Object modeling is a common practice in mobile applications. We present two methods for modeling objects backed by Amazon DynamoDB, the AWS Persistence Framework for Core Data and DynamoDBMapper. We cover the benefits and limitations of these two solutions and demonstrate sample applications built with both technologies.

4. Data displayed on
mobile device
Data stored in
DynamoDB

5. @DynamoDBTable(tableName = ”UserPreference")
public class UserPreference {
@DynamoDBHashKey(attributeName = "userId")
public int getUserId() {
return userId;
}
@DynamoDBAttribute(attributeName = "firstName")
public String getFirstName() {
return firstName;
}
@DynamoDBAttribute(attributeName = "lastName")
public String getLastName() {
return lastName;
}

7. // Create a client
AmazonDynamoDBClient ddb = new AmazonDynamoDBClient(creds);
// Create a mapping of values
HashMap item = new HashMap();
AttributeValue userId = new AttributeValue().withN(1337);
item.put("userId", userId);
AttributeValue firstName = new AttributeValue().withS("Bob");
item.put("firstName", firstName);
AttributeValue lastName = new AttributeValue().withS("Kinney");
item.put("lastName", lastName);
// Put the item in DynamoDB
PutItemRequest request = new PutItemRequest()
.withTableName("Prefs").withItem(item);
ddb.putItem(request);

8. // create our client and mapper
AmazonDynamoDBClient ddb = new
AmazonDynamoDBClient(credentials);
DynamoDBMapper mapper = new DynamoDBMapper(ddb);
// create our object, set metadata
UserPreference up = new UserPreference();
up.setUserId(1337);
up.setFirstName(“Bob”);
up.setLastName(“Kinney”);
// save to Amazon DynamoDB
mapper.save(up);
// load the object by key
up = mapper.load(UserPreference.class, 1337);

10. UserPreference
@DynamoDBTable
public class UserPreference {
…
}
Prefs
@DynamoDBTable(tableName = ”Prefs")
public class UserPreference {
…
}

11. @DynamoDBHashKey(attributeName = ”A") A
public int getUserId() {
return userId;
}

12. @DynamoDBAttribute(attributeName = ”B")
public String getFirstName() {
return firstName;
}
@DynamoDBAttribute(attributeName = ”C")
public String getLastName() {
B
return lastName;
} C
@DynamoDBIgnore
public String getFullName() {
return firstName + “ “ + lastName;
}

13. @DynamoDBHashKey(attributeName = "userId")
@DynamoDBAutoGeneratedKey
public int getUserId() {
return userId;
}
UserPreference up = new UserPreference();
up.setUserId(1337);
up.setFirstName(“Bob”);
up.setLastName(“Kinney”);

14. A A A
SAVE
B B B
1 1 2

15. A A
B
1
SAVE
B
3 !

16. public class ComplexObject {
@DynamoDBMarshalling(marshallerClass = Conv.class)
public ComplexType getComplex() { return complex; }
}
public class Conv implements DynamoDBMarshaller<ComplexType> {
public String marshall(ComplexType value) {
…
}
public ComplexType
unmarshall(Class<ComplexType> ct, String value) {
…
}
}

17. A C A
SAVE
B D B
C E C
D
E

18. A C A
SAVE
B D B
C E C

19. A C A
SAVE LOAD
B D B
C E C
C
D
E

20. A C A
SAVE LOAD
B D B
C E C

21. PRODUCTION DEVELOPMENT

23. What about iOS?

25. DEMO

26. Creating AWS Persistence Store
// Registers the AWSNSIncrementalStore
[NSPersistentStoreCoordinator
registerStoreClass:
[AWSPersistenceDynamoDBIncrementalStore class]
forStoreType:
AWSPersistenceDynamoDBIncrementalStoreType];
// Adds the store to the coordinator
[persistentStoreCoordinator
addPersistentStoreWithType:
AWSPersistenceDynamoDBIncrementalStoreType
configuration:nil URL:nil
options:options error:&error];

27. Creating an NSManagedObject
Checkin *checkin = (Checkin *)
[NSEntityDescription
insertNewObjectForEntityForName:@"Checkin”
inManagedObjectContext:managedObjectContext];
checkin.checkinId = [Utilities getUUID];
checkin.checkinTime = [NSDate date];
checkin.comment = @”First checkin”;
[managedObjectContext save:&error];

28. Loading NSManagedObject
// Create a fetch request
NSFetchRequest *request = [[NSFetchRequest alloc] init];
// Specify the entity
NSEntityDescription *entity =
[NSEntityDescription entityForName:@"Location"
inManagedObjectContext:managedObjectContext];
[request setEntity:entity];
// Execute the fetch
NSArray *fetchedResults =
[managedObjectContext executeFetchRequest:request
error:&error];

29. Other Operations
[managedObjectContext deleteObject:location];
[managedObjectContext refreshObject:location
mergeChanges:YES];

30. tableMapper = [NSDictionary dictionaryWithObjectsAndKeys:
@"AWS-Locations", @"Location”, nil];
AWS-Locations

31. hashKeys = [NSDictionary dictionaryWithObjectsAndKeys:
@"locationId", @"Location”, nil];
locationId

32. versions = [NSDictionary dictionaryWithObjectsAndKeys:
@"version", @"Location”, nil];
A A
B
1
SAVE
B
3 ?

33. http://developer.apple.com/library/ios/#documentation/Core
Data/Reference/NSMergePolicy_Class/Reference/Referen
ce.html

34. [[NSNotificationCenter defaultCenter]
addObserver:self
selector:@selector(mergeDeletedObject:)
name:AWSPersistenceDynamoDBObjectDeletedNotification
object:nil];
A
B
LOAD
!

35. @protocol AWSPersistenceDynamoDBIncrementalStoreDelegate
<NSObject>
@required
- (AmazonCredentials *)credentials;
@optional
- (void)handleAuthenticationFailure;
@end

38. https://forums.aws.amazon.com/
http://stackoverflow.com/tags/amazon-web-services
https://github.com/amazonwebservices/aws-sdk-for-ios
https://github.com/amazonwebservices/aws-sdk-for-android

39. http://aws.amazon.com/mobile/
http://aws.amazon.com/articles/3756417425850538
http://aws.amazon.com/articles/4435846131581972

40. We are sincerely eager to
hear your feedback on this
presentation and on re:Invent.
Please fill out an evaluation
form when you have a
chance.