Handlers, Pipelines, Plugins, Rules, Mappers (22%)

Question 1

Which design pattern follows the handler chain ?

Answer 1

The chain of responsibility design pattern

Question 2

What is the responsibility of each handler when its processing is complete ?

Answer 2

Calling the next handler in the chain or terminate the chain immediately

Question 3

What is the sole entry point into a handler ?

Answer 3

The “Execute” method

Question 4

Two handlers are part of the same handler chain if:

Answer 4

they both declare the same parameter and result object types

Question 5

True or false.

As a best practice, all handlers should inherit from the HandlerBase class ?

Answer 5

True

Question 6

Why do we need to decorate handlers with the DependencyName attribute ?

Answer 6

This allows the handler to be retrieved by name via the dependency locator.

Question 7

Which method should continue an handler chain or break it ?

Answer 7

The the Execute method

Question 8

What should be the last line of code of your handler to execute the next one?

Answer 8

return this.NextHandler.Execute(unitOfWork, parameter, result);

Question 9

What should be the last line of code of your handler to break the handler chain?

Answer 9

return result;

Question 10

What are mappers ?

Answer 10

Mappers are extension points of the Optimizely B2B Commerce platform.

Question 11

What is the purposes of mappers?

Answer 11

Bridge the gap between the API presentation layer and the business logic layer (services) for both input and output.

Question 12

Is it possible to inherit from Optimizely’s mapper classes ?

Answer 12

Yes

Question 13

When you derive from a mapper class, where are you allowed to read additional information from the HTTP request and provide the information to the parameters object that will be used during the next handler chain ?

Answer 13

In the MapParameter method

Question 14

True or false.

In a mapper, you should read information using the HttpContext directly in your handler chain extension?

Answer 14

False. The best practice is to collect all the information read from the HTTP request in the mapper and send it as properties to the parameters object for the handle chain.

Question 15

Which method of a mapper allows us to intervene on the feedback of the handler chain (service result) and to pass it to the response object (API model) ?

Answer 15

The MapResult method

Question 16

Where should the majority of customizations and modifications be located?

Answer 16

In the extensions of the handler chain and/or pipelines that are called during the execution of this handler chain.

Question 17

Where its the appropriate place to add properties to the API model, for any entity field that you would like to have available on the frontend ?

Answer 17

In a mapper class

Question 18

Where is the appropriate place to add “display” properties that can become handy on the frontend ?

Answer 18

In a mapper class

Question 19

Why should you move the logic of the private functions from the handler class to a service?

Answer 19

• The values that these methods compute are possibly reusable in other places in the application.
• Using a service will eliminate the duplication of code and make it usable elsewhere.
• The service is also testable with unit tests, if the logic is complex enough and you want to perform test coverage.

Question 20

Pipelines are very similar to handler chains. Which statements are not true ? Pick 2.

• Both follows the principles of the chain of responsibility design pattern.
• Both can interrupt the execution.
• A pipeline is made of classes, which are called “pipes” and handler chains are made of classes called handlers.
• No need to specify the DependencyName attribute on a pipe class
• The Execute method of an handler class simply returns the result.

Answer 20

Both can interrupt the execution is false.
Unlike a handler class, a pipe class cannot interrupt the execution of the rest of the pipeline.

The Execute method of an handler class simply returns the result is false.
The Execute method of a pipe class simply returns the result. No need to call the next pipe class.

Question 21

What is the responsibility of the mapper ?

Answer 21

The Mapper is responsible for transcribing the API Parameter to an object that the service layer can use, usually named ServiceParameter.

Question 22

What are the responsibilities of controllers?

Answer 22

Managing requests and responses

Question 23

True or False. Controllers are responsible to apply business logic?

Answer 23

False. They are responsible for managing the flow of the API request through the Mapper, then to the service, back into the mapper and send a response.

Question 24

Which are the 2 responsibilities of the mappers?

Answer 24

• Mapping objects from the presentation layer (API model) to objects that the service layer can use (Service Parameter)
• Mapping back the Service Result into an API model that the controller can send back into the response

Question 25

How do you create an handler chain?

Answer 25

Inject the HandlerFactory responsible for creating handler chains

Call the first Handler’s Execute method, which in turn will call the next Handler’s Execute method and so on