com.amazonaws.services.dynamodbv2.model.BatchWriteItemRequest Java Examples

/**
 * calls splitResultIntoBatches to turn the SegmentedScanResult into several
 * BatchWriteItemRequests and then submits them as individual jobs to the
 * ExecutorService.
 */
@Override
public Future<Void> writeResult(SegmentedScanResult result) {
    Future<Void> jobSubmission = null;
    List<BatchWriteItemRequest> batches = splitResultIntoBatches(
            result.getScanResult(), tableName);
    Iterator<BatchWriteItemRequest> batchesIterator = batches.iterator();
    while (batchesIterator.hasNext()) {
        try {
            jobSubmission = exec
                    .submit(new DynamoDBConsumerWorker(batchesIterator
                            .next(), client, rateLimiter, tableName));
        } catch (NullPointerException npe) {
            throw new NullPointerException(
                    "Thread pool not initialized for LogStashExecutor");
        }
    }
    return jobSubmission;
}
 

private void commitPartial(List<WriteRequest> list) {
  	Timer t = new Timer();
Map<String, List<WriteRequest>> map = new HashMap<>();
map.put(getTenant().getName(), list);
BatchWriteItemResult result = m_client.batchWriteItem(new BatchWriteItemRequest(map));
int retry = 0;
while(result.getUnprocessedItems().size() > 0) {
	if(retry == RETRY_SLEEPS.length) throw new RuntimeException("All retries failed");
	m_logger.debug("Committing {} unprocessed items, retry: {}", result.getUnprocessedItems().size(), retry + 1);
	try {
		Thread.sleep(RETRY_SLEEPS[retry++]);
	} catch (InterruptedException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
  		result = m_client.batchWriteItem(new BatchWriteItemRequest(result.getUnprocessedItems()));
}
m_logger.debug("Committed {} writes in {}", list.size(), t);
list.clear();
  }
 

static List<Map<String, AttributeValue>> generateTestData(String tableName, int numOfItems) {
  BatchWriteItemRequest batchWriteItemRequest =
      generateBatchWriteItemRequest(tableName, numOfItems);

  dynamoDBClient.batchWriteItem(batchWriteItemRequest);
  ScanResult scanResult = dynamoDBClient.scan(new ScanRequest().withTableName(tableName));

  List<Map<String, AttributeValue>> items = scanResult.getItems();
  Assert.assertEquals(numOfItems, items.size());
  return items;
}
 

public BatchWritePointResult batchWritePoints(List<PutPointRequest> putPointRequests) {
	BatchWriteItemRequest batchItemRequest = new BatchWriteItemRequest();
	List<WriteRequest> writeRequests = new ArrayList<WriteRequest>();
	for (PutPointRequest putPointRequest : putPointRequests) {
		long geohash = S2Manager.generateGeohash(putPointRequest.getGeoPoint());
		long hashKey = S2Manager.generateHashKey(geohash, config.getHashKeyLength());
		String geoJson = GeoJsonMapper.stringFromGeoObject(putPointRequest.getGeoPoint());

		PutRequest putRequest = putPointRequest.getPutRequest();
		AttributeValue hashKeyValue = new AttributeValue().withN(String.valueOf(hashKey));
		putRequest.getItem().put(config.getHashKeyAttributeName(), hashKeyValue);
		putRequest.getItem().put(config.getRangeKeyAttributeName(), putPointRequest.getRangeKeyValue());
		AttributeValue geohashValue = new AttributeValue().withN(Long.toString(geohash));
		putRequest.getItem().put(config.getGeohashAttributeName(), geohashValue);
		AttributeValue geoJsonValue = new AttributeValue().withS(geoJson);
		putRequest.getItem().put(config.getGeoJsonAttributeName(), geoJsonValue);			
		
		WriteRequest writeRequest = new WriteRequest(putRequest);
		writeRequests.add(writeRequest);
	}
	Map<String, List<WriteRequest>> requestItems = new HashMap<String, List<WriteRequest>>();
	requestItems.put(config.getTableName(), writeRequests);
	batchItemRequest.setRequestItems(requestItems);
	BatchWriteItemResult batchWriteItemResult = config.getDynamoDBClient().batchWriteItem(batchItemRequest);
	BatchWritePointResult batchWritePointResult = new BatchWritePointResult(batchWriteItemResult);
	return batchWritePointResult;
}
 

@Test
public void testRetries() throws Throwable {
  thrown.expectMessage("Error writing to DynamoDB");

  final List<WriteRequest> writeRequests = DynamoDBIOTestHelper.generateWriteRequests(numOfItems);

  AmazonDynamoDB amazonDynamoDBMock = Mockito.mock(AmazonDynamoDB.class);
  Mockito.when(amazonDynamoDBMock.batchWriteItem(Mockito.any(BatchWriteItemRequest.class)))
      .thenThrow(new AmazonDynamoDBException("Service unavailable"));

  pipeline
      .apply(Create.of(writeRequests))
      .apply(
          DynamoDBIO.<WriteRequest>write()
              .withWriteRequestMapperFn(
                  (SerializableFunction<WriteRequest, KV<String, WriteRequest>>)
                      writeRequest -> KV.of(tableName, writeRequest))
              .withRetryConfiguration(
                  DynamoDBIO.RetryConfiguration.create(4, Duration.standardSeconds(10)))
              .withAwsClientsProvider(AwsClientsProviderMock.of(amazonDynamoDBMock)));

  try {
    pipeline.run().waitUntilFinish();
  } catch (final Pipeline.PipelineExecutionException e) {
    // check 3 retries were initiated by inspecting the log before passing on the exception
    expectedLogs.verifyWarn(String.format(DynamoDBIO.Write.WriteFn.RETRY_ATTEMPT_LOG, 1));
    expectedLogs.verifyWarn(String.format(DynamoDBIO.Write.WriteFn.RETRY_ATTEMPT_LOG, 2));
    expectedLogs.verifyWarn(String.format(DynamoDBIO.Write.WriteFn.RETRY_ATTEMPT_LOG, 3));
    throw e.getCause();
  }
  fail("Pipeline is expected to fail because we were unable to write to DynamoDB.");
}
 

/**
 * Callable class that when called will try to write a batch to a DynamoDB
 * table. If the write returns unprocessed items it will exponentially back
 * off until it succeeds.
 */
public DynamoDBConsumerWorker(BatchWriteItemRequest batchWriteItemRequest,
        AmazonDynamoDBClient client, RateLimiter rateLimiter,
        String tableName) {
    this.batch = batchWriteItemRequest;
    this.client = client;
    this.rateLimiter = rateLimiter;
    this.tableName = tableName;
    this.exponentialBackoffTime = BootstrapConstants.INITIAL_RETRY_TIME_MILLISECONDS;
}
 

/**
 * Writes to DynamoDBTable using an exponential backoff. If the
 * batchWriteItem returns unprocessed items then it will exponentially
 * backoff and retry the unprocessed items.
 */
public List<ConsumedCapacity> runWithBackoff(BatchWriteItemRequest req) {
    BatchWriteItemResult writeItemResult = null;
    List<ConsumedCapacity> consumedCapacities = new LinkedList<ConsumedCapacity>();
    Map<String, List<WriteRequest>> unprocessedItems = null;
    boolean interrupted = false;
    try {
        do {
            writeItemResult = client.batchWriteItem(req);
            unprocessedItems = writeItemResult.getUnprocessedItems();
            consumedCapacities
                    .addAll(writeItemResult.getConsumedCapacity());

            if (unprocessedItems != null) {
                req.setRequestItems(unprocessedItems);
                try {
                    Thread.sleep(exponentialBackoffTime);
                } catch (InterruptedException ie) {
                    interrupted = true;
                } finally {
                    exponentialBackoffTime *= 2;
                    if (exponentialBackoffTime > BootstrapConstants.MAX_EXPONENTIAL_BACKOFF_TIME) {
                        exponentialBackoffTime = BootstrapConstants.MAX_EXPONENTIAL_BACKOFF_TIME;
                    }
                }
            }
        } while (unprocessedItems != null && unprocessedItems.get(tableName) != null);
        return consumedCapacities;
    } finally {
        if (interrupted) {
            Thread.currentThread().interrupt();
        }
    }
}
 

/**
 * Splits up a ScanResult into a list of BatchWriteItemRequests of size 25
 * items or less each.
 */
public static List<BatchWriteItemRequest> splitResultIntoBatches(
        ScanResult result, String tableName) {
    List<BatchWriteItemRequest> batches = new LinkedList<BatchWriteItemRequest>();
    Iterator<Map<String, AttributeValue>> it = result.getItems().iterator();

    BatchWriteItemRequest req = new BatchWriteItemRequest()
            .withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL);
    List<WriteRequest> writeRequests = new LinkedList<WriteRequest>();
    int i = 0;
    while (it.hasNext()) {
        PutRequest put = new PutRequest(it.next());
        writeRequests.add(new WriteRequest(put));

        i++;
        if (i == BootstrapConstants.MAX_BATCH_SIZE_WRITE_ITEM) {
            req.addRequestItemsEntry(tableName, writeRequests);
            batches.add(req);
            req = new BatchWriteItemRequest()
                    .withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL);
            writeRequests = new LinkedList<WriteRequest>();
            i = 0;
        }
    }
    if (i > 0) {
        req.addRequestItemsEntry(tableName, writeRequests);
        batches.add(req);
    }
    return batches;
}
 

/**
 * Test that a ScanResult splits into the correct number of batches.
 */
@Test
public void splitResultIntoBatchesTest() {
    final double numItems = 111.0;

    String tableName = "test tableName";

    ScanResult scanResult = new ScanResult();
    List<Map<String, AttributeValue>> items = new LinkedList<Map<String, AttributeValue>>();
    for (int i = 0; i < numItems; i++) {
        Map<String, AttributeValue> sampleScanResult = new HashMap<String, AttributeValue>();
        sampleScanResult.put("key", new AttributeValue("attribute value "
                + i));
        items.add(sampleScanResult);
    }
    scanResult.setItems(items);

    SegmentedScanResult result = new SegmentedScanResult(scanResult, 0);

    replayAll();
    List<BatchWriteItemRequest> batches = DynamoDBConsumer
            .splitResultIntoBatches(result.getScanResult(), tableName);
    assertEquals(Math.ceil(numItems / BootstrapConstants.MAX_BATCH_SIZE_WRITE_ITEM),
            batches.size(), 0.0);

    verifyAll();
}
 

@Override
public BatchWriteItemResult batchWriteItem(BatchWriteItemRequest arg0)
        throws AmazonServiceException, AmazonClientException {
    throw new UnsupportedOperationException("Use the underlying client instance instead");
}
 

@Override
public BatchWriteItemResult batchWriteItem(BatchWriteItemRequest batchWriteItemRequest) {
	throw new UnsupportedOperationException();
}
 

@Override
public BatchWriteItemResult batchWriteItem(BatchWriteItemRequest request) throws AmazonServiceException, AmazonClientException {
    return getBackend().batchWriteItem(request);
}
 

@Override
public BatchWriteItemResult batchWriteItem(BatchWriteItemRequest arg0)
        throws AmazonServiceException, AmazonClientException {
    throw new UnsupportedOperationException("Use the underlying client instance instead");
}
 

private static void writeMultipleItemsBatchWrite() {
    try {                    
        
       // Create a map for the requests in the batch
       Map<String, List<WriteRequest>> requestItems = new HashMap<String, List<WriteRequest>>();
        
       // Create a PutRequest for a new Forum item
       Map<String, AttributeValue> forumItem = new HashMap<String, AttributeValue>();
       forumItem.put("Name", new AttributeValue().withS("Amazon RDS"));
       forumItem.put("Threads", new AttributeValue().withN("0"));
    
       List<WriteRequest> forumList = new ArrayList<WriteRequest>();
       forumList.add(new WriteRequest().withPutRequest(new PutRequest().withItem(forumItem)));
       requestItems.put(table1Name, forumList);
       
       // Create a PutRequest for a new Thread item
       Map<String, AttributeValue> threadItem = new HashMap<String, AttributeValue>();
       threadItem.put("ForumName", new AttributeValue().withS("Amazon RDS"));
       threadItem.put("Subject", new AttributeValue().withS("Amazon RDS Thread 1"));
       threadItem.put("Message", new AttributeValue().withS("ElasticCache Thread 1 message"));
       threadItem.put("KeywordTags", new AttributeValue().withSS(Arrays.asList("cache", "in-memory")));
    
       List<WriteRequest> threadList = new ArrayList<WriteRequest>();
       threadList.add(new WriteRequest().withPutRequest(new PutRequest().withItem(threadItem)));
       
       // Create a DeleteRequest for a Thread item
       Map<String, AttributeValue> threadDeleteKey = new HashMap<String, AttributeValue>(); 
       threadDeleteKey.put("ForumName", new AttributeValue().withS("Amazon S3"));
       threadDeleteKey.put("Subject", new AttributeValue().withS("S3 Thread 100"));
       
       threadList.add(new WriteRequest().withDeleteRequest(new DeleteRequest().withKey(threadDeleteKey)));
       requestItems.put(table2Name, threadList);
       
       BatchWriteItemResult result;
       BatchWriteItemRequest batchWriteItemRequest = new BatchWriteItemRequest()
           .withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL);
       
       do {
           System.out.println("Making the request.");
                           
           batchWriteItemRequest.withRequestItems(requestItems);
           result = client.batchWriteItem(batchWriteItemRequest);
           
           // Print consumed capacity units
           for(ConsumedCapacity consumedCapacity : result.getConsumedCapacity()) {
                String tableName = consumedCapacity.getTableName();
                Double consumedCapacityUnits = consumedCapacity.getCapacityUnits();
                System.out.println("Consumed capacity units for table " + tableName + ": " + consumedCapacityUnits);
           }
           
           // Check for unprocessed keys which could happen if you exceed provisioned throughput
           System.out.println("Unprocessed Put and Delete requests: \n" + result.getUnprocessedItems());
           requestItems = result.getUnprocessedItems();
       } while (result.getUnprocessedItems().size() > 0);
                    
    }  catch (AmazonServiceException ase) {
        System.err.println("Failed to retrieve items: ");
        ase.printStackTrace(System.err);
    }  

}
 

private static void writeMultipleItemsBatchWrite() {
     try {
                   
// Begin syntax extract
         
         
// Create a map for the requests in the batch
Map<String, List<WriteRequest>> requestItems = new HashMap<String, List<WriteRequest>>();
 
// Create a PutRequest for a new Forum item
Map<String, AttributeValue> forumItem = new HashMap<String, AttributeValue>();
forumItem.put("Name", new AttributeValue().withS("Amazon RDS"));
forumItem.put("Threads", new AttributeValue().withN("0"));

List<WriteRequest> forumList = new ArrayList<WriteRequest>();
forumList.add(new WriteRequest().withPutRequest(new PutRequest().withItem(forumItem)));
requestItems.put("Forum", forumList);

// Create a PutRequest for a new Thread item
Map<String, AttributeValue> threadItem = new HashMap<String, AttributeValue>();
threadItem.put("ForumName", new AttributeValue().withS("Amazon RDS"));
threadItem.put("Subject", new AttributeValue().withS("Amazon RDS Thread 1"));

List<WriteRequest> threadList = new ArrayList<WriteRequest>();
threadList.add(new WriteRequest().withPutRequest(new PutRequest().withItem(threadItem)));

// Create a DeleteRequest for a Thread item
Map<String, AttributeValue> threadDeleteKey = new HashMap<String, AttributeValue>(); 
threadDeleteKey.put("ForumName", new AttributeValue().withS("Some hash attribute value"));
threadDeleteKey.put("Subject", new AttributeValue().withS("Some range attribute value"));

threadList.add(new WriteRequest().withDeleteRequest(new DeleteRequest().withKey(threadDeleteKey)));
requestItems.put("Thread", threadList);

BatchWriteItemRequest batchWriteItemRequest = new BatchWriteItemRequest();

System.out.println("Making the request.");
                     
batchWriteItemRequest.withRequestItems(requestItems);
client.batchWriteItem(batchWriteItemRequest);

// End syntax extract

                     
     }  catch (AmazonServiceException ase) {
         System.err.println("Failed to retrieve items: ");
         ase.printStackTrace(System.err);
     }  

 }
 

private void writeBatch(final boolean async) {
  final List<WriteRequest> batch;

  if (batchedItems.size() <= NUM_ITEMS) {
    batch = batchedItems;
  } else {
    batch = batchedItems.subList(0, NUM_ITEMS + 1);
  }
  final Map<String, List<WriteRequest>> writes = new HashMap<>();
  writes.put(tableName, new ArrayList<>(batch));
  if (async) {

    /**
     * To support asynchronous batch write a async handler is created Callbacks are provided for
     * success and error. As there might be unprocessed items on failure, they are retried
     * asynchronously Keep track of futures, so that they can be waited on during "flush"
     */
    final BatchWriteItemRequest batchRequest = new BatchWriteItemRequest(writes);
    final Future<BatchWriteItemResult> future =
        client.batchWriteItemAsync(
            batchRequest,
            new AsyncHandler<BatchWriteItemRequest, BatchWriteItemResult>() {

              @Override
              public void onError(final Exception exception) {
                LOGGER.warn(
                    "Unable to get response from Dynamo-Async Write " + exception.toString());
                futureMap.remove(batchRequest);
                return;
              }

              @Override
              public void onSuccess(
                  final BatchWriteItemRequest request,
                  final BatchWriteItemResult result) {
                retryAsync(result.getUnprocessedItems());
                if (futureMap.remove(request) == null) {
                  LOGGER.warn(" Unable to delete BatchWriteRequest from futuresMap ");
                }
              }
            });

    futureMap.put(batchRequest, future);
  } else {
    final BatchWriteItemResult response =
        client.batchWriteItem(new BatchWriteItemRequest(writes));
    retry(response.getUnprocessedItems());
  }

  batch.clear();
}
 

public BatchWriteItemResult batchWriteItem(final BatchWriteItemRequest batchRequest) throws BackendException {
    int count = 0;
    for (Entry<String, List<WriteRequest>> entry : batchRequest.getRequestItems().entrySet()) {
        final String tableName = entry.getKey();
        final List<WriteRequest> requests = entry.getValue();
        count += requests.size();
        if (count > BATCH_WRITE_MAX_NUMBER_OF_ITEMS) {
            throw new IllegalArgumentException("cant have more than 25 requests in a batchwrite");
        }
        for (final WriteRequest request : requests) {
            if ((request.getPutRequest() != null) == (request.getDeleteRequest() != null)) {
                throw new IllegalArgumentException("Exactly one of PutRequest or DeleteRequest must be set in each WriteRequest in a batch write operation");
            }
            final int wcu;
            final String apiName;
            if (request.getPutRequest() != null) {
                apiName = PUT_ITEM;
                final int bytes = calculateItemSizeInBytes(request.getPutRequest().getItem());
                wcu = computeWcu(bytes);
            } else { //deleterequest
                apiName = DELETE_ITEM;
                wcu = estimateCapacityUnits(apiName, tableName);
            }
            timedWriteThrottle(apiName, tableName, wcu);
        }
    }

    BatchWriteItemResult result;
    setUserAgent(batchRequest);
    final Timer.Context apiTimerContext = getTimerContext(BATCH_WRITE_ITEM, null /*tableName*/);
    try {
        result = client.batchWriteItem(batchRequest);
    } catch (Exception e) {
        throw processDynamoDbApiException(e, BATCH_WRITE_ITEM, null /*tableName*/);
    } finally {
        apiTimerContext.stop();
    }
    if (result.getConsumedCapacity() != null) {
        for (ConsumedCapacity ccu : result.getConsumedCapacity()) {
            meterConsumedCapacity(BATCH_WRITE_ITEM, ccu);
        }
    }
    return result;
}
 

static BatchWriteItemRequest generateBatchWriteItemRequest(String tableName, int numOfItems) {
  BatchWriteItemRequest batchWriteItemRequest = new BatchWriteItemRequest();
  batchWriteItemRequest.addRequestItemsEntry(tableName, generateWriteRequests(numOfItems));
  return batchWriteItemRequest;
}
 

private void flushBatch() throws IOException, InterruptedException {
  if (batch.isEmpty()) {
    return;
  }

  try {
    // Since each element is a KV<tableName, writeRequest> in the batch, we need to group them
    // by tableName
    Map<String, List<WriteRequest>> mapTableRequest =
        batch.stream()
            .collect(
                Collectors.groupingBy(
                    KV::getKey, Collectors.mapping(KV::getValue, Collectors.toList())));

    BatchWriteItemRequest batchRequest = new BatchWriteItemRequest();
    mapTableRequest
        .entrySet()
        .forEach(
            entry -> batchRequest.addRequestItemsEntry(entry.getKey(), entry.getValue()));

    Sleeper sleeper = Sleeper.DEFAULT;
    BackOff backoff = retryBackoff.backoff();
    int attempt = 0;
    while (true) {
      attempt++;
      try {
        client.batchWriteItem(batchRequest);
        break;
      } catch (Exception ex) {
        // Fail right away if there is no retry configuration
        if (spec.getRetryConfiguration() == null
            || !spec.getRetryConfiguration().getRetryPredicate().test(ex)) {
          DYNAMO_DB_WRITE_FAILURES.inc();
          LOG.info(
              "Unable to write batch items {} due to {} ",
              batchRequest.getRequestItems().entrySet(),
              ex);
          throw new IOException("Error writing to DynamoDB (no attempt made to retry)", ex);
        }

        if (!BackOffUtils.next(sleeper, backoff)) {
          throw new IOException(
              String.format(
                  "Error writing to DynamoDB after %d attempt(s). No more attempts allowed",
                  attempt),
              ex);
        } else {
          // Note: this used in test cases to verify behavior
          LOG.warn(String.format(RETRY_ATTEMPT_LOG, attempt), ex);
        }
      }
    }
  } finally {
    batch.clear();
  }
}
 

private static void writeMultipleItemsBatchWrite() {
    try {

        // Create a map for the requests in the batch
        Map<String, List<WriteRequest>> requestItems = new HashMap<String, List<WriteRequest>>();

        // Create a PutRequest for a new Forum item
        Map<String, AttributeValue> forumItem = new HashMap<String, AttributeValue>();
        forumItem.put("Name", new AttributeValue().withS("Amazon RDS"));
        forumItem.put("Threads", new AttributeValue().withN("0"));

        List<WriteRequest> forumList = new ArrayList<WriteRequest>();
        forumList.add(new WriteRequest().withPutRequest(new PutRequest().withItem(forumItem)));
        requestItems.put(table1Name, forumList);

        // Create a PutRequest for a new Thread item
        Map<String, AttributeValue> threadItem = new HashMap<String, AttributeValue>();
        threadItem.put("ForumName", new AttributeValue().withS("Amazon RDS"));
        threadItem.put("Subject", new AttributeValue().withS("Amazon RDS Thread 1"));
        threadItem.put("Message", new AttributeValue().withS("ElastiCache Thread 1 message"));
        threadItem.put("KeywordTags", new AttributeValue().withSS(Arrays.asList("cache", "in-memory")));

        List<WriteRequest> threadList = new ArrayList<WriteRequest>();
        threadList.add(new WriteRequest().withPutRequest(new PutRequest().withItem(threadItem)));

        // Create a DeleteRequest for a Thread item
        Map<String, AttributeValue> threadDeleteKey = new HashMap<String, AttributeValue>();
        threadDeleteKey.put("ForumName", new AttributeValue().withS("Amazon S3"));
        threadDeleteKey.put("Subject", new AttributeValue().withS("S3 Thread 100"));

        threadList.add(new WriteRequest().withDeleteRequest(new DeleteRequest().withKey(threadDeleteKey)));
        requestItems.put(table2Name, threadList);

        BatchWriteItemResult result;
        BatchWriteItemRequest batchWriteItemRequest = new BatchWriteItemRequest()
            .withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL);

        do {
            System.out.println("Making the request.");

            batchWriteItemRequest.withRequestItems(requestItems);
            result = client.batchWriteItem(batchWriteItemRequest);

            // Print consumed capacity units
            for (ConsumedCapacity consumedCapacity : result.getConsumedCapacity()) {
                String tableName = consumedCapacity.getTableName();
                Double consumedCapacityUnits = consumedCapacity.getCapacityUnits();
                System.out.println("Consumed capacity units for table " + tableName + ": " + consumedCapacityUnits);
            }

            // Check for unprocessed keys which could happen if you exceed
            // provisioned throughput
            System.out.println("Unprocessed Put and Delete requests: \n" + result.getUnprocessedItems());
            requestItems = result.getUnprocessedItems();
        } while (result.getUnprocessedItems().size() > 0);

    }
    catch (AmazonServiceException ase) {
        System.err.println("Failed to retrieve items: ");
        ase.printStackTrace(System.err);
    }

}
 

private static void writeMultipleItemsBatchWrite() {
    try {

        // Begin syntax extract

        // Create a map for the requests in the batch
        Map<String, List<WriteRequest>> requestItems = new HashMap<String, List<WriteRequest>>();

        // Create a PutRequest for a new Forum item
        Map<String, AttributeValue> forumItem = new HashMap<String, AttributeValue>();
        forumItem.put("Name", new AttributeValue().withS("Amazon RDS"));
        forumItem.put("Threads", new AttributeValue().withN("0"));

        List<WriteRequest> forumList = new ArrayList<WriteRequest>();
        forumList.add(new WriteRequest().withPutRequest(new PutRequest().withItem(forumItem)));
        requestItems.put("Forum", forumList);

        // Create a PutRequest for a new Thread item
        Map<String, AttributeValue> threadItem = new HashMap<String, AttributeValue>();
        threadItem.put("ForumName", new AttributeValue().withS("Amazon RDS"));
        threadItem.put("Subject", new AttributeValue().withS("Amazon RDS Thread 1"));

        List<WriteRequest> threadList = new ArrayList<WriteRequest>();
        threadList.add(new WriteRequest().withPutRequest(new PutRequest().withItem(threadItem)));

        // Create a DeleteRequest for a Thread item
        Map<String, AttributeValue> threadDeleteKey = new HashMap<String, AttributeValue>();
        threadDeleteKey.put("ForumName", new AttributeValue().withS("Some partition key value"));
        threadDeleteKey.put("Subject", new AttributeValue().withS("Some sort key value"));

        threadList.add(new WriteRequest().withDeleteRequest(new DeleteRequest().withKey(threadDeleteKey)));
        requestItems.put("Thread", threadList);

        BatchWriteItemRequest batchWriteItemRequest = new BatchWriteItemRequest();

        System.out.println("Making the request.");

        batchWriteItemRequest.withRequestItems(requestItems);
        client.batchWriteItem(batchWriteItemRequest);

        // End syntax extract

    }
    catch (AmazonServiceException ase) {
        System.err.println("Failed to retrieve items: ");
        ase.printStackTrace(System.err);
    }

}