Scan all records of a Amazon DynamoDB table using a Java Code

Upasana | September 19, 2019 | 1 min read | 1,966 views | AWS Tutorials


Amazon DynamoDB Record Scanning

Sometimes we need to download all records from a remote dynamod db table for backup purpose. Amazon DynamoDB provides mechanism to scan and retrieve all records using ScanRequest.

DownloadRecords.java
public void downloadAllRecords() throws InterruptedException, IOException {
        final Object[] FILE_HEADER = {"id", "userId", "createdDate"};
        CSVFormat csvFormat = CSVFormat.DEFAULT.withRecordSeparator("\n");
        CSVPrinter csvPrinter = new CSVPrinter(new FileWriter(tableName + ".csv"), csvFormat);
        csvPrinter.printRecord(FILE_HEADER);

        ScanRequest scanRequest = new ScanRequest()
                .withTableName(tableName)
                .withConsistentRead(false)
                .withLimit(100)
                .withAttributesToGet("id", "userId", "createdDate");
        int counter = 0;
        do {
            ScanResult result = client.scan(scanRequest);
            Map<String, AttributeValue> lastEvaluatedKey = result.getLastEvaluatedKey();
            for (Map<String, AttributeValue> item : result.getItems()) {
                List record = new ArrayList();
                System.out.println(item);
                AttributeValue userIdAttribute = item.getOrDefault("userId", new AttributeValue());
                AttributeValue idAttribute = item.getOrDefault("id", new AttributeValue());
                AttributeValue createdDateAttribute = item.getOrDefault("createdDate", new AttributeValue());
                record.add(idAttribute.getS());
                record.add(userIdAttribute.getS());
                record.add(createdDateAttribute.getS());
                csvPrinter.printRecord(record);
                TimeUnit.MILLISECONDS.sleep(50);
            }
            scanRequest.setExclusiveStartKey(lastEvaluatedKey); (1)
        } while (scanRequest.getExclusiveStartKey() != null);
        csvPrinter.flush();
        csvPrinter.close();
        System.out.println("CSV file generated successfully.");
    }
1 The primary key of the first item that this operation will evaluate. Use the value that was returned for LastEvaluatedKey in the previous operation.

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