REST Resources in Apex (@RestResource)

Every earlier lesson in this module was Apex reaching out to an external system. @RestResource does the opposite: it exposes an Apex class as a REST API endpoint that external systems can call into Salesforce — genuinely the reverse integration direction.

@RestResource(urlMapping='/accounts/*')
global with sharing class AccountRestService {
    @HttpGet
    global static Account getAccount() {
        RestRequest req = RestContext.request;
        String accountId = req.requestURI.substring(req.requestURI.lastIndexOf('/') + 1);
        return [SELECT Id, Name, Industry FROM Account WHERE Id = :accountId];
    }
}

1. @RestResource(urlMapping='/accounts/*') — names the URL path this class exposes.
2. global with sharing class AccountRestService { — global, not public — required for a REST resource, plus with sharing.
3. @HttpGet — marks the next method as handling GET requests.
4. global static Account getAccount() { — global and static, the required shape.
5. RestRequest req = RestContext.request; — the incoming request, made available via RestContext.
6. String accountId = req.requestURI.substring(req.requestURI.lastIndexOf('/') + 1); — pulls the Id out of the URL path itself (e.g. /accounts/001XX...).
7. return [SELECT Id, Name, Industry FROM Account WHERE Id = :accountId]; — the queried Account, returned directly as the response body.
8. } — closes the method.
9. } — closes the class.

@RestResource(urlMapping='/accounts/*') names the URL path; @HttpGet marks this specific method as handling GET requests to that path. Note global — REST resource classes and their methods must be global, since they're callable from entirely outside the org, a stricter exposure than even @AuraEnabled's public.

@RestResource(urlMapping='/accounts/*')
global with sharing class AccountRestService {
    @HttpPost
    global static Id createAccount(String name, String industry) {
        Account acc = new Account(Name = name, Industry = industry);
        insert acc;
        return acc.Id;
    }
}

1. @RestResource(urlMapping='/accounts/*') — the same URL path.
2. global with sharing class AccountRestService { — the same class (a real class would combine both methods).
3. @HttpPost — marks this method as handling POST requests instead.
4. global static Id createAccount(String name, String industry) { — parameters map automatically from the incoming JSON body's fields.
5. Account acc = new Account(Name = name, Industry = industry); — builds a new Account from the incoming data.
6. insert acc; — Module 19's DML, saving it.
7. return acc.Id; — the new record's Id, sent back as the response.
8. } — closes the method.
9. } — closes the class.

@HttpPost handles incoming POST requests — parameters here map automatically from the incoming request's JSON body (Lesson 2's JSON.deserialize concept, handled implicitly by the framework this time) onto the method's own parameters.