Menu
Amazon DynamoDB
Developer Guide (API Version 2012-08-10)

DynamoDB Streams Low-Level API: Java Example

Note

The code on this page is not exhaustive and does not handle all scenarios for consuming DynamoDB Streams. The recommended way to consume Stream records from DynamoDB is through the Kinesis Adapter using the Kinesis Client Library (KCL), as described in Using the DynamoDB Streams Kinesis Adapter to Process Stream Records.

This section contains a Java program that shows DynamoDB Streams in action. The program does the following:

  1. Creates a DynamoDB table with a stream enabled.

  2. Describes the stream settings for this table.

  3. Modify data in the table.

  4. Describe the shards in the stream.

  5. Read the stream records from the shards.

  6. Clean up.

When you run the program, you will see output similar to the following:

Issuing CreateTable request for TestTableForStreams Waiting for TestTableForStreams to be created... Current stream ARN for TestTableForStreams: arn:aws:dynamodb:us-east-2:123456789012:table/TestTableForStreams/stream/2018-03-20T16:49:55.208 Stream enabled: true Update view type: NEW_AND_OLD_IMAGES Performing write activities on TestTableForStreams Processing item 1 of 100 Processing item 2 of 100 Processing item 3 of 100 ... Processing item 100 of 100 Shard: {ShardId: shardId-1234567890-...,SequenceNumberRange: {StartingSequenceNumber: 01234567890...,},} Shard iterator: EjYFEkX2a26eVTWe... ApproximateCreationDateTime: Tue Mar 20 09:50:00 PDT 2018,Keys: {Id={N: 1,}},NewImage: {Message={S: New item!,}, Id={N: 1,}},SequenceNumber: 100000000003218256368,SizeBytes: 24,StreamViewType: NEW_AND_OLD_IMAGES} {ApproximateCreationDateTime: Tue Mar 20 09:50:00 PDT 2018,Keys: {Id={N: 1,}},NewImage: {Message={S: This item has changed,}, Id={N: 1,}},OldImage: {Message={S: New item!,}, Id={N: 1,}},SequenceNumber: 200000000003218256412,SizeBytes: 56,StreamViewType: NEW_AND_OLD_IMAGES} {ApproximateCreationDateTime: Tue Mar 20 09:50:00 PDT 2018,Keys: {Id={N: 1,}},OldImage: {Message={S: This item has changed,}, Id={N: 1,}},SequenceNumber: 300000000003218256413,SizeBytes: 36,StreamViewType: NEW_AND_OLD_IMAGES} ... Deleting the table... Demo complete

Example

// Copyright 2012-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved. // Licensed under the Apache License, Version 2.0. package com.amazon.codesamples; import java.util.ArrayList; import java.util.Arrays; import java.util.HashMap; import java.util.List; import java.util.Map; import com.amazonaws.AmazonClientException; import com.amazonaws.auth.DefaultAWSCredentialsProviderChain; import com.amazonaws.regions.Regions; import com.amazonaws.services.dynamodbv2.AmazonDynamoDB; import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder; import com.amazonaws.services.dynamodbv2.AmazonDynamoDBStreams; import com.amazonaws.services.dynamodbv2.AmazonDynamoDBStreamsClientBuilder; import com.amazonaws.services.dynamodbv2.model.AttributeAction; import com.amazonaws.services.dynamodbv2.model.AttributeDefinition; import com.amazonaws.services.dynamodbv2.model.AttributeValue; import com.amazonaws.services.dynamodbv2.model.AttributeValueUpdate; import com.amazonaws.services.dynamodbv2.model.CreateTableRequest; import com.amazonaws.services.dynamodbv2.model.DescribeStreamRequest; import com.amazonaws.services.dynamodbv2.model.DescribeStreamResult; import com.amazonaws.services.dynamodbv2.model.DescribeTableResult; import com.amazonaws.services.dynamodbv2.model.GetRecordsRequest; import com.amazonaws.services.dynamodbv2.model.GetRecordsResult; import com.amazonaws.services.dynamodbv2.model.GetShardIteratorRequest; import com.amazonaws.services.dynamodbv2.model.GetShardIteratorResult; import com.amazonaws.services.dynamodbv2.model.KeySchemaElement; import com.amazonaws.services.dynamodbv2.model.KeyType; import com.amazonaws.services.dynamodbv2.model.ProvisionedThroughput; import com.amazonaws.services.dynamodbv2.model.Record; import com.amazonaws.services.dynamodbv2.model.Shard; import com.amazonaws.services.dynamodbv2.model.ShardIteratorType; import com.amazonaws.services.dynamodbv2.model.StreamSpecification; import com.amazonaws.services.dynamodbv2.model.StreamViewType; import com.amazonaws.services.dynamodbv2.util.TableUtils; public class StreamsLowLevelDemo { public static void main(String args[]) throws InterruptedException { AmazonDynamoDB dynamoDBClient = AmazonDynamoDBClientBuilder .standard() .withRegion(Regions.US_EAST_2) .withCredentials(new DefaultAWSCredentialsProviderChain()) .build(); AmazonDynamoDBStreams streamsClient = AmazonDynamoDBStreamsClientBuilder .standard() .withRegion(Regions.US_EAST_2) .withCredentials(new DefaultAWSCredentialsProviderChain()) .build(); // Create a table, with a stream enabled String tableName = "TestTableForStreams"; ArrayList<AttributeDefinition> attributeDefinitions = new ArrayList<>( Arrays.asList(new AttributeDefinition() .withAttributeName("Id") .withAttributeType("N"))); ArrayList<KeySchemaElement> keySchema = new ArrayList<>( Arrays.asList(new KeySchemaElement() .withAttributeName("Id") .withKeyType(KeyType.HASH))); // Partition key StreamSpecification streamSpecification = new StreamSpecification() .withStreamEnabled(true) .withStreamViewType(StreamViewType.NEW_AND_OLD_IMAGES); CreateTableRequest createTableRequest = new CreateTableRequest().withTableName(tableName) .withKeySchema(keySchema).withAttributeDefinitions(attributeDefinitions) .withProvisionedThroughput(new ProvisionedThroughput() .withReadCapacityUnits(10L) .withWriteCapacityUnits(10L)) .withStreamSpecification(streamSpecification); System.out.println("Issuing CreateTable request for " + tableName); dynamoDBClient.createTable(createTableRequest); System.out.println("Waiting for " + tableName + " to be created..."); try { TableUtils.waitUntilActive(dynamoDBClient, tableName); } catch (AmazonClientException e) { e.printStackTrace(); } // Print the stream settings for the table DescribeTableResult describeTableResult = dynamoDBClient.describeTable(tableName); String streamArn = describeTableResult.getTable().getLatestStreamArn(); System.out.println("Current stream ARN for " + tableName + ": " + describeTableResult.getTable().getLatestStreamArn()); StreamSpecification streamSpec = describeTableResult.getTable().getStreamSpecification(); System.out.println("Stream enabled: " + streamSpec.getStreamEnabled()); System.out.println("Update view type: " + streamSpec.getStreamViewType()); System.out.println(); // Generate write activity in the table System.out.println("Performing write activities on " + tableName); int maxItemCount = 100; for (Integer i = 1; i <= maxItemCount; i++) { System.out.println("Processing item " + i + " of " + maxItemCount); // Write a new item Map<String, AttributeValue> item = new HashMap<>(); item.put("Id", new AttributeValue().withN(i.toString())); item.put("Message", new AttributeValue().withS("New item!")); dynamoDBClient.putItem(tableName, item); // Update the item Map<String, AttributeValue> key = new HashMap<>(); key.put("Id", new AttributeValue().withN(i.toString())); Map<String, AttributeValueUpdate> attributeUpdates = new HashMap<>(); attributeUpdates.put("Message", new AttributeValueUpdate() .withAction(AttributeAction.PUT) .withValue(new AttributeValue() .withS("This item has changed"))); dynamoDBClient.updateItem(tableName, key, attributeUpdates); // Delete the item dynamoDBClient.deleteItem(tableName, key); } // Get all the shard IDs from the stream. Note that DescribeStream returns // the shard IDs one page at a time. String lastEvaluatedShardId = null; do { DescribeStreamResult describeStreamResult = streamsClient.describeStream( new DescribeStreamRequest() .withStreamArn(streamArn) .withExclusiveStartShardId(lastEvaluatedShardId)); List<Shard> shards = describeStreamResult.getStreamDescription().getShards(); // Process each shard on this page for (Shard shard : shards) { String shardId = shard.getShardId(); System.out.println("Shard: " + shard); // Get an iterator for the current shard GetShardIteratorRequest getShardIteratorRequest = new GetShardIteratorRequest() .withStreamArn(streamArn) .withShardId(shardId) .withShardIteratorType(ShardIteratorType.TRIM_HORIZON); GetShardIteratorResult getShardIteratorResult = streamsClient.getShardIterator(getShardIteratorRequest); String currentShardIter = getShardIteratorResult.getShardIterator(); // Shard iterator is not null until the Shard is sealed (marked as READ_ONLY). // To prevent running the loop until the Shard is sealed, which will be on average // 4 hours, we process only the items that were written into DynamoDB and then exit. int processedRecordCount = 0; while (currentShardIter != null && processedRecordCount < maxItemCount) { System.out.println(" Shard iterator: " + currentShardIter.substring(380)); // Use the shard iterator to read the stream records GetRecordsResult getRecordsResult = streamsClient.getRecords(new GetRecordsRequest() .withShardIterator(currentShardIter)); List<Record> records = getRecordsResult.getRecords(); for (Record record : records) { System.out.println(" " + record.getDynamodb()); } processedRecordCount += records.size(); currentShardIter = getRecordsResult.getNextShardIterator(); } } // If LastEvaluatedShardId is set, then there is // at least one more page of shard IDs to retrieve lastEvaluatedShardId = describeStreamResult.getStreamDescription().getLastEvaluatedShardId(); } while (lastEvaluatedShardId != null); // Delete the table System.out.println("Deleting the table..."); dynamoDBClient.deleteTable(tableName); System.out.println("Demo complete"); } }