Spring Framework
Introduction to Spring framework
- The Spring Framework is a lightweight solution and a potential one-stop-shop for building your enterprise-ready applications.
- Spring is modular, allowing you to use only those parts that you need, without having to bring in the rest.
- Example
- you can use the IoC container, with any web framework on top,
- you can also use only the Hibernate integration code or the JDBC abstraction layer.
- The Spring Framework supports declarative transaction management, remote access to your logic through RMI or web services, and various options for persisting your data.
- It offers a full-featured MVC framework, and enables you to integrate AOP transparently into your software.
- Spring is designed to be non-intrusive, meaning that your domain logic code generally has no dependencies on the framework itself. In your integration layer (such as the data access layer), some dependencies on the data access technology and the Spring libraries will exist. However, it should be easy to isolate these dependencies from the rest of your code base.
Spring framework provides comprehensive infrastructure support so that application developer can focus on application.
Examples of how you, as an application developer, can benefit from the Spring platform:
- Make a Java method execute in a database transaction without having to deal with transaction APIs.
- Make a local Java method an HTTP endpoint without having to deal with the Servlet API.
- Make a local Java method a message handler without having to deal with the JMS API.
- Make a local Java method a management operation without having to deal with the JMX API.
Spring Framework Architecture/Modules
- Spring framework is a layered architecture which consists of several modules.
- All modules are built on top of Core Container/Module and depends on it for functioning.
- Each module provides specific set of features that helps developer to build enterprise app.
- Each module is independent of other except core module.
- Below is the Spring framework architecture
Core Container
The Core Container consists of the spring-core
, spring-beans
, spring-context
, spring-context-support
, and spring-expression
(Spring Expression Language) modules.
The spring-core
and spring-beans
modules provide the fundamental parts of the framework, including the IoC and Dependency Injection features. The BeanFactory
is a sophisticated implementation of the factory pattern. It removes the need for programmatic singletons and allows you to decouple the configuration and specification of dependencies from your actual program logic.
The spring-context
module builds on the solid base provided by the Core and Beans modules: it is a means to access objects in a framework-style manner that is similar to a JNDI registry. The Context module inherits its features from the Beans module and adds support for internationalization (using, for example, resource bundles), event propagation, resource loading, and the transparent creation of contexts by, for example, a Servlet container. The Context module also supports Java EE features such as EJB, JMX, and basic remoting. The ApplicationContext
interface is the focal point of the Context module. spring-context-support
provides support for integrating common third-party libraries into a Spring application context for caching (EhCache, Guava, JCache), mailing (JavaMail), scheduling (CommonJ, Quartz) and template engines (FreeMarker, JasperReports, Velocity).
The spring-expression
module provides a powerful Expression Language for querying and manipulating an object graph at runtime. It is an extension of the unified expression language (unified EL) as specified in the JSP 2.1 specification. The language supports setting and getting property values, property assignment, method invocation, accessing the content of arrays, collections and indexers, logical and arithmetic operators, named variables, and retrieval of objects by name from Spring’s IoC container. It also supports list projection and selection as well as common list aggregations.
Data Access/Integration
The Data Access/Integration layer consists of the JDBC, ORM, OXM, JMS, and Transaction modules.
The spring-jdbc
module provides a JDBC-abstraction layer that removes the need to do tedious JDBC coding and parsing of database-vendor specific error codes.
The spring-tx
module supports programmatic and declarative transaction management for classes that implement special interfaces and for all your POJOs (Plain Old Java Objects).
The spring-orm
module provides integration layers for popular object-relational mapping APIs, including JPA, JDO, and Hibernate. Using the spring-orm
module you can use all of these O/R-mapping frameworks in combination with all of the other features Spring offers, such as the simple declarative transaction management feature mentioned previously.
The spring-oxm
module provides an abstraction layer that supports Object/XML mapping implementations such as JAXB, Castor, XMLBeans, JiBX and XStream.
The spring-jms
module (Java Messaging Service) contains features for producing and consuming messages. Since Spring Framework 4.1, it provides integration with the spring-messaging
module.
Web
The Web layer consists of the spring-web
, spring-webmvc
, spring-websocket
, and spring-webmvc-portlet
modules.
The spring-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. It also contains an HTTP client and the web-related parts of Spring’s remoting support.
The spring-webmvc
module (also known as the Web-Servlet module) contains Spring’s model-view-controller (MVC) and REST Web Services implementation for web applications. Spring’s MVC framework provides a clean separation between domain model code and web forms and integrates with all of the other features of the Spring Framework.
The spring-webmvc-portlet
module (also known as the Web-Portlet module) provides the MVC implementation to be used in a Portlet environment and mirrors the functionality of the Servlet-based spring-webmvc
module.
Messaging
Spring Framework 4 includes a spring-messaging
module with key abstractions from the Spring Integration project such as Message
, MessageChannel
, MessageHandler
, and others to serve as a foundation for messaging-based applications. The module also includes a set of annotations for mapping messages to methods, similar to the Spring MVC annotation based programming model.
AOP and Instrumentation
The spring-aop
module provides an AOP Alliance-compliant aspect-oriented programming implementation allowing you to define, for example, method interceptors and pointcuts to cleanly decouple code that implements functionality that should be separated. Using source-level metadata functionality, you can also incorporate behavioral information into your code, in a manner similar to that of .NET attributes.
The separate spring-aspects
module provides integration with AspectJ.
The spring-instrument
module provides class instrumentation support and classloader implementations to be used in certain application servers. The spring-instrument-tomcat
module contains Spring’s instrumentation agent for Tomcat.
Test
The spring-test
module supports the unit testing and integration testing of Spring components with JUnit or TestNG. It provides consistent loading of SpringApplicationContext
s and caching of those contexts. It also provides mock objects that you can use to test your code in isolation.