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Spring

  • it is an open source framework for building enterprise Java apps
  • it aims to simplify the complex and cumbersome enterprise Java app development process by offering a framework that includes technologies such as
    • Aspect-oriented programming (AOP)
    • Dependency Injection (DI)
    • Plain Old Java Object (POJO)
  • it is a lightweight framework that can be used to create scalable, secure, and robust enterprise web apps
  • it can be considered as a collection of sub frameworks such as
    • Spring Web Flow
    • Spring MVC
    • Spring ORM
  • Spring also supports Kotlin and Groovy
  • it is also the base that powers all other spring based projects such as
    • Spring Boot
    • Spring Cloud
    • Spring GraphQL

Core Features​

Inversion of Control (IoC) Container​

  • it is one of the core features of Spring that provides a streamlined way to configure and manage Java objects
  • it is responsible for managing the lifecycle of a defined Java object, significantly increasing the configurability of a Spring-based application
  • it uses the dependency injection or dependency lookup patterns to provide the object reference during runtime
  • it consists of assembler code that is required for configuration management
  • Spring provides org.springframework.beans and org.springframework.context packages that can be used to facilitate these functions

Support for aspect oriented programming​

  • AOP aims to provide more modularity to the cross-cutting concerns, which are functions that span across the application, such as
    • Logging
    • Caching
    • Transaction management
    • Authentication
  • AOP complements object-oriented programming by providing a different way to structure the program, where OOP modularity is based on classes
  • In AOP, the main unit of modularity is an aspect (cross-cutting concern)
    • This enables users to use AOP to create custom aspects and declarative enterprise services
    • The IoC container does not depend on AOP, offering further freedom for developers to select their preferred programming method
  • However, Aspect-Oriented Programming combined with the Spring IoC provides a robust middleware solution

Data access framework​

  • Database communication issues are one of the common issues developers face when developing applications
  • Spring simplifies the database communication process by providing direct support for popular data access frameworks in Java, such as
    • JDBC, Hibernate, Java Persistence API (JPA)
  • it offers features such as resource management, exception handling, and resource wrapping for all the supported data access frameworks, further simplifying the development process

Transaction management framework​

  • Unlike the Java Transaction API (JTA), the Spring Transaction Management Framework is not limited to global and nested transactions
  • Spring offers an abstraction mechanism for Java that enables users to:
    • Work with local, global, and nested transactions
    • Save points
    • Simplify transaction management across the application
  • The Spring Data Access Framework directly integrates with the Transaction Management Framework with support for messaging and caching
    • This enables developers to create feature-rich transactional systems that span across the applications without depending on EJB or JTA

Spring MVC framework​

  • The Spring MVC enables developers to create applications using the popular MVC pattern
  • It is a request-based framework that allows developers to easily create customized MVC implementations that exactly suit their needs
  • The core component of Spring MVC is the DispatcherServlet class which handles user requests and then forwards them to the correct controller
    • This allows the controller to process the request, create the model and then provide the information to the end-user via a specified view

Spring web service​

  • This Spring Web Service component provides a streamlined way to create and manage web service endpoints in the application
  • It offers a layered approach that can be managed using XML and can be used to provide mapping for web requests to a specific object

Spring test frameworks​

  • Spring simplifies testing within the framework with components like
    • Mock objects
    • TestContext framework
    • Spring MVC Test

Spring Framework Architecture​

  • Spring is built using different modules that enable different functionality

Spring Architecture

Core container​

  • This contains the fundamental modules that are the cornerstone of the Spring framework
    • Core (spring-core) is the core of the framework that power features such as Inversion of Control and dependency injection
    • Beans (spring-beans) provides Beanfactory, which is a sophisticated implementation of the factory pattern
    • Context (spring-context) builds on Core and Beans and provides a medium to access defined objects
      • ApplicationContext interface is the core part of the Context module, and the spring-context-support provides support for third-party interactions such as caching, mailing, and template engines
    • SpEL (spring-expression) enables users to use the Spring Expression Language to query and manipulate the object graph at runtime

Data access/integration​

  • This includes the modules that are used to handle data access and transaction processing in an application
    • JDBC (spring-jdbc) provides a JDBC abstraction layer that eliminates the need to separate JDBC coding when dealing with databases
    • ORM (spring-orm) are integration layers for popular object-relational mapping API such as JPA, JDO Hibernate
    • OXM (spring-oxm) is the abstraction layer that supports Object/XML mapping implementations like JAXB, XStream
    • JMS (spring-jms) is the Java Messaging Service module that creates and consumes messages that directly integrate with the Spring messaging module
    • Transaction (spring-tx) offers programmatic and declarative transaction management for classes that include special interfaces and POJOs

Web​

  • The Web layer relates to modules that power web-based functions in Spring
    • WebSocket (spring-websocket) powers the web socket-based communication for clients and servers
    • Servlet (spring-webmvc) is the Spring WebMVC module that contains the MVC and REST implementations
    • Web (spring-web) provides all the basic web-oriented features and contains an HTTP client and web-related parts of the Spring remoting
    • Portlet (spring-webmvc-portlet) provides the MVC implementation to be used in a portlet environment

Other Modules​

  • AOP (spring-aop) provides an aspect-oriented programming implementation that can be used when creating applications
  • Aspects (spring-aspects) enables direct integration with the AspectJ programming extension by the eclipse foundation
  • Instrumentation (spring-instrument) is the class instrumentation support and class loader implementations for application servers
  • Messaging (spring-messaging) provides a robust platform to manage messaging in applications
  • Test (spring-test) is the Spring test module that supports unit and integration testing with JUnit and TestNG