The Asset object is a child object of the Account object. You will need to get all related children (assets) from the case's parent Account. Also instead of using JSONGenerator you can directly serialize the list with JSON.serialize(). This is how I would solve this:
Create a wrapper class to hold the Case Id, Account Id and all Asset Names related to that account (as you described):
public class CaseWithAsset { public Id caseId; public Id accountId; public List <String> assetNames; }
Then in your constructor create a list that will hold multiple instances of this class:
List <CaseWithAsset> casesWithAssets = new List <CaseWithAsset> ();
The query on the Case object should only get the parent Account IDs:
List <Case> cases = [SELECT Id, AccountId FROM Case LIMIT 10];
Then follow the comments in the code below:
// Map the account Id to the related case and also create a placeholder for the asset names Map <Id, CaseWithAsset> accountIdToCaseWithAsset = new Map <Id, CaseWithAsset> (); // Go through each case in your list for (Case caseRecord : cases) { // Create new instance of the wrapper class CaseWithAsset caseWithAsset = new CaseWithAsset(); // Set the caseId and accountId (we know both at this stage) caseWithAsset.caseId = caseRecord.Id; caseWithAsset.accountId = caseRecord.AccountId; // Create an empty list that will hold all related asset names caseWithAsset.assetNames = new List <String> (); // Map this wrapper class instance to the accountId - it's the key that links this and the asset accountIdToCaseWithAsset.put(caseRecord.AccountId, caseWithAsset); } // Query the assets that are related to the account IDs from above for (Asset asset : [SELECT Id, Name, AccountId FROM Asset WHERE AccountId IN :accountIdToCaseWithAsset.keySet()]) { // Get the wrapper class instance from the map and add the asset name to the empty list accountIdToCaseWithAsset.get(asset.AccountId).assetNames.add(asset.Name); } // Serialize the list of wrapper class instances String jsonString = JSON.serialize(accountIdToCaseWithAsset.values());
I typed all this on the fly, it might have some typos or errors, but you can tweak it to your needs. It should get you started at least.
