What is interceptor?

1. Interceptors are an objects that dynamically intercept Action invocation.
2.  It is invoked at the preprocessing and postprocessing of a request.
3.  Interceptors provide a developer way to encapsulate common functionality in a re-usable that from one or more Action.
4.  It is perform validations, exception handling, logger, intermediate results etc.

What is abstraction?

Abstraction is a process of hiding implementation and showing only functionally to the user. 

What is the relation between ValueStack and OGNL ?

ValueStack is a place where all the data related to action and action itself store. OGNL is a mean which the data in ValueStack is manipulated.

Different Modes of autowiring

There are five type of auto wiring in Spring:

• no : no autowire
• byName : Autowiring by property name, means bean matching property name is autowired.
• byType : Bean having type as that of property type is autowired.
• constructor : Similar to byType just that the property is in constructor.
• autodetect :  Spring is allowed to select autowiring from byType and constructor

Spring Autowiring

• By Autowiring , Spring injects dependencies without having to specify those explicitly.
• Spring inspects bean factory contents and establishes relationships amongst collaborating beans. To implement it,just add autowire property in xml configuration.

What are the important Spring beans life cycle methods?

There are two important beans life cycle methods.

1. setup
2. teardown

setup - It is called when bean is load into the container.
teardown - It is called when bean is unloaded from the container.