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Table of Contents

Objective

  • grasp spring concepts
  • learn the theory behind the Spring framework

What is the Spring Framework?

  • it's a web framework for building web apps using java
  • released in 2004

Why Spring framework came out?

  • to solve complex configurations in a java enterprise edition that uses java enterprise beans (EJB)
  • also to enhance poor performance
  • create loosely coupled software

What is spring architecture?

  • spring introduces a layered architecture; each layer contains a set of modules (~20 modules)
  • through this layered architecture spring achieved one-stop-shop philosophy
  • Modules:
    1. Core: contains dependency injection and inversion of control which uses a factory design pattern
    2. Aspect-oriented programming: to remove cross-cutting concerns
    3. Data access: contains JDBC, ORM
    4. Web: contains servlets, web sockets

Spring beans

What is a bean?

  • Simply, a bean is a java object which is created and destroyed through spring IOC and DI

What is bean scope?

  • bean scope is responsible for deciding:

    1. How long will the bean live?
    2. How many instances will be created?
    Scope Description
    Singleton Default scope, create one instance per Spring container
    Prototype Create a new instance every time the bean is requested
    Request Single bean instance per HTTP request
    Session Single bean instance per HTTP session
    Global-session Single bean instance per global HTTP session

What is bean life-cycle?

What is Dependency Injection and Inversion of control?

  • It's a process of delegating instantiation and assembling objects into:
    1. XML files
    2. XML using annotations
    3. other java code
  • and to inject object dependencies you have to use:
    1. Constructor injection
    2. Setter injection

What is aspect-oriented programming?

  • it's a programming paradigm that aims to increase modularity by separating cross-cutting concerns
  • Steps:
    1. Define point-cut (logger, security) "cross-cutting concern"
    2. Define those points into something called aspect
    3. Define configuration for each aspect (when-where you want to call this aspect)

Spring MVC

What is spring MVC?

  • It's a spring framework for building web-apps by applying model-view-controller architectural style

Why to use spring MVC?

  • Separation of concerns which make your app able to:
    1. scale easily.
    2. be tested
    3. be developed in a fast and parallel fashion

Structure of spring MVC

Hibernate

What is hibernate?

  • It's an object-relational mapping that relies on a layer in between app and database to handle conversion between tables and classes
  • Java App ⇒ hibernate ⇒ JDBC ⇒ DB

What is an entity life-cycle?

  1. transient (un-tracked)
  2. persist (attached to the database so any change that happens will reflect on the database)
  3. detached
  4. removed

What is cascading and their types?

  • Apply the same changes-operations to related entities
  • Types:
    1. Save
    2. Delete
    3. Detach
    4. All
    5. Remove
    6. merge

Difference between eager and lazy loading

  • Eager: loads all data at once
  • Lazy: loads data whenever it's required-requested

Resources