How to update item by Composite Primary Key in Dynamodb

Question

I have a table called friends:

Friend 1 | Friend 2 | Status

Friend 1 is my HASH attribute and Friend 2 is my range attribute.

I would like to update an item's staus attribute where friend 1 = 'Bob' and friend 2 = 'Joe'. Reading through the documentation on http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/JavaDocumentAPICRUDExample.html I can only see how to update an item by 1 key, how do I include the other key?

Answer 1

Here you go:

DynamoDBQueryExpression<Reply> queryExpression = new DynamoDBQueryExpression<Reply>()
            .withKeyConditionExpression("Id = :val1 and ReplyDateTime > :val2")
            .withExpressionAttributeValues(
...

where Id is the Hash Key and ReplyDateTime is the Range Key.

Reference: http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.QueryScanExample.html

Answer 2

I'm writing example where you can make update of multiple item in single table. I have primary key as id and range key as Datetime. Actually there is no feature available in dynamodb so what i'm doing here is first query all the variable with hash key and range key of which i want to make update. Once all data are stored in List then loading data with it's hash key and rangekey and changing or updating field using set and save it. Since I'm editing in hash key so, hash key original will be there we need to delete it. If you need to update in next attribute no need. I haven't added deleting code write yourself. You can query if you have confusion your entry with hash key will be still and new entry with new hash key will be added. Code is below:

public static void main(String[] args) {
    AmazonDynamoDBClient client = new AmazonDynamoDBClient();
    DynamoDBMapper mapper = new DynamoDBMapper(client);
    client.setEndpoint("http://localhost:8000/");
    String fromDate = "2016-01-13";
    String toDate = "2016-02-05";
    User user = new User();
    user.setId("YourHashKey");
    LocalDate frmdate = LocalDate.parse(fromDate, DateTimeFormatter.ISO_LOCAL_DATE);
    LocalDate todate = LocalDate.parse(toDate, DateTimeFormatter.ISO_LOCAL_DATE);
    LocalDateTime startfrm = frmdate.atStartOfDay();
    LocalDateTime endto = todate.atTime(23, 59, 59);
    Condition rangeCondition = new Condition().withComparisonOperator(ComparisonOperator.BETWEEN.toString()).withAttributeValueList(new AttributeValue().withS(startfrm.toString()), new AttributeValue().withS(endto.toString()));
    DynamoDBQueryExpression<User> queryExpression = new DynamoDBQueryExpression<User>().withHashKeyValues(user).withRangeKeyCondition("DATETIME", rangeCondition);
    List<User> latestReplies = mapper.query(User.class, queryExpression);
    for (User in : latestReplies) {
        System.out.println(" Hashid: " + in.getId() + " DateTime: " + in.getDATETIME() + "location:" + in.getLOCID());
        User ma = mapper.load(User.class, in.getId(), in.getDATETIME());
        ma.setLOCID("Ohelig");
        mapper.save(ma);
    }
}