Overview of persisting a domain model - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 97

TimeRange

Address

dayofWeek
openingTime
closingTime

street1
street2
city
state
zip

Payment
Information

*

0. .1

0. .1

PendingOrder-
PaymentInformation

Pendi ngOrder-A ddress Restaurant -TimeRange

PendingOrder-
Restaurant

0. .1

<<interface >>
Coupon

PendingOrder Restaurant

PendingOrder
-Coupon

code
validFrom
validTo

Date deliveryTime

0. .1 name

serviceArea:Set < String >

PendingOrder-
PendingOrderLineItem

Restaurant -MenuItem

* PendingOrderLineItem-

MenuItem

MenuItem

PendingOrder
LineItem

FreeShipping
Coupon

Percentage
DiscountCoupon

name
description
price

quantity

1

code
minimum

code
minimum
percentage

Figure 4.1 Part of the domain model for the Food to Go application

in a straightforward way into the database concepts. As a result, deciding how
each object, field, and relationship in the domain model is stored in the database
is a difficult problem. In this section, you will learn how.

4.1.1 Mapping classes

The central concept in a domain model is, of course, the class, which describes
the structure and behavior of its instances or objects. There are three main ways
to map a class to a database schema:

Map a class to its own table.

■

Map a class to some other class's table.

■

Map a class to multiple tables.

■

Let's look at each one.