Question 201954 in Amazon Web Sevices Question posted in
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Amazon web services – incompatible types: com.amazonaws.waiters.WaiterParameters is not a functional interface

When I create a dynamodb table, I try to use waiters to wait AWS service to complete its action.

CreateTableRequest createRequest = new CreateTableRequest()
            .withTableName(tableName);
    
CreateTableResult createResult = dynamoDbClient.createTable(createRequest);
dynamoDbClient.waiters().tableExists().run(() -> new DescribeTableRequest(tableName));
return dynamoDB.getTable(tableName);

But I get:

incompatible types: com.amazonaws.waiters.WaiterParameters is not a functional interface

I’m new to Java, what’s a functional interface? How can I get around this problem?

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2

Answers


  1. Chosen as BEST ANSWER
    0

    Dividing into 2 rows seems to solve the problem:

    Waiter<DescribeTableRequest> waiter = dynamoDbClient.waiters().tableExists();
waiter.run(new WaiterParameters<>(new DescribeTableRequest(tableName)));

  2. 0

    Use AWS SDK for Java V2, not the AWS SDK for Java V1 – which is no longer recommended to use as specified on this AWS page.

    You can use Waiters easily using the Amazon Dynamo V2 API. See this code example.

    //snippet-sourcedescription:[CreateTable.java demonstrates how to create an Amazon DynamoDB table by using a waiter.]
//snippet-keyword:[SDK for Java v2]
//snippet-service:[Amazon DynamoDB]

/*
   Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
   SPDX-License-Identifier: Apache-2.0
*/

package com.example.dynamodb;

// snippet-start:[dynamodb.java2.create_table.import]
import software.amazon.awssdk.auth.credentials.ProfileCredentialsProvider;
import software.amazon.awssdk.core.waiters.WaiterResponse;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.AttributeDefinition;
import software.amazon.awssdk.services.dynamodb.model.CreateTableRequest;
import software.amazon.awssdk.services.dynamodb.model.CreateTableResponse;
import software.amazon.awssdk.services.dynamodb.model.DescribeTableRequest;
import software.amazon.awssdk.services.dynamodb.model.DescribeTableResponse;
import software.amazon.awssdk.services.dynamodb.model.DynamoDbException;
import software.amazon.awssdk.services.dynamodb.model.KeySchemaElement;
import software.amazon.awssdk.services.dynamodb.model.KeyType;
import software.amazon.awssdk.services.dynamodb.model.ProvisionedThroughput;
import software.amazon.awssdk.services.dynamodb.model.ScalarAttributeType;
import software.amazon.awssdk.services.dynamodb.waiters.DynamoDbWaiter;
// snippet-end:[dynamodb.java2.create_table.import]

/**
 * Before running this Java V2 code example, set up your development environment, including your credentials.
 *
 * For more information, see the following documentation topic:
 *
 * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html
 */
public class CreateTable {

    public static void main(String[] args) {

        final String usage = "n" +
            "Usage:n" +
            "    <tableName> <key>nn" +
            "Where:n" +
            "    tableName - The Amazon DynamoDB table to create (for example, Music3).nn" +
            "    key - The key for the Amazon DynamoDB table (for example, Artist).n" ;

       if (args.length != 2) {
           System.out.println(usage);
           System.exit(1);
       }

       String tableName = args[0];
       String key = args[1];
       System.out.println("Creating an Amazon DynamoDB table "+tableName +" with a simple primary key: " +key );

       ProfileCredentialsProvider credentialsProvider = ProfileCredentialsProvider.create();
       Region region = Region.US_EAST_1;
       DynamoDbClient ddb = DynamoDbClient.builder()
           .credentialsProvider(credentialsProvider)
           .region(region)
           .build();

       String result = createTable(ddb, tableName, key);
       System.out.println("New table is "+result);
       ddb.close();
    }

    // snippet-start:[dynamodb.java2.create_table.main]
    public static String createTable(DynamoDbClient ddb, String tableName, String key) {
        DynamoDbWaiter dbWaiter = ddb.waiter();
        CreateTableRequest request = CreateTableRequest.builder()
            .attributeDefinitions(AttributeDefinition.builder()
                .attributeName(key)
                .attributeType(ScalarAttributeType.S)
                .build())
            .keySchema(KeySchemaElement.builder()
                .attributeName(key)
                .keyType(KeyType.HASH)
                .build())
            .provisionedThroughput(ProvisionedThroughput.builder()
                .readCapacityUnits(new Long(10))
                .writeCapacityUnits(new Long(10))
                .build())
            .tableName(tableName)
            .build();

        String newTable ="";
        try {
            CreateTableResponse response = ddb.createTable(request);
            DescribeTableRequest tableRequest = DescribeTableRequest.builder()
                .tableName(tableName)
                .build();

            // Wait until the Amazon DynamoDB table is created.
            WaiterResponse<DescribeTableResponse> waiterResponse = dbWaiter.waitUntilTableExists(tableRequest);
            waiterResponse.matched().response().ifPresent(System.out::println);
            newTable = response.tableDescription().tableName();
            return newTable;

        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
       return "";
    }
    // snippet-end:[dynamodb.java2.create_table.main]
}

    To read more about waiter and the AWS SDK for Java V2, see:

    Using waiters in the AWS SDK for Java 2.x

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