import java.util.List;
import java.util.Map;
import java.util.HashMap;
import java.util.ArrayList;
import java.util.stream.Collectors;

import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.BatchGetItemRequest;
import software.amazon.awssdk.services.dynamodb.model.BatchGetItemResponse;
import software.amazon.awssdk.services.dynamodb.model.KeysAndAttributes;
import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
import software.amazon.awssdk.enhanced.dynamodb.DynamoDbTable;
import software.amazon.awssdk.enhanced.dynamodb.TableSchema;

private List<CgfpUpstreamEventDAO> findByIds(List<String> eventIds) {
    // Prepare the list of key maps for the batch get request.
    // Assumes the table's partition key is named "eventId".
    List<Map<String, AttributeValue>> keys = new ArrayList<>();
    for (String eventId : eventIds) {
        Map<String, AttributeValue> key = new HashMap<>();
        key.put("eventId", AttributeValue.builder().s(eventId).build());
        keys.add(key);
    }
    
    // Specify the projection expression to retrieve only "attribute1" and "attribute2".
    // If these attribute names conflict with DynamoDB reserved words,
    // you may need to use ExpressionAttributeNames.
    String projectionExpression = "attribute1, attribute2";
    
    // Build the KeysAndAttributes object with keys and the projection.
    KeysAndAttributes keysAndAttributes = KeysAndAttributes.builder()
            .keys(keys)
            .projectionExpression(projectionExpression)
            .build();
    
    // Create the request items map with the table name as the key.
    // Assumes cgfpUpstreamEventTable is an instance of DynamoDbTable<CgfpUpstreamEventDAO>.
    Map<String, KeysAndAttributes> requestItems = new HashMap<>();
    requestItems.put(cgfpUpstreamEventTable.tableName(), keysAndAttributes);
    
    // Build and execute the low-level batchGetItem request.
    BatchGetItemRequest batchGetItemRequest = BatchGetItemRequest.builder()
            .requestItems(requestItems)
            .build();
    
    BatchGetItemResponse response = dynamoDbClient.batchGetItem(batchGetItemRequest);
    
    // Retrieve the list of returned items (as maps of AttributeValue).
    List<Map<String, AttributeValue>> items =
            response.responses().get(cgfpUpstreamEventTable.tableName());
    
    // Use the table's TableSchema to convert the raw attribute maps into DAO objects.
    TableSchema<CgfpUpstreamEventDAO> tableSchema = cgfpUpstreamEventTable.tableSchema();
    
    // Map each item to an instance of CgfpUpstreamEventDAO.
    return items.stream()
            .map(tableSchema::mapToItem)
            .collect(Collectors.toList());
}