If you have been using Spring Framework for sometime , you will be aware that the Spring Framework has undergone several major changes in the latest Spring version 3.x. Spring Framework is now based on Java 5 and Java 6 fully supported. It has incorporated all the important features of Java latest versions. Spring version 3.0 encourages the developers to use Java Annotations instead of the configuration xml. This post will talk on the Annotation based Dependency Injection mechanism using Spring 3.0.

Spring framework has a full-fledge support for the Database Access Objects(DAO). Spring’s support of DAO is not limited with the relational database like MySQL , Oracle , etc . It has support for Object Relational Databases like , HSQL , JDO etc. Whan I talk about suppot it means a lot of things.

Before going into the details , let us ask a question to ourselves .What is the real problem in coding a JDBC without a framework support ?

Spring is a very good modular framework. Each module of the framework can be used depending on the various need in an application. Lets take an example of a J2EE-based web application which can use Spring-DAO module for it’s data base layer or Spring-MVC to make the navigation between Model-View-Controller more modular and testable.
But , there might be a situation where Spring-MVC is not your need , rather you would like to take advantage of Spring-DAO module along with normal servlets and jsps. What to do then ?

I have discussed on the concept of Dependency Injection in my last post . This post is about a specific type of Dependency Injection adopted by Spring. It is called Setter Injection. In Java POJO(Plain old java object) world , setters and getters are very common terms. A setter which sets an attribute value of a class. A getter which return the attribute value of a class.

Java classes and objects should be as much as possible loosely coupled with other java classes and objects. The loosely-coupled behavior allows a Java code to be re-usable ,test-worthy , modular and well maintained. Often , A class depends on another class and arise the coupling .

Dependency Injection(DI) mechanism helps to introduce the loose coupling which makes your code more modular and testable.

The container which supports this dependency injection concept is called the IOC (Inversion of control) Container. Spring uses the concept of IOC and dependency injection to locate and inject services for you.

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