如何将查询中的所有结果获取到 aws dynamodb 表？

Question

the first example given in http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryingJavaDocumentAPI.html which returns a ItemCollection

According to http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryAndScan.html#Pagination we need to get the lastevaluatedkey and perform the query again but there isn't any getlastevaluatedkey for a ItemCollection that is returned from dynamoDb.getTable("tableName").query(keyattribute)

Also ItemCollection documentation states that n/w calls would be made if iterated across page boundary so do we have to make calls till again as given in http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryAndScan.html#Pagination or not

Answer 1

getLastEvaluatedKey is a method of QueryResult (or ScanResult).

In the example you refer to, a collection of QueryOutcome is used, bypassing the QueryResult. To get the last evaluated key, you could try doing this

 QueryRequest request = new QueryRequest();
 request.setTableName(tablename);
 QueryResult result = dynamoDB.query(request);
 ItemCollection<QueryOutcome> items = result.getItems();
 Map<String,AttributeValue> lastKey = result.getLastEvaluatedKey();

I hope this helps.

Answer 2

Once you have the Map - you can further process the returned data. For example, in this example, the key name and data are pushed into two ArrayList objects:

 ArrayList<String> keys = new ArrayList<String>();
  ArrayList<String> keyVals = new ArrayList<String>();

  for (Map<String, AttributeValue> item : result.getItems()) {

        Set<String> key = item.keySet();
        Collection<AttributeValue> values = item.values();

       for (Iterator<String> it = key.iterator(); it.hasNext(); ) {
               String f = it.next();
                System.out.println(f);
               keys.add(f);
        }

        for (Iterator<AttributeValue> it2 = values.iterator(); it2.hasNext(); ) {
               AttributeValue v1 = it2.next();
               String yy= v1.getS();
               keyVals.add(yy);
             }
}

Then you can do what you need to do with the returned data