从多个 QuerySpec AWS Dynamodb 创建大型 JSON 响应

Question

我使用 QuerySpec 有多个查询，因此有多个 ItemCollection ：

            Table table4 = dynamoDB.getTable("MyTable"); 
            QuerySpec spec4 = new QuerySpec()
                    .withKeyConditionExpression("id = :v_id")
                    .withValueMap(new ValueMap()
                    .withString(":v_id", SAFETY_CHAPTERS_UUIDS.get(i)));
            ItemCollection<QueryOutcome> items4 = table4.query(spec4);
            Iterator<Item> iterator4 = items4.iterator();
            Item itemsQuizzChapters = null;

我正在尝试找到一种方法来从这 4 个查询中构建一个大的 JSON 响应。如何将itemCollection添加到JSON对象或对象，以便我可以使用所有这些对象创建一个大对象？

Answer 1

//import aws-java-sdk-bundle-1.11.85.jar, json-simple-1.1.jar and jackson-all-1.9.9.jar
public JSONObject getItemDynamoDB(String tableName, String primaryKey,String primaryKeyValue) {
       Table index = dynamoDB.getTable(tableName);
        QuerySpec querySpec = new QuerySpec().withKeyConditionExpression("#primaryKey = :value1")
        .withNameMap(new NameMap().with("#primaryKey", primaryKey))
        .withValueMap(new ValueMap().withString(":value1", primaryKeyValue));
        ItemCollection<QueryOutcome> items = index.query(querySpec);
       Iterator<Item> itemIterator = items.iterator();
        JSONObject jsonObject = null;
        try {
        Object obj = jsonParser.parse(itemIterator.next().toJSONPretty());
        jsonObject = (JSONObject) obj;
    } catch (ParseException e) {
        e.printStackTrace();
    }
        return jsonObject;
}
//call the function multiple time to get big JSON
public JSONArray concatenateMultipleItem(){
    JSONArray jsonArray = new JSONArray() ;
    jsonArray.add(getItemDynamoDB("TableName", "primaryKey", "1"));
    jsonArray.add(getItemDynamoDB("TableName2", "primaryKey2", "2"));   
    System.out.println(jsonArray);
    return jsonArray;
}

参考

Answer 2

下面是查询两个不同的表Movies和post并返回JSONObject列表的示例代码（即org.json.JSONObject）。

Item 类具有将项目数据作为 Json 字符串返回的toJSON()。toJSON() 方法可用于将物料数据存储为List<String>或List<JSONObject>。

在下面的代码示例中，我返回List<JSONObject> .

示例代码：-

List<JSONObject> resultJson = new ArrayList<>();
DynamoDB dynamoDB = new DynamoDB(dynamoDBClient);
Table tableMovies = dynamoDB.getTable("Movies");
QuerySpec querySpecMovies = new QuerySpec();
querySpecMovies.withKeyConditionExpression("yearkey = :yearval")
        .withValueMap(new ValueMap().withNumber(":yearval", 2014));
IteratorSupport<Item, QueryOutcome> iterator = tableMovies.query(querySpecMovies).iterator();
while (iterator.hasNext()) {
    Item movieItem = iterator.next();
    System.out.println("Movie data ====================>" + movieItem.toJSONPretty());                      
    resultJson.add(new JSONObject(movieItem.toJSON()));
}
Table tablePosts = dynamoDB.getTable("post");
QuerySpec querySpecPosts = new QuerySpec();
querySpecPosts.withKeyConditionExpression("postId = :postIdval")
        .withValueMap(new ValueMap().withString(":postIdval", "3"));
iterator = tablePosts.query(querySpecPosts).iterator();
while (iterator.hasNext()) {
    Item postItem = iterator.next();
    System.out.println("Post data ====================>" + postItem.toJSONPretty());                        
    resultJson.add(new JSONObject(postItem.toJSON()));
}
return resultJson;

输出：-

[{
    "country": ["IN", "UK", "US"],
    "Description": "Delete and set",
    "yearkey": 2014,
    "total_val": 0,
    "title": "The Big New Movie 2",
    "total_new_val": 2
}, {
    "postId": "3",
    "text": "Hello World",
    "tags": ["A", "C"]
}]