Week 4

Question 1

What does DAO stand for? Where does the pattern come from?

Answer 1

Data Access Objects, comes from Core J2EE

Question 2

How does DAO work?

Answer 2

Separates business/domain layer from the data layer. Abstracts/encapsulates the data source and access to it.

Question 3

What data source functions are encapsulated by DAO?

Answer 3

CRUD - Create, Retrieve, Update, Delete

Question 4

The motivation behind the DAO pattern is isolated the _________/______ differences from the rest of the implementation.

Answer 4

business/domain.

You can easily change one part without changing the other.

Question 5

What pattern is commonly added to the DAO pattern?

Answer 5

Factory

Question 6

What are the 4 typical components of the DAO pattern?

Answer 6

Data source
Business/Domain object
Data Access Object
Data Transfer Object

Question 7

Name this: Could be linked to an RDBMS, LDAP, XML

Answer 7

Data Source

Question 8

Name this: Requires access to the Data Sources to obtain/store data

Answer 8

Domain or Business object

Keep in mind the access is not direct in this pattern

Question 9

Name this: Performs the CRUD operations for the program and abstracts the data source

Answer 9

DAO

Question 10

Name this: Encapsulates data sent between the DAO and Domain/business layer

Answer 10

DTO

Question 11

When would you use a DAO interface? Why?

Answer 11

When there are multiple entities in the Data Source.

Same interface to access all entities, you implement a DAO class for each entity

Ex. entity_nameDAO

Question 12

Should the Domain Object get “raw” exceptions from the Data Source? (Like SQLException)

Answer 12

No, the DAO should handle exceptions related to the Data Source and throw customer exceptions to the Domain Object

Question 13

What is the Value Object? (Not DTO, even if its called that by mistake)

Answer 13

A small (usually immutable) object that encapsulates a value, like money, time, date.

Question 14

The “bean” pattern is a programming convention. Explain

The constructor
Instance variables access modifiers
Getters and Setters
Serializable

Answer 14

no-arg public constructor
private instance vars
Getters and setters exist for each instance var
implements serializable

Question 15

What is the bean pattern used for? If you need introspection or notifications should you implement it?

Answer 15

Reusable components. If introspection and notifications are needed implement JavaBean API