Spring Framework concepts

Spring Framework concepts 
Spring framework is a light weight component for creating a java ee applications.Spring framework  is an abstraction layer on top of the existing technologies. A spring framework will provide common functionalities for the projects as ready made,and the developer will build the remaining code for the projects.

In this Spring framework have mainly 3 injunctions are there.There are
  1.setter injection
  2.construction injection
  3.interface injection

Setter Injection: In a spring framework if the dependencies  are injected by calling the setter method of an object at run time  then is called a setter injection.
Constructor Injection: if the dependencies are injected by calling the constructor of an object at run time then it is called constructor injection.
Interface Injection: if the dependencies are injected by the calling a method provided by a interface  then it is calling interface injection.

Spring framework supports all the three types of dependency injections.The interface injection is supported only at particular time,that is in a bean life cycle process.

setter injection example:
   
 public class TravelService
 {
     private Vehicle vehicle
     {
     public void setVehicle(Vehicle vehicle)
      {
          this.vehicle=vehicle;
       }
    }

constructor injection example:
   
 public class TravelService
 {
     private Vehicle vehicle
     {
     public  TravelService(Vehicle vehicle)
      {
          this.vehicle=vehicle;
       }
    }

interface injection example:
   
 public class Demo implements BeanFactoryAware
 {
     private BeanFactory fact;
     {
     public void set BeanFactory(Beanfactory fact)
      {
          this.fact=fact;
       }
    }
-->here interface provided  method is used for injecting the dependency.So it is a interface injection.

Spring Bean: Spring bean is a pojo class. And a spring bean may or may not contain the default constructor.
The difference between the spring bean and the java bean is java bean may contain a default constructor,in spring bean mayor may not contain the default constructor.

To create a spring application required files are
-->Bean class
-->web.xml
-->client class


Steps for creating a spring bean object in a client application:

step-1: create a resource object
        Resource r=new ClassPathResource("beans.xml");
step-2: create spring container object
            BeanFactory factory=new XmlBeanFactory(r);
step-3: get the bean object from the container by using id  with calling getBean()method
            Object o=factory.getBean("id");
step-4:Type cast the Object class to our spring bean object.the it calls our business method.
          DemoBean db=new DemoBean();
            db.showMessage();