CODEWITHSUNDEEP
javaamazon-web-servicesamazon-dynamodb
aoak
aoak

Reputation: 1013

Conditional write item if attribute not equals with DynamoDBMapper

Is it possible to do a conditional write/update using DynamoDB mapper when you want to have condition like: Write if attribute is not equal to X? I want to do a conditional write that does something like this:

DynamoRecord record = mapper.load(DynamoRecord.class, hashKey);
if (record.getSomeAttr() != terminationValue) {
    mapper.save(newRecord);
}

The attribute always exists. It can have multiple values and represents a condition after which the updates to the record should stop.

I read this article and AWS documentation and a bunch of other posts but seems like only == operator is supported along with exists check. Is it possible to do a != conditional write using a mapper? If so, any pointers are much appreciated.

Thanks.

Summary from @notionquest's answer

  1. Use ComparisonOperator.NE
  2. If the attribute is a boolean, annotate it using @DynamoDBNativeBoolean for correct results while using ExpectedAttributeValue(new AttributeValue().withBool(true)). See here for details.

Upvotes: 3

Views: 7101

Answers (2)

neomatrix
neomatrix

Reputation: 59

DynamoDBSaveExpression saveExpression = new DynamoDBSaveExpression();
Map expected = new HashMap();
expected.put("Status",new ExpectedAttributeValue(new AttributeValue('NE')));
saveExpression.setExpected(expected);
dynamoDBMapper.save(obj, saveExpression);

Upvotes: -1

notionquest
notionquest

Reputation: 39176

Please use "withComparisonOperator(ComparisonOperator.NE)" for NOTEQUALS condition. Refer the below example.

DynamoDBSaveExpression saveExpression = new DynamoDBSaveExpression();
       Map expected = new HashMap();
       expected.put("Status", 
          new ExpectedAttributeValue(new AttributeValue(status)).withComparisonOperator(ComparisonOperator.NE));
saveExpression.setExpected(expected);
dynamoDBMapper.save(obj, saveExpression);

Upvotes: 5

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