DynamoDb now supports running a local test version of the Database. This is how you connect to it with the AWS Java SDK.

int port = 8800;
ClientConfiguration config = new ClientConfiguration().withProtocol(Protocol.HTTP);
AWSCredentials creds = new BasicAWSCredentials("test","madeup");
AmazonDynamoDBClient client = AmazonDynamoDBClient(creds,config);
client.setEndpoint("localhost:"+port);