Class Diagram for the Amazon Locker Service

We’ll create the class diagram for the Amazon Locker service. In the class diagram, we will first design the classes for the system, and then we will identify the relationship between classes according to the requirements gathered for the Amazon Locker service problem.

Components of an Amazon Locker service#

In this section, we’ll define the classes for an Amazon Locker service. As mentioned earlier, we are following the bottom-up approach to design a class diagram for the Amazon Locker service.

Item#

The Item class represents each item of the order. Every item contains an Id and the order’s quantity. The class representation is shown below:

Order#

The order placed by a customer is represented by the Order class. Every order has a unique Id, contains a list of items, and the delivery location of the order. The UML representation of a class is shown below:

Notification#

The notification is sent to the customer when an order is shipped. A Notification class has a customerId, orderId, and lockerId that specify the customer to whom the notification has to be sent, against the order the notification has to be sent, and the locker where the order has arrived, respectively. Moreover, this class contains a 6-digit code to open the locker. The class definition is given below:

Package and locker package#

The Package class represents the order which is packaged. The package is what can be kept in the locker. Each package has its own id and size. Moreover, the Package class has an Order type attribute to show against which order the package is sent. The class representation of Package is provided below:

The package that is kept inside the locker is represented by the LockerPackage class. Since an item kept in a locker has a validity of certain days, we have codeValidDays to keep track of this. This class contains lockerId to keep track of which locker contains a particular package. The code to open the locker for that package is stored in the code class and the packageDeliverTime class stores information about when the package is delivered to the particular locker.

The representation of the Package and LockerPackage classes is shown below:

Locker#

Since we are designing a locker service problem, we should have a Locker class. Every locker has its ID, size, and reference to the location ID. Moreover, the Locker class has a member, lockerState, to specify the present state of the locker. We can add a package to the locker and remove a package from the locker. The UML representation of a class is shown below:

Locker location#

A locker is kept at the location. Since a location may contain more than one locker, we have a list of lockers in the LockerLocation class. The longitude and latitude are used to store the location. According to the requirements, the specific locker is opened only for a particular period of time and the customer can only get a package from the locker if they visit the locker during the location timing. The openTime and closeTime variables store information about the timings applicable to the particular locker location.The representation of this class is given below:

Locker service#

The LockerService class is the main class of the Amazon Locker service system and contains a reference to the list of locker locations. The UML representation of the class is given below:

Enumerations#

The list of enumerations required in the Amazon Locker service is provided below:

LockerStatus: The locker status describes the current status of the locker, whether it is closed, booked, or available.

LockerSize: The locker size expresses the size of the locker, whether it is extra small, small, medium, large, extra large, or double extra large.

Relationship between the classes#

Now, we’ll discuss the relationships between the classes in the Amazon Locker service.

Association#

The class diagram has the following association relationships:

• The Notification class has a two-way association with the Locker and Order classes.

Composition#

The class diagram has the following composition relationships:

• The LockerService class comprises the LockerLocation class, which itself is composed of the Locker class and the LockerPackage class.

• The Package class is composed of the Order class which is composed of the Item class.

Inheritance#

The following classes show an inheritance relationship:

• The LockerPackage class extends the Package class.

Note: We have already discussed the inheritance relationship between classes in the component section above.

Class diagram of the Amazon Locker service#

Here’s the complete class diagram for our Amazon Locker service:

Design pattern#

In the Amazon Locker service, there are multiple lockers at the given locker location. There are also different locker locations which are specified by the customer. Therefore, the system assigns the most appropriate locker to the customer by considering the customer’s location, and locker size. Therefore, the Strategy design pattern can be applied here. Other than that, our system can also have the following strategies:

• OTP generation

• Random number generation

• Locker assignment

• Locker filtration

We can also use the Repository design pattern for the Amazon Locker system, where we can make the following repositories:

• Locker repository

• Package repository

AI-powered trainer#

At this stage, everything should be clear. If you encounter any confusion or ambiguity, feel free to utilize the interactive AI-enabled widget below to seek clarification. This tool is designed to assist you in strengthening your understanding of the concepts.

We have completed the class diagram of the Amazon Locker service according to the requirements. Now, let's design its sequence diagram in the next lesson.