Question

我使用QuerySpec进行多次查询，从而使ItemCollection倍增：

            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;

我试图找到一种方法来构建来自这4个查询的大型JSON响应。我如何将itemCollection添加到JSON对象或对象，以便我可以用它创建一个大对象？

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;
}

here

Answer 2

以下是查询两个不同表Movies＆amp;的示例代码。 post并返回JSONObject列表（即org.json.JSONObject）。

Item类有一个toJSON()可以将项数据作为Json字符串返回。 toJSON()方法可用于将商品数据存储为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;

<强>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"]
}]

从多个QuerySpec AWS Dynamodb创建大型JSON响应

2 个答案: