Question

因为我在亚马逊上遇到很多管道问题我决定用java来备份我的数据库。我的桌子是50GB然后我需要最好的方法来保存它。这是读取元素并将其写入文件的java代码：

public static void fetchItems() {
    try{
        FileWriter file=new FileWriter(path);
        ScanResult result = null;
        long sum=0;
        do{
            ScanRequest req = new ScanRequest();
            req.setTableName(dataTable);

            if(result != null){
                req.setExclusiveStartKey(result.getLastEvaluatedKey());
            }

            result = dynamoDB.scan(req);
            List<Map<String, AttributeValue>> rows = result.getItems();

            for(Map<String, AttributeValue> map : rows){
                try{
                    JSONObject json=new JSONObject(map);
                    file.write(json.toString());
                } catch (NumberFormatException e){
                    System.out.println(e.getMessage());
                } catch (IOException e) {
                    System.out.println(e.getMessage());

                }
            }
            sum+= result.getItems().size();
            System.out.println("Result size: " + sum);

        } while(result.getLastEvaluatedKey() != null);
        file.flush();
        file.close();
    }catch(IOException e){
        System.out.println(e.getMessage());

文件的扩展名以及如何保存数据？使用我的代码文件太大而且很多字段都是null（新JSONObject（map）的问题），有人有想法吗？在我找到的文件中写道：

{＆＃34; leaseOwner＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; B＆＃34;：空，＆＃34 ; S＆＃34;：＆＃34; IP-120-115-91-22346.eu-西1.compute.internal：ef5c43f7-f5b7-49cf-99e6-8601db2922e2＆＃34;＆＃34; N＆＃34 ;：空，＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃ 34; BOOL＆＃34;：空}＆＃34; leaseKey＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34; ：空，＆＃34; S＆＃34;：＆＃34; shardId-000000000002＆＃34;＆＃34; N＆＃34;：空，＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}＆＃34; ownerSwitchesSinceCheckpoint＆＃34;：{ ＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：空，＆＃34; N＆＃ 34;：＆＃34; 0＆＃34;＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}＆＃34;检查点＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：＆＃34; 49551567310479336289724454124452290401607015400753594402＆＃34;＆＃34; N＆＃34;：空，＆＃34; L＆＃34;：空＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL ＆＃34;：空}＆＃34; leaseCounter＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; B＆＃34;：空＆＃34; S＆＃34;：空，＆＃34; N＆＃34;：＆＃34; 34905＆＃34;＆＃34; L＆＃34;：空，＆＃34; NS＆＃34 ;:空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}} {＆＃34; leaseOwner＆＃34; {＆＃34 ; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：＆＃34; IP-120-115-91 -22346.eu-西1.compute.internal：ef5c43f7-f5b7-49cf-99e6-8601db2922e2＆＃34;＆＃34; N＆＃34;：空，＆＃34; L＆＃34;：空，＆＃ 34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}＆＃34; leaseKey＆＃34 ;：{＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：＆＃34; shardId -000000000000＆＃34;＆＃34; N＆＃34;：空，＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}＆＃34; ownerSwitchesSinceCheckpoint＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃ 34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：空，＆＃34; N＆＃34;：＆＃34; 0＆＃34;＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空} ＆＃34;检查点＆＃34; {＆＃34; S S＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; B＆＃34;：空，＆＃34; S＆＃34;：＆＃34; 49551567310434734799327392878132951190473279252744634370＆＃34;＆＃34 ; N＆＃34;：空，＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34 ;:空，＆＃34; BOOL＆＃34;：空}＆＃34; leaseCounter＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：空，＆＃34; N＆＃34;：＆＃34; 34913＆＃34;＆＃34; L＆＃34;：空，＆＃34 ; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}} {＆＃34; leaseOwner＆＃34 ;：{＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：＆＃34; IP -120-115-91-22346.eu-西1.compute.internal：ef5c43f7-f5b7-49cf-99e6-8601db2922e2＆＃34;＆＃34; N＆＃34;：空，＆＃34; L＆＃34 ;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}，＆＃34; leaseKey＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34; ：＆＃34; shardId-000000000001＆＃34;＆＃34; N＆＃34;：空，＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}＆＃34; ownerSwitchesSinceCheckpoi NT＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; B＆＃34;：空，＆＃34; S＆＃34;：空，＆＃34; N＆＃34;：＆＃34; 0＆＃34;＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}＆＃34;检查点＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：＆＃34; 49551567310457035544525923501292620796040147120590684178＆＃34;＆＃34; N＆＃34;：空，＆＃34;升＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34; M＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}，＆＃34; leaseCounter＆＃34; {＆＃34; SS＆＃34;：空，＆＃34; BS＆＃34;：空，＆＃34; b＆＃34;：空，＆＃34; S＆＃34;：空，＆＃34; N＆＃34;：＆＃34; 34912＆＃34;＆＃34; L＆＃34;：空，＆＃34; NS＆＃34;：空，＆＃34;米＆＃34;：空，＆＃34; NULL＆＃34;：空，＆＃34; BOOL＆＃34;：空}}

之后我还要实现还原应用程序。谢谢

Answer 1

我用csv格式做了这个，看起来最简洁。第一行应该包含字段名称（有点像excel标题），因此它们不会重复每一行，而stil启用解析文件。空值只是相邻的逗号。

保存dynamoDB表的最佳文件格式是什么？

1 个答案: