the following three approaches.

  • Using Spring Boot CLI Tool
  • Spring STS IDE
  • Using Spring Initializr (Website http://start.spring.io/)

We can develop two flavors of Spring-Based Applications using Spring Boot

  • Java-Based Applications
  • Groovy Applications

We can use Spring Boot CLI or Spring STS IDE or Spring Initializr Website to develop Spring Boot Groovy Applications. However, we can use Spring STS IDE or Spring Initializr Website to develop Spring Boot Java Applications.

Anyhow, Groovy is also JVM language almost similar to Java Language. We can combine both Groovy and Java into one Project. Because like Java files, Groovy files are finally compiled into *.class files only. Both *.groovy and *.java files are converted to *.class file (Same byte code format).

Spring Boot Framework Programming model is inspired by Groovy Programming model. It internally uses some Groovy based techniques and tools to provide default imports and configuration.

Spring Boot Framework also combined existing Spring Framework annotations into some simple or single annotations. We will explore those annotations one by one in coming posts with some real-time examples.

Spring Boot Framework drastically changes Spring-Java Based Applications Programming model into new Programming model. As of now, Spring Boot is at initial stage only but future is all about Spring Boot only.

Spring Boot CLI

It is the easiest and quickest way to start using the Spring Boot. It is a command line tool used for executing the groovy scripts. In summary, you can install this tool by following these steps:

1. Download the binary distributions for this project from here. Spring Boot CLI requires Java JDK v1.6 or above in order to run. Groovy v2.1 is packaged as part of this distribution, and therefore does not need to be installed (any existing Groovy installation is ignored)

2. If you unpack the zip file, you will find spring.bat which will check the all the settings. This script can be found under the directory /bin.

Hello World example using spring boot

We can develop two flavors of Spring-Based Applications using Spring Boot.

  • Groovy Applications
  • Java-Based Applications

Groovy Applications:

Let’s develop a simple “Hello World!” web application. Create the app.groovy with the following lines of code. Here we are going explain same example from Spring Boot documentation.

You can invoke the http://localhost:8080 in your browser and you will see the result “Hello World!”.The above command can invoke the application and run it in the web server.

Spring Boot does this by dynamically adding key annotations to your code and leveraging Groovy Grape to pull down needed libraries to make the app run. If any dependencies are required like web server, etc. can be resolved by the Spring Boot itself.

Java-Based Applications

Let’s develop a simple “Hello World!” web application in Java that highlights some of Spring Boot’s key features. We’ll use Maven to build this project since most IDEs support it.

If you are Java developer you can use start.spring.io to generate a basic project.


Starters are a set of convenient dependency descriptors that you can include in your application. The starters contain a lot of the dependencies that you need to get a project up and running quickly and with a consistent, supported set of managed transitive dependencies.

The starter POMs are convenient dependency descriptors that can be added to your application’s Maven. In simple words, if you are developing a project that uses Spring Batch for batch processing, you just have to include spring-boot-starter-batch that will import all the required dependencies for the Spring Batch application. This reduces the burden of searching and configuring all the dependencies required for a framework.

List of Starters

Spring offers wide range of started POMs that can be used in your application. Here is the list of started POMs mention in this Spring Boot Tutorial.

Name Description
spring-boot-starter-test Starter for testing Spring Boot applications with libraries including JUnit, Hamcrest and Mockito
spring-boot-starter-mobile Starter for building web applications using Spring Mobile
spring-boot-starter-social-twitter Starter for using Spring Social Twitter
spring-boot-starter-cache Starter for using Spring Framework’s caching support
spring-boot-starter-activemq Starter for JMS messaging using Apache ActiveMQ
spring-boot-starter-jta-atomikos Starter for JTA transactions using Atomikos
spring-boot-starter-aop Starter for aspect-oriented programming with Spring AOP and AspectJ
spring-boot-starter-web Starter for building web, including RESTful, applications using Spring MVC. Uses Tomcat as the default embedded container
spring-boot-starter-data-elasticsearch Starter for using Elasticsearch search and analytics engine and Spring Data Elasticsearch
spring-boot-starter-jdbc Starter for using JDBC with the Tomcat JDBC connection pool
spring-boot-starter-batch Starter for using Spring Batch, including HSQLDB in-memory database
spring-boot-starter-social-facebook Starter for using Spring Social Facebook
spring-boot-starter-web-services Starter for using Spring Web Services
spring-boot-starter-jta-narayana Spring Boot Narayana JTA Starter
spring-boot-starter-thymeleaf Starter for building MVC web applications using Thymeleaf views
spring-boot-starter-mail Starter for using Java Mail and Spring Framework’s email sending support
spring-boot-starter-jta-bitronix Starter for JTA transactions using Bitronix
spring-boot-starter-data-mongodb Starter for using MongoDB document-oriented database and Spring Data MongoDB
spring-boot-starter-validation Starter for using Java Bean Validation with Hibernate Validator
spring-boot-starter-jooq Starter for using jOOQ to access SQL databases. An alternative to spring-boot-starter-data-jpa or spring-boot-starter-jdbc
spring-boot-starter-redis Starter for using Redis key-value data store with Spring Data Redis and the Jedis client. Deprecated as of 1.4 in favor of spring-boot-starter-data-redis
spring-boot-starter-data-cassandra Starter for using Cassandra distributed database and Spring Data Cassandra
spring-boot-starter-hateoas Starter for building hypermedia-based RESTful web application with Spring MVC and Spring HATEOAS
spring-boot-starter-integration Starter for using Spring Integration
spring-boot-starter-data-solr Starter for using the Apache Solr search platform with Spring Data Solr
spring-boot-starter-freemarker Starter for building MVC web applications using Freemarker views
spring-boot-starter-jersey Starter for building RESTful web applications using JAX-RS and Jersey. An alternative to spring-boot-starter-web
spring-boot-starter Core starter, including auto-configuration support, logging and YAML
spring-boot-starter-data-couchbase Starter for using Couchbase document-oriented database and Spring Data Couchbase
spring-boot-starter-artemis Starter for JMS messaging using Apache Artemis
spring-boot-starter-cloud-connectors Starter for using Spring Cloud Connectors which simplifies connecting to services in cloud platforms like Cloud Foundry and Heroku
spring-boot-starter-social-linkedin Stater for using Spring Social LinkedIn
spring-boot-starter-velocity Starter for building MVC web applications using Velocity views. Deprecated since 1.4
spring-boot-starter-data-rest Starter for exposing Spring Data repositories over REST using Spring Data REST
spring-boot-starter-data-gemfire Starter for using GemFire distributed data store and Spring Data GemFire
spring-boot-starter-groovy-templates Starter for building MVC web applications using Groovy Templates views
spring-boot-starter-amqp Starter for using Spring AMQP and Rabbit MQ
spring-boot-starter-hornetq Starter for JMS messaging using HornetQ. Deprecated as of 1.4 in favor of spring-boot-starter-artemis
spring-boot-starter-ws Starter for using Spring Web Services. Deprecated as of 1.4 in favor of spring-boot-starter-web-services
spring-boot-starter-security Starter for using Spring Security
spring-boot-starter-data-redis Starter for using Redis key-value data store with Spring Data Redis and the Jedis client
spring-boot-starter-websocket Starter for building WebSocket applications using Spring Framework’s WebSocket support
spring-boot-starter-mustache Starter for building MVC web applications using Mustache views
spring-boot-starter-data-neo4j Starter for using Neo4j graph database and Spring Data Neo4j
spring-boot-starter-data-jpa Starter for using Spring Data JPA with Hibernate

Servlet containers Support

The following embedded servlet containers are supported out of the box.

Name Servlet Version Java Version
Tomcat 8 3.1 Java 7+
Tomcat 7 3.0 Java 6+
Jetty 9 3.1 Java 7+
Jetty 8 3.0 Java 6+
Undertow 1.1 3.1 Java 7+

You can also deploy Spring Boot applications to any Servlet 3.0+ compatible container.

Template engines Support

Spring Boot includes auto-configuration support for the following templating engines mention in this Spring Boot Tutorial.

  • FreeMarker
  • Groovy
  • Thymeleaf
  • Velocity (deprecated in 1.4)
  • Mustache

JSPs should be avoided if possible; there are several known limitations when using them with embedded servlet containers. If you are using any of the above template engines, spring boot will automatically pick the templates from src/main/resources/templates.

Caching SupportC

The Spring Framework provides support for transparently adding caching to an application. At its core, the abstraction applies caching to methods, reducing thus the number of executions based on the information available in the cache. The caching logic is applied transparently, without any interference to the invoker. Let;s see the code as mention below here Spring Boot Tutorial.

In this Spring Boot Tutorial, I have mentioned following list that Spring Boot tries to detect the following providers (in this order):

  • Generic
  • JCache (JSR-107)
  • EhCache 2.x
  • Hazelcast
  • Infinispan
  • Couchbase
  • Redis
  • Caffeine
  • Guava
  • Simple

Spring Boot & Spring MVC

Spring Boot is well suited for web application development. You can easily create a self-contained HTTP server using embedded Tomcat, Jetty, or Undertow. Most web applications will use the spring-boot-starter-web module to get up and running quickly.

Spring MVC lets you create special @Controller or @RestController beans to handle incoming HTTP requests. Methods in your controller are mapped to HTTP using @RequestMapping annotations.

Spring MVC auto-configuration

Spring Boot provides auto-configuration for Spring MVC that works well with most applications.The auto-configuration adds the following features on top of Spring’s defaults:

  • Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
  • Support for serving static resources, including support for WebJars (see below).
  • Automatic registration of Converter, GenericConverter, Formatter beans.
  • Support for HttpMessageConverters (see below).
  • Automatic registration of MessageCodesResolver (see below).
  • Static index.html support.
  • Custom Favicon support.
  • Automatic use of a ConfigurableWebBindingInitializer bean