Spring Tutorial 01 - Basic Concepts of Spring

What is Spring?

Spring is an open source, lightweight, application framework that is intended to help structure entire applications in a consistent manner, pulling together best of breed single-tier frameworks in a coherent architecture

Spring provides us below features.

• Complexity of solution
• Timeline
• Maintainability
• Familiarity with framework
• Community and Documentation
• Framework Licensing

Spring Architecture Diagram

• IoC Container
• Aspect-Oriented Programming Framework (AOP)
• Data access abstraction and JDBC simplifications
• Transaction Management
• MVC web framework
• Simplification for working with J2EE APIs such as JNDI, JTA, etc.
• Lightweight remoting, JMS support, JMX support
• Support for a comprehensive testing strategy for application developers

Inversion of Control (IoC)

• The Hollywood Principle, “Don’t call us, we’ll call you.” IoC can be thought of in terms of what distinguishes a framework from library.
• A Library performs some work when called and returns to caller. Framework encapsulates some abstract design incorporated with behavior but to use you must incorporate you unique behavior via call backs or sub-classing.
• IoC is a principle that is used to wire an application together,how dependencies or object graphs are created

To use Spring Dependency

Injection all you need is…

1. POJO with correct constructor (or setter)
2. Spring bean defined in spring-config.xml
3. Access the Bean through the Spring context bean factory

POJOs

• Constructor
• Setter

Declarative Dependency Injection with Spring Beans

• Constructor Injection
• Setter Injection
• Lookup Method Injection

Bean Factory Lookup

SomeClass instance = (SomeClass) context.getBean(“beanName”);

Where context is an implementation of

org.springframework.beans.factory.BeanFactory

Spring Bean Lookup Factory

The Factory Pattern: one object is responsible for creating and maintaining the lifecycle of another object. The lifecycle of Spring Beans (singleton) is controlled by the Bean Factory.

Spring AOP

Aspect-Oriented Programming (AOP) complements OOP by providing another way of thinking about program structure. While OO decomposes applications into a hierarchy of objects, AOP decomposes programs into aspects or concerns. This enables modularization of concerns such as transaction management that would otherwise cut across multiple objects. (Such concerns are often termed crosscutting concerns.)

How does Spring enable and make use of AOP

To provide declarative enterprise services, especially as a replacement for EJB declarative services. The most important such service is declarative transaction management, which builds on spring’s transaction abstraction. To allow users to implement custom aspects, complementing their use of OOP with AOP.