DocumentAPIBatchGet.java

/*
* Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* 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
*
* or in the "license" file accompanying this file. 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.document;

import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient;
import com.amazonaws.services.dynamodbv2.document.BatchGetItemOutcome;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.Item;
import com.amazonaws.services.dynamodbv2.document.TableKeysAndAttributes;
import com.amazonaws.services.dynamodbv2.model.KeysAndAttributes;

public class DocumentAPIBatchGet {
    
    static DynamoDB dynamoDB = new DynamoDB(new AmazonDynamoDBClient(
            new ProfileCredentialsProvider()));
            
    static String forumTableName = "Forum";
    static String threadTableName = "Thread";
    
    public static void main(String[] args) throws IOException {

        retrieveMultipleItemsBatchGet();  

    }

    private static void retrieveMultipleItemsBatchGet() {        
        
        try {
            
            TableKeysAndAttributes forumTableKeysAndAttributes = new TableKeysAndAttributes(forumTableName);
            forumTableKeysAndAttributes.addHashOnlyPrimaryKeys("Name", "Amazon S3", "Amazon DynamoDB");
            
            TableKeysAndAttributes threadTableKeysAndAttributes = new TableKeysAndAttributes(threadTableName);
            threadTableKeysAndAttributes.addHashAndRangePrimaryKeys("ForumName", "Subject", 
                "Amazon DynamoDB","DynamoDB Thread 1",
                "Amazon DynamoDB","DynamoDB Thread 2",
                "Amazon S3","S3 Thread 1");
            
             Map<String, TableKeysAndAttributes> requestItems = new HashMap<String, TableKeysAndAttributes>();
             requestItems.put(forumTableName, forumTableKeysAndAttributes);
             requestItems.put(threadTableName, threadTableKeysAndAttributes);
             
             System.out.println("Making the request.");

             BatchGetItemOutcome outcome = dynamoDB.batchGetItem(forumTableKeysAndAttributes,
                            threadTableKeysAndAttributes);

            do {

                for (String tableName : outcome.getTableItems().keySet()) {
                    System.out.println("Items in table " + tableName);
                    List<Item> items = outcome.getTableItems().get(tableName);
                    for (Item item : items) {
                        System.out.println(item.toJSONPretty());
                    }
                }
                
                // Check for unprocessed keys which could happen if you exceed provisioned
                // throughput or reach the limit on response size.
                
                Map<String, KeysAndAttributes> unprocessedKeys = outcome.getUnprocessedKeys();
            
                if (outcome.getUnprocessedKeys().size() == 0) {
                    System.out.println("No unprocessed keys found");
                } else {
                    System.out.println("Retrieving the unprocessed keys");
                    outcome = dynamoDB.batchGetItemUnprocessed(unprocessedKeys);
                }
                
            } while (outcome.getUnprocessedKeys().size() > 0);
 
 
        }  catch (Exception e) {
            System.err.println("Failed to retrieve items.");
            System.err.println(e.getMessage());
        }  

    }
    
}