Spring Framework

Spring uses various new techniques such as Aspect-Oriented Programming (AOP), Plain Old Java Object (POJO), and dependency injection (DI), to develop enterprise applications, thereby removing the complexities involved while developing enterprise applications using EJB

Spring mainly focuses on providing various ways to help you manage your business objects

The Spring framework can be considered as a collection of sub-frameworks, also called layers, such as Spring AOP, Spring Object-Relational Mapping (Spring ORM). Spring Web Flow, and Spring Web MVC

Spring Framework Features

• Lightweight

  The Spring Framework is very lightweight with respect to its size and functionality. It is due to its POJO implementation which doesn’t force to inherit any class or implement any interfaces.

• Aspect Oriented Programming(AOP)

  It is an important part of Spring Framework. Aspect Oriented Programming is used for separating cross-cutting concerns (for example logging, security etc.) from the business logic of the application.

• Transaction Management

  This framework provides Java Transaction API (JTA) for global transactions managed by an application server and local transactions managed by using the JDBC, Hibernate, Java Data Objects (JDO), or other data access APIs.

• IoC container

  Refers to the core container that uses the DI or IoC pattern to implicitly provide an object reference in a class during runtime, help manage the lifecycle and configurations of application objects.

• Dependency Injection

  Dependency Injection is a feature of Spring Framework allows you to develop loosely coupled applications. Therefore, the unit testing of these loosely coupled applications becomes easier.

    //without DI
    public class TextEditor {
        private SpellChecker spellChecker;
        public TextEditor() {
            spellChecker = new SpellChecker();
        }
    }
    //with DI
    public class TextEditor {
        private SpellChecker spellChecker;
            public TextEditor(SpellChecker spellChecker) {
            this.spellChecker = spellChecker;
        }
    }
  

  Spring Framework Architecture

• Spring Core Module

  Provides the IoC container, there are two types of implementations of the Spring container, namely, bean factory and application context. The Bean factory container allows you to decouple the configuration and specification of dependencies from program logic. In the Spring framework, the Bean factory acts as a central IoC container that is responsible for instantiating application objects. It also configures and assembles the dependencies between these objects.

• Spring AOP Module

  Spring AOP module allows you to implement concerns or aspects in a Spring application in Spring AOP, the aspects are the regular Spring beans or regular classes annotated with @Aspect annotation.

• Spring ORM Module

  Used for accessing data from databases in an application. It provides APIs for manipulating databases with DAO, JDO, Hibernate, and iBatis.

• Spring Web MVC Module

  It implements the MVC architecture for creating Web applications.

• Spring Web Flow Module

  The Spring Web Flow helps in defining XML file or Java Class that manages the workflow between different pages of a Web application.

• Spring Web DAO Module

  Provides DAO support by using data access technologies such as JDBC, Hibernate, or JDO. This module introduces a JDBC abstraction layer by eliminating the need for providing tedious JDBC coding.

• Spring Application Context Module

  Based on the Core module, this module derives its feature from the org.springframework.beans package and also supports functionalities such as internationalization, validation, event propagation, and resource loading. The Application context implements MessageSource interface and provides the messaging functionality to an application.

Spring MVC

In Spring MVC, when a Request is generated from the browser, it first goes to the DispatcherServlet class (Front Controller), which dispatches the request to a Controller (SimpleFormController class or AbstractWizardformController class) using a set of Handler Mappings. The controller extracts and processes the information embedded in a request and sends the result to the DispatcherServlet class in the form of the model object. Finally, the DispatcherServlet class uses ViewResolver classes to send the results to a View, which displays these results to the users.