Three example use cases for custom REST and SOAP interfaces on the Force.com platform are given: 1) Allowing multiple external parties to log leads without duplicates, 2) Exposing a complex business process, and 3) Allowing a mobile app to interact with complex data models. The benefits of custom interfaces are listed as transaction safety, lower latency, and exposing only necessary business logic and data. Caveats include tools not understanding custom interfaces and the need to write and test code. Best practices discussed include conscious API design, considering the user experience, working with platform capabilities, and thorough testing.

1. Designing custom REST and SOAP
interfaces on Force.com
Steven Herod, Technical Director (Australia), Cloud Sherpas
@sherod

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3. Steven Herod
Technical Director, Cloud Sherpas (Australia)
@sherod

4. Agenda
• Use cases for custom interfaces
• Upsides and downsides
• Code walkthrough
• Best Practices

5. 3 (example) use cases
• Multiple external parties need to log leads w/o duplicates
• Concern: Complex business requirements, or to understand
Salesforce.
• A complex business process now needs to be exposed
• Concern: Uncontrolled modification to underlying data could cause
havoc.
• Your mobile app needs to deal with a complex data model
• Concern: A lot of network traffic, complex business logic

6. Benefits
• Transaction safety – update multiple objects in a single request
• Lower latency - complete many activities in a single request
• Offers a narrow, service oriented, interface that allows you to
expose only the aspects of the business logic and data model
that are needed.
• More robust as it can be unit tested.
• A published and controlled interface specific to your business.

7. Caveats
• Your ETL Tool may not understand custom REST/SOAP interfaces with
Salesforce.
• An out of the box ‘Salesforce Adapter’ is not applicable here.
(Generic REST / SOAP should work however)
• You need to write code (and test coverage)
• What was ‘no effort’ on the Salesforce side now becomes a Software
Development process
• You have the request limits for you.
• Request size (3MB)
• SOQL query limits (100 per request)
• Record modification limits(10,000 records touched)

8. For and against

9. A real life example
Public Internet user clicks this button on a Heroku
Based website or a Mobile app
Salesforce needs to do this

13. Class structure

14. Best Practices
• Consciously design your API
• Think about it! Govern it! Consider every method/operation! Document it!
• Fight for the user
• Think: “What is easiest for the consumer of the interface?”
• Work with the platform
• Salesforce REST != REST purist
• Salesforce SOAP != WS-*
• Consider how you will manage testing with external parties
• Test data, test system availability…

15. Best practices
• Use Apex Wrapper Classes as Data Transfer Objects
• Refrain from sending or expecting sObjects or you may expose a lot of
internal details
• Use a Services layer
• Keep your business code out of the class that handles the public interface.
• Bake in versioning
• Consider if you need to make a change to your interface
• Unit test all the things
• The unit test is your insurance and means you can detect when declarative
changes affect your code

16. Best Practices
• Manage your transactions explicitly
• Especially if you do exception trapping
• Use @future if you need to.
• Shorten response times where its safe to go async
• Indicate in the Apex Class’s name it’s usage as a public interface
• Consider the error feedback
• What does a API consumer see if things go wrong?
• Program defensively
• Expect bad input

17. REST Specific query advice
• 1 Class per URL mapping = proliferation
• Don’t forget the Query String
• E.g. GET /LoanApplications/?daysSinceUpdate=5
• Watch your status codes and verbs!
• Use the right status code and the right verb (GET, PUT, POST)