Container, Dependency and IoC

Question 1

What is Dependency Injection

Answer 1

A process whereby a framework establishes relationships between different parts of an application.

Question 2

What are advantages of dependency injection

Answer 2

• Reduced coupling, cohesion, boilerplate code

- Increases testability, reusability, maintainability

Question 3

What is an interface

Answer 3

Is a reference type, can contain constants, method signatures, default/static methods

Question 4

Advantages of an interface

Answer 4

• Allows for decoupling, modularization, handling of groups of objects

Question 5

Why are Interfaxes recommended by Spring

Answer 5

• Increased Testability
• Allows for Jdk Proxying
• Easier switching of Spring bean implementation

Question 6

Stereotype Annotations

Answer 6

@Component
@Controller
@RestController
@Repository
@Service
@Configuration

Question 7

Bean scopes

Answer 7

singleton
 - Single Bean instance 
prototype
 - Each Time an instance is created
request 
session
application 
websocket

Question 8

Limitations of JDK Dynamic Proxies

Answer 8

• requires proxied object to implement at least one interface
• only methods found the interface are available in the proxy
• does not support self invocations

Question 9

Limitations of CGLIB Proxies

Answer 9

• Proxied object non final
• Methods in proxied object non final
• Does not support self invocations
• Third-party library

Question 10

Advantage Proxy object

Answer 10

• Can add power to existing beans

- Separation to business logic

Question 11

Disadvantages Proxy Object

Answer 11

• Not obvious where a method invocation is handled when proxy objects are used
• Multiple layers of proxy objects -> developers need to take into account the order
• Overhead
• Identity issues

Question 12

Three Typical Cross Cutting Concerns

Answer 12

• Logging
• Caching
• Security
• Data Validation
• Transaction management
• Error handling
• Monitoring

Question 13

Which problems does AOP solve

Answer 13

• Code duplication

- Avoding mixing of concerns

Question 14

Join Point

Answer 14

A join point is a point in the execution of a program at which additional behavior can be inserted using AOP

Question 15

Pointcut

Answer 15

A pointcut selects one or more join points

Question 16

How does Spring solve a cross cutting concern

Answer 16

Spring uses proxy objects to implement the method invocation interception part of AOP.

Question 17

How many advice types does Spring support

Answer 17

• Before advice
• After returning advice
• After throwing advice
• After advice
• Around advice

Question 18

Jdbc Template

Answer 18

Is a Spring class that simplifies the use of JDBC by implementing Workflows for querying, updating, ..

Question 19

Benefits of the JDBC Template

Answer 19

• Simplification
• Handles Exceptions
• Translates Exceptions
• Avoid common mistakes

Question 20

Callback

Answer 20

A callback is code or reference to a piece of code that is passed as an argument to a method that, at some point during the execution of the methods, will call the code passed as an argument.

Question 21

Transaction

Answer 21

A transaction is an operation that consists of a number of tasks that takes place as a single unit - either all tasks are performed or no tasks are performed.

Question 22

ACID principle

Answer 22

• Atomicity
  
  • The changes within a
    transaction are either all
    applied or none applied
• Consistency
  
  • Any integrity constraints are not violated
• Isolation
  
  • Translations don’t effect each other
• Durability
  
  • Changes applied as the result of a
    successfully completed transaction are
    durable

Question 23

Transaction isolation level

Answer 23

Determine how the changes within a transaction are visible to other users and systems accessing the database prior to the transaction being commited.