What is Spring?
Spring is a Lightweight Application Framework
Where Struts, WebWork and others can be considered Web frameworks, Spring addresses all tiers of an application.
Adv of Spring
Spring proposes a new paradigm, a pluggable, non- intrusive and robust framework
Unlike other frameworks and APIs, spring does not impose itself wholly on to the design of a project. Spring is modular and has been divided logically into independent packages, which can function independently. The architects of an application have the flexibility to implement just a few spring packages and leave out most of the packages in spring. The Spring Framework would not feel bad with this attitude and on the contrary encourages users to introduce Spring into existing applications in a phased manner. So no matter what kind of framework you are using now Spring will co-exist with it without causing you nightmares and further more Spring will allow you to choose specific packages in Spring.
It also provides integration modules for major O/R mapping tools like Hibernate and JDO. Spring provides all these in a modular fashion without imposing any layer on to the user.
Spring also provides transaction management support using Java classes, email support packages using framework classes, web services support through proxies and many more features.
As mentioned earlier all these packages are optional and spring does not make any of them mandatory.
Spring is based on the Inversion of Control/Dependency Injection pattern.
Benefits of the Spring Web MVC Framework
The Spring Web MVC Framework is a robust, flexible, and well-designed framework for
rapidly developing web applications using the MVC design pattern.The benefits
achieved from using this Spring module are similar to those you get from the rest of the
Spring Framework. Let's review a few of these.
Easier testing--This is a common theme you will find across all the Spring classes.
The fact that most of Springs classes are designed as JavaBeans enables you to
inject test data using the setter methods of these classes. Spring also provides mock
classes to simulate Java HTTP objects (HttpServletRequest, for example), which
makes unit testing of the web layer much simpler.
Bind directly to business objects --Spring MVC does not require your business
(model) classes to extend any special classes; this enables you to reuse your business
objects by binding them directly to the HTML forms fields. In fact, your
controller classes are the only ones that are required to extend Spring classes (or
implement a Spring controller interface).
Clear separation of roles--Spring MVC nicely separates the roles played by the
various components that make up this web framework. For example, when we discuss
concepts such as controllers, command objects, and validators, you will begin
to see how each component plays a distinct role.
Adaptable controllers--If your application does not require an HTML form, you
can write a simpler version of a Spring controller that does need all the extra
components required for form controllers. In fact, Spring provides several types of
controllers, each serving a different purpose. For example, there are no-form controllers,
simple form controllers, wizardlike form controllers, views with no controllers,
and even prepackaged controllers that enable you to write views without
your own custom controller.
Simple but powerful tag library--Springs tag library is small, straightforward, but
powerful. For example, Spring uses the JSP expression language (EL) for arguments
to the <spring:bind> tag.
Web Flow--This module is a subproject and is not bundled with the Spring core
distribution. It is built on top of Spring MVC and adds the capability to easily
write wizardlike web applications that span across several HTTP requests (an
online shopping cart, for example).
View technologies and web frameworks--Although we are using JSP as our view
technology, Spring supports other view technologies as well, such as Apache
Velocity (jakarta.apache.org/velocity/) and FreeMarker (freemarker.org).This is a
powerful concept because switching from JSP to Velocity is a matter of configuration.
Furthermore, Spring provides integration support for Apache Struts (struts.
apache.org), Apache Tapestry (jakarta.apache.org/tapestry), and OpenSymphony's
WebWork (opensymphony.com/webwork/).
Lighter-weight environment--Spring enables you to build enterprise-ready applications
using POJOs; the environment setup can be simpler and less expensive because you
could develop and deploy your application using a lighter-weight servlet container.
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