Dynamically compose DynamoDB Query Expression according to user input

Question

I'm writing an API endpoint to allow users to list items according to the parameters they pass in on the request body.

I want the partition key to be the only required parameter; clients will be allowed to pass zero or more key-value pairs to achieve the desired level of granularity in their query.

My DynamoDB Table holds items with the following structure:

{
  "appName": { //PARTITION KEY
    "S": "APP_1"
  },
  "requestId": { // SORT KEY
    "S": "request_1224"
  },
  "creationTime": {
    "N": "1636332520679"
  },
  "resolver": {
    "S": "SOMEONES_ID"
  },
  "status": {
     "S": "PENDING"
  }
}

I have some working code, where the DynamoDBQueryExpression is hard-coded and I do have an idea of how to dynamically put together the Query Expression but I'm thinking of an ugly combination of for-loops and string manipulation.

Is there an elegant and clean way of dynamically putting together the DynamoDBQueryExpression?

Here's the starter code I have, for reference:

    Map<String, AttributeValue> eav = new HashMap<String, AttributeValue>();
    eav.put(":val1", new AttributeValue().withS(requestModel.getAppName()));
    eav.put(":val2", new AttributeValue().withS(accessRequestModel.getRequestStatus()));

    DynamoDBQueryExpression<RequestModel> queryExpression = new DynamoDBQueryExpression<RequestModel>()
            .withKeyConditionExpression("appName = :val1")
            .withFilterExpression("RequestStatus = :val2")
            .withExpressionAttributeValues(eav);

Just to be extra clear, see how I'm doing put and passing hard-coded values to withFilterConditionExpression –I'd like these values being passed dynamically according to client's input.

I'm using Java's AWS DynamoDB Mapper.

Dynamically compose DynamoDB Query Expression according to user input

0 Answers0