import com.amazonaws.services.dynamodbv2.document.BatchGetItemOutcome; //导入依赖的package包/类
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());
    }  

}