Spring Core Module

Spring Core Module

Spring core is base module for spring framework.

All the other modules in the spring are developed on the top of core module. 

In simple words Spring core module is providing fundamental concepts of spring, they are IOC and DI to achieve loosely coupling between Java classes.

Java Application can have multiple classes (service, controller, model, etc..!) and its methods, as part of application execution one class method should talk to another class. 

How one Java class can talk to another Java class?

By inheriting the properties

By creating objects

 

Java Code

If we use above approach then our classes will be tightly coupled,

because we are creating objects for kotak, axis bank and then calling that class methods from main class(Bank).

Suppose If we change methods of kotak class method, we have to do changes in main class(Bank) too.

Spring framework is used IOC container, Dependency Injection concepts to achieve loosely coupling between Java classes.

IOC container

Dependency Injection.

 

 

IOC Container

IOC container creates an object, destroying object and manage their complete lifecycle of Spring bean (Java class).

The container gets an Instruction what object to instantiate, configuration and assemble by reading configuration metadata.

This metadata can be xml file, annotation file or Java-based configuration.

 

We can start IOC container in 2 ways.

1)     BeanFactory

2)     ApplicatioContext

 

loading xml file from classpath

Resource resource = new ClassPathResource("Beans.xml");

 

We can load file from external file location also

Resource resource = new FileSystemResource("D://files/Beans.xml");

 

1) IOC container started with lazy loading mechanism

    BeanFactory fatory = new XmlBeanFactory(resource);

 

2) IOC container started with eager loading mechanism

    ApplicationContext factory=new ClassPathXmlApplicationContext("Beans.xml");

 

ApplicationContext factory directly loading xml file.

 

Note: XmlBeanFactory got deprecated in spring framework, so it is not recommended to use.

                                                  

All XmlBeanFactory Functionalities supported by ApplicationContext factory and also provides additionals features also.

 

ApplicationContext factory features are 

1) Annotation Based Configuration Support

2) I18N Applications Support

3) Event Handling Support            

 

 

Dependency Injection 

Injecting dependent class object into target class object is called as dependency Injection.

We can perform Dependency Injection in 3ways. 

1) Setter Injection

2) Constructor Injection

3) Field Injection

 

Injecting dependent class object into target class object using

target class setter method then it is called as "Setter Injection".

 

Injecting dependent class object into target class object using

target class constructor then it is called as "Constructor Injection".

 

Injecting dependent class object into target class object using

target class field then it is called as "Field Injection".