Spring
Spring
was developed by "Rod Jonson"
in 2003. Spring framework makes the easy development of JEE
application. Spring
is a lightweight framework. It can be thought of as a framework of frameworks because it provides support to various frameworks. Like,
Struts, EJB, JSF, GWT...
The
spring framework comprises several modules such as IOC, AOP, DAO,
Context, ORM, Web MVC etc.
Advantages
of Spring Framework:
There
are many advantages of Spring framework.
Predefined Templates:
Spring
framework provides templates for JDBC, Hibernate, JPA etc. So, there
is no need to write too much code. It hides the basic steps of these
technologies.
Let's
take the example of JDBC template you no need to write the code
exception handling, creating connection, creating statement,
committing transaction, closing connection etc. You need to write the
code for executing query. Thus it saves lot of JDBC code.
Loose
Coupling:
The
Spring applications are loosely coupled because of dependency
injection.
Easy
to test:
The
dependency injection makes easier to test the application. The EJB or
Struts applications are required server to run applications. But,
Spring framework does not require server.
Lightweight:
Spring
framework is lightweight because of POJO implementation. The spring framework doesn't force the programmer to inherit any class or
implement any interface. That is why this is said non-invasive.
Fast
Development:
The Dependency injection of Spring framework and it support various
framework makes the easy development of JEE applications.
Powerful
abstraction:
It
provides powerful abstraction to JEE specification such as JMS, JDBC,
JPA and JTA.
Declarative
Support:
It
provides declarative support for catching , validation and formatting.
Spring
Framework:
Test:
Test
layer provides support of testing with JUnit and TestNG.
Spring
Core Container:
Spring
core container contains core, beans, context and expression language
modules.
Core
& Beans:
These
modules provides Inversion Of Control (IOC) and Dependency Injection (DI) features.
Context:
This
module supports Internationalization (i18n) , EJB , JMS , Basic Remoting.
Expression
Language(EL):
It
is an extension to the EL defined in JSP. It provides support to
setting and getting property values, method invocation, accessing
collections and indexers, named variables, logical & arithmetic operations, retrieval of objects by name, etc.
AOP,
Aspects & Instrumentation:
These
modules supports Aspects Oriented programming implementation where you
can use Advice's, point-cut's etc to decouple the code. The
Aspects module provides support to integration with AspectJ.
The
Instrumentation module provides support to class instrumentation and
class loader implementation.
Data
Access / Integration:
This
group comprises of JDBC, ORM, OXM, JMS and transaction modules. These
modules basically provides support to interact with the database.
WEB:
This
group comprises of web, web-serlvet, web-struts and web-portlet.
These modules support to create web application.
Inversion Of Control (IOC) & Dependency Injection (DI):
Above design patterns are used to remove dependency from the
programming code. They make the code easier to test and maintain,
class Student { Address address; Student(){ address = new Address(); } }
In such case there is dependency in between Student and Address (tightly coupling). In the inversion of control scenario.
class Student{ Address address; Student(Address address){ this.address = address; } } |
Thus, IOC makes the code loosely coupled, in such case, there is no need to modify the code if our logic is moved to new environment.
In
Spring framework, IOC container is responsible to inject the
dependency. We provide metadata to the IOC container either by XML
files or annotation.
Advantages
of Dependency Injection:
- makes the code loosely coupled so easy to maintain.
- makes the code easy to test.
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