• Core Container
  • The Core module provides the fundamental parts of the framework, including the IoC and Dependency Injection features.
  • The Bean module provides BeanFactory, 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 ApplicationContext 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.
• 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.
• 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.

IoC (Inversion of Control) Container

• The Spring container is at the core of the Spring Framework.
• The container will create the objects, wire them together, configure them, and manage their complete life cycle from creation till destruction.
• The objects controlled by IoC container are called beans
• Container or framework control the objects or some portion of the program
• Two types of containers in Spring:
  • Spring BeanFactory Container
    • This is the simplest container providing the basic support for DI and is defined by the org.springframework.beans.factory.BeanFactory interface.
  • Spring ApplicationContext Container
    • This container adds more enterprise-specific functionality such as the ability to resolve textual messages from a properties file and the ability to publish application events to interested event listeners.
  • The ApplicationContext container includes all functionality of the BeanFactorycontainer, so it is generally recommended over BeanFactory. BeanFactory can still be used for lightweight applications like mobile devices or applet-based applications where data volume and speed is significant.
• Container Overview
  • org.springframework.context.ApplicationContext interface represents the Spring IoC container and is responsible for instantiating, configuring, and assembling the beans.
  • The container gets its instructions on what objects to instantiate, configure, and assemble by reading configuration metadata which is represented in XML, Java Annotations, or Java code

Dependency Injection

• What is dependency: java class (A.java) may depend on one or more other java classes. These other java classes are known as dependencies of the java class A.
• Ways to achieve DI:
  • constructor based
  • setter method based

Bean

• The objects that form the backbone of your application and that are managed by the Spring IoC container are called beans.
• These beans are created with the configuration metadata that you supply to the container.

Annotations

• @Autowired
  • applied on fields, setter methods, and constructors