Spring Boot

·         Spring is the most popular application development framework for enterprise Java. Spring Framework creates high performing, easily testable, and reusable code.

·         Spring is lightweight when it comes to size and transparency. The basic version of Spring framework is around 2MB

        ·                  Spring framework targets to make J2EE development easier to use and promotes                  good programming practices by enabling a POJO-based programming model. (POJO            - Plain Old Java Object).

Benefits of Using the Spring Framework

Following is the list of few of the great benefits of using Spring Framework −

·        Spring enables developers to develop enterprise-class applications using POJOs. The benefit of using only POJOs is that you do not need an EJB container product such as an application server but you have the option of using only a robust servlet container such as Tomcat or some commercial product.

·        Spring is organized in a modular fashion. Even though the number of packages and classes are substantial, you have to worry only about the ones you need and ignore the rest.

·        Spring does not reinvent the wheel, instead it truly makes use of some of the existing technologies like several ORM frameworks, logging frameworks, JEE, Quartz and JDK timers, and other view technologies.

·        Testing an application written with Spring is simple because environment-dependent code is moved into this framework. Furthermore, by using JavaBeanstyle POJOs, it becomes easier to use dependency injection for injecting test data.

·        Spring's web framework is a well-designed web MVC framework, which provides a great alternative to web frameworks such as Struts or other over-engineered or less popular web frameworks.

·        Spring provides a convenient API to translate technology-specific exceptions (thrown by JDBC, Hibernate, or JDO, for example) into consistent, unchecked exceptions.

·        Lightweight IoC containers tend to be lightweight, especially when compared to EJB containers, for example. This is beneficial for developing and deploying applications on computers with limited memory and CPU resources.

·        Spring provides a consistent transaction management interface that can scale down to a local transaction (using a single database, for example) and scale up to global transactions (using JTA, for example).

Dependency Injection (DI) - Let's look at these two words separately. Here the dependency part translates into an association between two classes. For example, class A is dependent of class B. Now, let's look at the second part, injection. All this means is, class B will get injected into class A by the Inversion of Control (IoC). The Inversion of Control (IoC) is a general concept, and it can be expressed in many different ways. Dependency Injection is merely one concrete example of Inversion of Control.

 

Aspect Oriented Programming (AOP) - The functions that span multiple points of an application are called cross-cutting concerns and these cross-cutting concerns are conceptually separate from the application's business logic. There are various common good examples of aspects including logging, declarative transactions, security, caching, etc.

 

However, Spring is modular, allowing you to pick and choose which modules are applicable to you, without having to bring in the rest. The Spring Framework provides about 20 modules which can be used based on an application requirement.

Data Access/Integration

·        The JDBC module provides a JDBC-abstraction layer that removes the need for tedious JDBC related coding.

·        The ORM module provides integration layers for popular object-relational mapping APIs, including JPA, JDO, Hibernate, and iBatis.

·        The OXM module provides an abstraction layer that supports Object/XML mapping implementations for JAXB, Castor, XMLBeans, JiBX and XStream.

·        The Java Messaging Service JMS module contains features for producing and consuming messages.

·        The Transaction module supports programmatic and declarative transaction management for classes that implement special interfaces and for all your POJOs.

Web

·        The Web module provides basic web-oriented integration features such as multipart file-upload functionality and the initialization of the IoC container using servlet listeners and a web-oriented application context.

·        The Web-MVC module contains Spring's Model-View-Controller (MVC) implementation for web applications.

·        The Web-Socket module provides support for WebSocket-based, two-way communication between the client and the server in web applications.

·        The Web-Portlet module provides the MVC implementation to be used in a portlet environment and mirrors the functionality of Web-Servlet module.

Miscellaneous

·        The AOP module provides an aspect-oriented programming implementation allowing you to define method-interceptors and point cuts to cleanly decouple code that implements functionality that should be separated.

·        The Aspects module provides integration with AspectJ, which is again a powerful and mature AOP framework.

·        The Instrumentation module provides class instrumentation support and class loader implementations to be used in certain application servers.

·        The Messaging module provides support for STOMP as the Web Socket sub-protocol to use in applications. It also supports an annotation programming model for routing and processing STOMP messages from Web Socket clients.

·        The Test module supports the testing of Spring components with JUnit or TestNG frameworks.

Core Container

·        The Core module provides the fundamental parts of the framework, including the IoC and Dependency Injection features.

·        The Bean module provides Bean Factory, which is a sophisticated implementation of the factory pattern.

·        The Context module builds on the solid base provided by the Core and Beans modules and it is a medium to access any objects defined and configured. The Application Context interface is the focal point of the Context module.

·        The SpEL module provides a powerful expression language for querying and manipulating an object graph at runtime.

 

Code Ex :

Here is the content of HelloWorld.java file −

               package com.tutorialspoint;

               public class HelloWorld {

                               private String message;

                              public void setMessage(String message){

                                              this.message  = message;

                              }

                              public void getMessage(){

                                              System.out.println("Your Message : " + message);

                              }

               }

Following is the content of the second file MainApp.java −

               package com.tutorialspoint;

               import org.springframework.context.ApplicationContext;

               import org.springframework.context.support.ClassPathXmlApplicationContext;

               public class MainApp {

                               public static void main(String[] args) {

                               ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

                               HelloWorld obj = (HelloWorld) context.getBean("helloWorld");

                              obj.getMessage();

                              }

               }