Question

我只想在我添加的项目尚未存在的情况下添加属性。

据我所知，UpdateCondition构造只允许您根据项目的特定属性是否存在指定的值进行更新。

Answer 1

Here是执行条件看跌期权的帮助链接。

Help链接，用于使用条件放置仅放置属性（如果它不存在）。

已编辑：

如果不运行Amazon SimpleDB Query，则无法检查项目是否存在。您可以查询项目，如果amazon simpledb未在请求中返回该项目，则表示该项目不存在。检查示例代码 -

try {
            BasicAWSCredentials basicAWSCredentials = new BasicAWSCredentials("<accessKey>", "<secretkey>");
            AmazonSimpleDBClient amazonSimpleDBClient = new AmazonSimpleDBClient(basicAWSCredentials);
            amazonSimpleDBClient.setEndpoint("sdb.amazonaws.com");
            SelectRequest selectRequest = new SelectRequest("select * from `<domainName>` where itemName()='<itemName>'");
            SelectResult selectResult = amazonSimpleDBClient.select(selectRequest);
            List<Item> itemList = selectResult.getItems();
            if (itemList.size() == 0) {
                System.out.println("Specified item does not exist.");
                List<ReplaceableAttribute> list = new ArrayList<ReplaceableAttribute>();
                ReplaceableAttribute replaceableAttribute = new ReplaceableAttribute("<attribute>", "<value>", Boolean.TRUE);
                list.add(replaceableAttribute);
                PutAttributesRequest attributesRequest = new PutAttributesRequest("<domainName>", "<itemName>", list);
                amazonSimpleDBClient.putAttributes(attributesRequest);
            } else {
                System.out.println("Specified item exist. Do Nothing.");
            }
        } catch (Exception ex) {
            System.out.println(ex.toString());
        }

如果项目已存在，如何在SimpleDB中的项目中添加属性？

1 个答案: