Spring Book – Chapter 1 – Introduction

CHAPTER 1
INTRODUCTION
Over the last few years, Spring has grown substantially, surpassing many other
frameworks. Spring enables you to concentrate on writing less Spring-Framework-related
code and more application code, which is vital in the fast-changing and cost-sensitive world
of enterprise applications. Since its initial release in 2004, Spring has reinvented itself
multiple times and become prominent in the industry as a strong force in the framework
market. This has not only made the Spring Framework renowned, but it has also put healthy
pressure or rather competition on well-known industry specifications (Java EE) and the
application-server market. In the Java world, this is a very exciting time and a very important
turning point.
In this chapter, I introduce Spring Framework as a whole (If I could, I would compel you to
use it). Before explaining the nitty-gritty, I give you reasons to choose Spring for your
application. Then I explain the Spring framework architecture and its features and, more
important, introduce you to the main modules on which Spring Framework is based.
The complete book is available as a blog entry in www.javacodebook.com.
Why Spring?
Spring provides an extensive, portable, open source-application-development framework for
Enterprise Java. Starting with Spring, you can build whatever you want: reservations system,
banking systems, social networks, and more. Spring expands to meet your needs; you can
integrate various security models, databases, web services, mobile clients, messaging
systems, and so on that are required in today’s agile enterprise applications. Another key
advantage is that Spring fits directly into your current infrastructure, because Spring uses the
same Plain Old Java Objects (POJOs) you use every day. Once you start creating

applications with Spring, you can deploy it everywhere in the certainty that it will thrive and
adapt to the environment with ease.
If you need your application to be better, newer, and speedier, Spring is the right alternative
for development. Surveys suggest that more and more Java developers around the world
are moving toward Spring. For instance, recent analysis from Evans Data ("Spring Usage
Study," Evans Data Corporation, September 2011) analyzes the ubiquity achieved by Spring
as summarized below:
• Spring is the framework of choice among knowledgeable Java developers.
• Spring developers report productivity and speed of deployment as the top reasons for
using it: 70 percent of Spring users report at least a 50 percent productivity gain by
using it, and 73 percent report that the framework allows them to deliver projects
twice as fast.
• It is estimated that more than two thirds of Java developers today are either using
Spring or plan to do so within the next two years.
• More than half of all existing Spring users expect to considerably increase their use
of this framework over the next few years.
• Spring users are more cloud ready and it is considered that heavy Spring adopters
are more likely to have already deployed their applications to the cloud.
• More than half of all existing Spring developers report that they plan to move their
Java applications to a lightweight server, such as Apache Tomcat, within one year.
( Get more information from http://www.vmware.com/company/news/releases/vmw-
spring-momentum-3-14-12.html )
Shared feedback from developers around the world highlights the following advantages of
Spring Framework:
• Easier to understand. Not rocket science.
• If you have any issues with the framework code, you can just open the source code
and with minimal effort understand it very easily.

• Makes users highly productive, shortens development time.
• For junior developers, it’s an excellent learning tool because so many live, proven
Java pattern examples can be seen throughout the framework code.
• Enables developers to cut out tons of redundant code, reducing boilerplate code in
their applications. Programmatic catching of exceptions and cleaning up of
resources, etc., are things of the past.
• Spring’s ability to wire objects at runtime is incredible. Injection of right type-safe
objects wherever needed is transparently handled by the Spring container.
• A la carte framework—Plug-in what you want and use it.
What Is Spring Framework?
Spring Framework is built on well-defined goals and a coherent philosophy. Its main aim is to
make Java EE development easier. This section explains Spring Framework’s main goals
and its role in the development of enterprise applications.
Goal
Spring's main aim, according to Rod Johnson (see sidebar) is to make Java EE easier to
use and promote good programming practice. Even though POJO-based programming
model is practiced in many enterprise applications, Spring Framework takes this concept into
a different level by incorporating this model into it and making it applicable in a wide range of
environments available. Due to this style of programming model, the framework keeps itself
open to take advantages provided by the environment it works on without losing portability in
the process.
Rather than Spring writing its own bit of code for common functionalities like logging,
connection pools, transaction coordinators etc., it allows the developers to appropriately plug
in the various packages available as open-source projects (For example, Commons Logging

package can be used for all common logging purposes, Commons DBCP package can be
used for connection pooling etc.) into the framework with mere configuration and with ease.
By doing so it allows using the best package available in the open-source world and also
keeps it open for future change as the case may be. All of this Spring does by keeping in
mind that it doesn’t gets itself locked to any platform-specific or non-standard technology
making it one of reason to use the framework in any enterprise application development.
Spring over the period has grown into a mature framework transforming itself into a one-stop
shop capable of handling most of the infrastructural concerns which exists in a typical
modern enterprise application. Applications are there because it has to support a business
requirement. Spring provides applications with the capability of taking care of your core
business objects easily and also allows changing it with minimal impact on the application as
a whole according to changing business scenarios.
Rod Johnson is an enterprise Java architect specializing in
scalable web applications. He has worked with both Java and
JEE since their release and is also a core member of JSR
154 Expert Group entrusted with defining the Servlet 2.4
specification. He started developing frameworks for web
application in 2000 while working as independent consultant.
The Spring project was started by him in 2002, and it first
official release was in March 2004. Johnson released this
framework with the publication of his book Expert One-on-
One Java EE Design and Development (Wrox Press, 2002).
Spring Framework’s Role in Enterprise Applications
Spring Framework includes core support for:
• Application configuration
• Enterprise integration
• Data access
• Testing

• Web application-development support
• Enterprise application-development support
Application Configuration
A typical application comprises various components working together to carry out a
particular application-use case. Spring helps you build this configuration with ease. With
Spring, components constituting a use case don’t worry about one another and at any point
they can be swapped to keep up with the business change (agility).
Enterprise Integration
An enterprise application doesn’t work in isolation. It requires various enterprise services and
resources such as security, messaging, caching, transactions, etc., to constitute an end-to-
end application to meet real-life application needs. With ease and agility, Spring does this by
keeping your application code simple and both unit and integration testable. It can be easily
plugged into any standard Java EE application server and also is capable of stand-alone
usage.
Data Access
An enterprise application accesses data stored in a relational database to carry out various
business functions and to enforce various business validations. Spring makes data access
easy and effective. It supports all major data-access technologies, such as Hibernate, JPA,
JDBC, etc.; manages these resources transparently from the developer; and also offers tons
of APIs, which enables developers to concentrate more on the core business coding and
thereby increase productivity.
Testing
Unit and integration testing is essential for any enterprise application. It helps with
decompiling objects from the environment where it resides and makes it easier to test the
application in isolation from its actual deployment environment. More important, it helps in
system/integration testing to see that all the components constituting an enterprise
application work properly. This testing can be done in the actual environment as well as in

isolation from the actual environment, which is a big plus compared to other framework
platforms.
Web Application-Development Support
Spring includes a powerful and highly configurable Model-View-Controller web framework
called Spring MVC. Even though very much similar to Apache Struts, it can never be said as
derived from it. Frankly saying no copyright infringement spotted. Now to look into the
similarities, Struts Action class is similar to Spring MVC Controller class and this object is
multi-threaded in nature will a single instance being used for servicing all the clients. Spring
MVC has some significant advantages over Struts, however—it has a powerful navigation
rule framework, Spring Web Flow, which equals its powerful web framework for application
development. Even though Spring has its own implementation for a web framework, it has
kept its main goal of seamlessly integrating with other famous web frameworks, such as
Struts and Java Server Faces (JSF).
Enterprise Application-Development Support
Spring’s core strength lies in its ability to integrate with common and most required services
in enterprise applications. It has modules for creating and maintaining web services,
scheduling jobs, integrating with messaging services, and so on. This modular coding
support ensures good manageability for applications.
Spring Framework History
Spring Framework has a philosophy of “release early, release often,” because of which
maintenance releases and minor enhancements are released every four to six weeks. Major
release details with major changes introduced, are as follows, beginning with most recent
are as summarized below:
Spring 3.1 (released December 2011)

• Bean definition profiles - better classification and grouping of beans using the
concept of profiles, both using annotation (@Profile) and XML is a huge addition in
the Spring Framework. Combining with the concept of "Environment", it provides
ease of use of profiles.
• Cache abstraction using declarative configuration - adds support for transparently
adding caching behavior by allowing consistent uses of various caching solutions
available in the market to existing Spring applications.
• Servlet 3.0-based WebApplicationInitializer - WebApplicationInitializer is an alternate
to the traditional web application descriptor file web.xml.
• JPA package scanning without persistence.xml and with support for Hibernate 4.0 -
This version supports Hibernate 4.0.
• First class Java 7 support - Supports Java 7 in all aspects.
Spring 3.0 (released December 2009)
• Spring Expression Language - introduction of new expression language similar to
Unified EL syntactically but offering advanced and other significant features.
• Inversion of Control enhancements/Java-based bean metadata - The key features in
Spring JavaConfig project has been migrated to the core Spring Framework.
• General-purpose-type conversion system and field-formatting system - the package
org.springframework.core.convert provides classes which provides general type
conversion system which defines SPI to implement conversion logic.
• Object-to-XML mapping functionality (OXM) moved from Spring Web Services
project to the core Spring Framework.
• Comprehensive REST support - support for REST based services in the server and
client side.

• @MVC additions - Introduction of "mvc" namespace simplifies MVC related
configurations in the Spring configuration file. Addition of other annotations makes
the annotation based MVC application coding easy, simple and less of configuration.
• Declarative model validation - JSR-303 validation support using Hibernate validation
as default provider. There are other validation enhancements also included as part of
this release of Spring Framework.
• Early support for Java EE 6 - Core API's updated to Java 5 utilizing its features as
well as early support for Java EE 6.
• Embedded database support - support for embedded databases like HSQL, H2 and
Derby in a native fashion. It also hosts extendable API which can be used to plug in
to newer emerging databases.
Spring 2.5 (released November 2007)
• Full support for Java 6 and Java EE 5 which includes JDBC 4.0, JTA 1.1, JavaMail
1.4, JAX-WS 2.0 etc.
• Full-featured, annotation-driven dependency injection, such as @Autowired,
@Controller, etc., including support for “qualifiers”.
• Auto-detection and Auto-configuration of various application components available in
the classpath into the Spring's IoC container.
• Introduction of new XML configuration namespaces namely "context" and "jms" for
more convenience.
• Capability of packaging Spring Framework jars as OSGI-compliant bundles.
Spring 2.0 (released October 2006)
• Easier XML configuration - new XML configuration syntax based on XML Schema
along with new and updated DTD.

• New bean scopes - in addition to existing two bean scopes, it adds new additional
scopes which can be used according to the environment in which the Spring
Framework is deployed. It also adds the capability of writing your own custom bean
scopes.
• Easier AOP XML configuration - support for AspectJ along with simplification in AOP
configurations in the form of namespace and new annotations.
• Portlet Framework - ships with new Portlet Framework very much similar to the
Spring MVC Framework.
• Dynamic language support - support for beans written in other languages. At the
moment Spring Framework supports JRuby, Groovy and BeanShell languages.
Spring 1.2 (released May 2005)
• Spring 1.2.6 Framework wins a Jolt productivity award and JAX innovation award.
Spring 1.1 (released September 2004)
• Support for JMS message sending and receiving.
• Using Spring's consistent data-access abstraction, support for Apache OJB as an
ORM alternative introduced.
• Significantly improved JDO support.
• Automatic translation of SQL related exceptions (SQLException) and other JDBC
related exceptions.
• When working with JDBC, support for declarative transaction management capable
of handling nested transactions and savepoints.
• Enhanced support for Apache Velocity and Freemarker.

Spring 1.0 (released March 2004)
• AOP-interception-framework based.
• Declarative and programmatic transaction management support with plugging in
capability which can be used very easily to switch between the two.
• Generic DAO support, providing a generic data-access exception hierarchy for use
with any data-access strategy.
• Abstraction of JDBC related services with good support for BLOB/CLOB operation
which are conceived more difficult to work on.
• Hibernate support, providing SessionFactory management and transaction-scoped
ThreadLocal Sessions.
• Mailing abstraction with full support for JavaMail with advanced support for working
with files which needs to be attached along with the mail.
• Scheduling abstraction and support for well know scheduling frameworks like Quartz
and JDK's Timer which can be used for invoking methods in the Spring-managed
beans.
• Remoting abstraction and support for RMI, JAX-RPC and Caucho's Hessian/Burlap
which can be made use for exposing Spring-managed beans.
Note: Only important and notable features in each release is
covered in this section of the Chapter as packing too much
content would not be an ideal start for this 'beginning' style
Spring book.
Spring Framework Architecture

Spring as always tries to bring in good practices in the industry and also embraces proved
best practices with both hands. It gives developers a consistent way of managing the all-
important business objects and also encourages to program your logic in interfaces rather
than classes. Spring Framework is based on its own well-known (Inversion of Control) IoC
container which uses JavaBean and it's properties. This IoC container is the main building
block of Spring and is used in all the architectural tiers in a typical enterprise application.

Spring Book – Chapter 1 – Introduction

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Spring Book – Chapter 1 – Introduction