Spring Notes

Spring uses Factory Pattern - as the creation of objects is done through Bean Factory

Setter Injection - using property tag
Constructor Injection - using constructor-arg -- we use type and index to solve ambiguity

Inner Beans - A bean defined within another bean for a property
Aliases - alternate bean name - can be specified using <alias> tag and also using the name attribute of <bean>
idref - validating to ensure the bean referenced using only the id attribute

we can use autowire = "byName/byType/constructor"

Bean Scopes
1. Singleton - default, can have only instance at any point of time for a given spring container
2. Prototype - each call will a separate bean
The below are used in web-context
3. request - each request will have a new bean
4. session - the bean will be reused within the session
5. global session - used in the context of portlets


ApplicationContextAware - need to override setApplicationContext()
BeanNameAware - need to override setBeanName()

Bean Definition Inheritance
--> One bean can use re-use the other bean's properties - we have to use 'parent' attribute

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Life Cycle Methods
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--> use ctx.registerShutdownHook() to close/destroy all the beans tht hv been configured
InitializingBean - need to implement afterPropertiesSet() - will execute once bean has finished initialisation
DisposableBean - need to implement destroy() - will execute before destroying the bean
-----------------------Alternative --------------------------
write custom methods initCustom() and destroyCustom()
In the spring config, declare in the bean definition as follows:
init-method="initCustom"
destroy-method ="destroyCustom"
------------------Alternative - we can define globally for all beans ----------------
In the spring config, declare in the root <beans> tag
default-init-method="initCustom"
default-destroy-method ="destroyCustom"

BeanPostProcessor
-> Executes after every bean is initialised
--> Need to implement the below callback methods:
 postProcessBeforeInitialization(Object bean, String nameOfTheBean)
 postProcessAfterInitialization(Object bean, String nameOfTheBean)
--> Need to declare the bean which implements BeanPostProcessor in the config file

BeanFactoryPostProcessor
--> Executes when the beanFactory is initialized, then only the singleton's for the beans are initialized
--> Need to implement the postProcessBeanFactory(ConfigurableListBeanFactory beanFactory)
-->Ex:- provided by spring out-of-the box PropertyPlaceHolderConfigurer
   <bean class="org.springframework.beans.factory.config.PropertyPlaceHolderConfigurer >
        <property name="locations" value="xyz.properties" />
   </bean>