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LowLevelBatchGet.java

/** * Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * This file is licensed under the Apache License, Version 2.0 (the "License"). * You may not use this file except in compliance with the License. A copy of * the License is located at * * http://aws.amazon.com/apache2.0/ * * This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR * CONDITIONS OF ANY KIND, either express or implied. See the License for the * specific language governing permissions and limitations under the License. */ package com.amazonaws.codesamples.lowlevel; import java.io.IOException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import com.amazonaws.AmazonServiceException; import com.amazonaws.auth.profile.ProfileCredentialsProvider; import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient; import com.amazonaws.services.dynamodbv2.model.AttributeValue; import com.amazonaws.services.dynamodbv2.model.BatchGetItemRequest; import com.amazonaws.services.dynamodbv2.model.BatchGetItemResult; import com.amazonaws.services.dynamodbv2.model.KeysAndAttributes; public class LowLevelBatchGet { static AmazonDynamoDBClient client = new AmazonDynamoDBClient(new ProfileCredentialsProvider()); static String table1Name = "Forum"; static String table2Name = "Thread"; public static void main(String[] args) throws IOException { retrieveMultipleItemsBatchGet(); } private static void retrieveMultipleItemsBatchGet() { try { Map<String, KeysAndAttributes> requestItems = new HashMap<String, KeysAndAttributes>(); List<Map<String, AttributeValue>> tableKeys = new ArrayList<Map<String, AttributeValue>>(); Map<String, AttributeValue> key = new HashMap<String, AttributeValue>(); key.put("Name", new AttributeValue().withS("Amazon S3")); tableKeys.add(key); key = new HashMap<String, AttributeValue>(); key.put("Name", new AttributeValue().withS("Amazon DynamoDB")); tableKeys.add(key); requestItems.put(table1Name, new KeysAndAttributes().withKeys(tableKeys)); tableKeys = new ArrayList<Map<String, AttributeValue>>(); key = new HashMap<String, AttributeValue>(); key.put("ForumName", new AttributeValue().withS("Amazon DynamoDB")); key.put("Subject", new AttributeValue().withS("DynamoDB Thread 1")); tableKeys.add(key); key = new HashMap<String, AttributeValue>(); key.put("ForumName", new AttributeValue().withS("Amazon DynamoDB")); key.put("Subject", new AttributeValue().withS("DynamoDB Thread 2")); tableKeys.add(key); key = new HashMap<String, AttributeValue>(); key.put("ForumName", new AttributeValue().withS("Amazon S3")); key.put("Subject", new AttributeValue().withS("S3 Thread 1")); tableKeys.add(key); requestItems.put(table2Name, new KeysAndAttributes().withKeys(tableKeys)); BatchGetItemResult result; BatchGetItemRequest batchGetItemRequest = new BatchGetItemRequest(); do { System.out.println("Making the request."); batchGetItemRequest.withRequestItems(requestItems); result = client.batchGetItem(batchGetItemRequest); List<Map<String, AttributeValue>> table1Results = result.getResponses().get(table1Name); if (table1Results != null) { System.out.println("Items in table " + table1Name); for (Map<String, AttributeValue> item : table1Results) { printItem(item); } } List<Map<String, AttributeValue>> table2Results = result.getResponses().get(table2Name); if (table2Results != null) { System.out.println("\nItems in table " + table2Name); for (Map<String, AttributeValue> item : table2Results) { printItem(item); } } // Check for unprocessed keys which could happen if you exceed // provisioned // throughput or reach the limit on response size. for (Map.Entry<String, KeysAndAttributes> pair : result.getUnprocessedKeys().entrySet()) { System.out.println("Unprocessed key pair: " + pair.getKey() + ", " + pair.getValue()); } requestItems = result.getUnprocessedKeys(); } while (result.getUnprocessedKeys().size() > 0); } catch (AmazonServiceException ase) { System.err.println("Failed to retrieve items."); } } private static void printItem(Map<String, AttributeValue> attributeList) { for (Map.Entry<String, AttributeValue> item : attributeList.entrySet()) { String attributeName = item.getKey(); AttributeValue value = item.getValue(); System.out.println(attributeName + " " + (value.getS() == null ? "" : "S=[" + value.getS() + "]") + (value.getN() == null ? "" : "N=[" + value.getN() + "]") + (value.getB() == null ? "" : "B=[" + value.getB() + "]") + (value.getSS() == null ? "" : "SS=[" + value.getSS() + "]") + (value.getNS() == null ? "" : "NS=[" + value.getNS() + "]") + (value.getBS() == null ? "" : "BS=[" + value.getBS() + "] \n")); } } }

Sample Details

Service: dynamodb

Last tested:

Author: AWS

Type: full-example

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