如何从Android更新DynamoDB中的项目？

Question

The title describes the question that's been surrounding my pain for three days. How to update an item stored in DynamoDB from an Android app?

Below I left a list of links I already checked and implemented with unsuccessful results:

1 - https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/examples-dynamodb-items.html Result: it is strictly for java ee, not android

2 - https://docs.aws.amazon.com/aws-mobile/latest/developerguide/add-aws-mobile-nosql-database.html#add-aws-mobile-nosql-database-crud-update Result: creates a new item even though the "unique-user-id" parameter is clearly unique

3 - https://docs.aws.amazon.com/aws-mobile/latest/developerguide/how-to-nosql-integrate-an-existing-table.html Result: same as above, creates a new one

4 - https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.CRUDExample1.html Result: retrieves but creates a new one item

Answer 1

Thing I was doing kind of wrong: -Not including my sort (aka Range) key in my object to be send for the update.

For the rest: First, get your DynamoDBClient, I'd strongly suggest implementing a singleton pattern for calling this, I used the configuration.json in this case:

AWSMobileClient.getInstance().initialize(NewPatientActivity.this).execute();
    AWSCredentialsProvider credentialsProvider = AWSMobileClient.getInstance().getCredentialsProvider();
    AWSConfiguration configuration = AWSMobileClient.getInstance().getConfiguration();
    // Add code to instantiate a AmazonDynamoDBClient
    AmazonDynamoDBClient dynamoDBClient = new AmazonDynamoDBClient(credentialsProvider);

Then set an UpdateItemRequest like this:

//SET THE KEYS VALUES
HashMap<String, AttributeValue> key = new HashMap<String, AttributeValue>();
            key.put("your-partition-key", new AttributeValue().withS(value));
            key.put("your-sort-key-if-exists", new AttributeValue().withS(value));
//SET VALUES TO REPLACE OLD ONES
 Map<String, AttributeValue> expressionAttributeValues = new HashMap<String, AttributeValue>();
            expressionAttributeValues.put(":val1",new AttributeValue().withN(value1));
            expressionAttributeValues.put(":val2", new AttributeValue().withS(value2));
/*
IF YOU WANT TO READ THE JUST-UPDATED ITEM, HAVE THIS READY
            ReturnValue returnValues = ReturnValue.ALL_NEW;

*/
//SET THE UPDATEITEMREQUEST
      UpdateItemRequest updateItemRequest = new UpdateItemRequest()
                    .withTableName("your-table-name")
                    //KEYS DEFINED ABOVE                        
                    .withKey(key)
                    //SET WHERE TO UPDATE
                    .withUpdateExpression("set attr1 = :val1, attr2 = :val2")
                .withExpressionAttributeValues(expressionAttributeValues)
                   //INDICATE TO RETURN UPDATED ITEM                     
                  .withReturnValues(returnValues);
   //GET THE RESULT OF YOUR UPDATE AND EXECUTE IT
     UpdateItemResult result = your-dynamo-client.updateItem(updateItemRequest);
    //convert it to a string                
     Gson gson = new Gson();
     String x = gson.toJson(result);
    //Check it out                
     Log.e("RESULT :",x);

For further information, I elaborated this gist.