Spring Framework Introduction:

 Spring framework is a dependency injection framework to make a java application loosely coupled

Inversion Of Control (IOC) and Dependency Injection(DI):

These are the design patterns that are used to remove dependency from the programming code. They make the code easier to test and maintain. Let's understand this with the following code:

1. class MangoShake{  
2. Mango mango;  
3. MangoShake(){  
4. mango=new Mango();  
5. }  
6. }  

In such case, there is dependency between the MangoShake and Mango(tight coupling). In the Inversion of Control scenario, we do this something like this:

1. class MangoShake{  
2. Mango mango;  
3. MangoShake(Mango mango){  
4. this.mango=mango;  
5. }  
6. }

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 file or annotation.

Advantage of Dependency Injection:

• makes the code loosely coupled so easy to maintain
• makes the code easy to test

Advantages of Spring Framework:

There are many advantages of Spring Framework. They are as follows:

1) Predefined Templates

Spring framework provides templates for JDBC, Hibernate, JPA etc. technologies. So there is no need to write too much code. It hides the basic steps of these technologies.

Let's take the example of JdbcTemplate, you don't need to write the code for exception handling, creating connection, creating statement, committing transaction, closing connection etc. You need to write the code of executing query only. Thus, it save a lot of JDBC code.

2) Loose Coupling

The Spring applications are loosely coupled because of dependency injection.

3) Easy to test

The Dependency Injection makes easier to test the application. The EJB or Struts application require server to run the application but Spring framework doesn't require server.

4) Lightweight

Spring framework is lightweight because of its POJO implementation. The Spring Framework doesn't force the programmer to inherit any class or implement any interface. That is why it is said non-invasive.

5) Fast Development

The Dependency Injection feature of Spring Framework and it support to various frameworks makes the easy development of JavaEE application.

6) Powerful abstraction

It provides powerful abstraction to JavaEE specifications such as JMS, JDBC, JPA and JTA.

7) Declarative support

It provides declarative support for caching, validation, transactions and formatting.