Java中具有过滤器表达式的DynamoDb查询 [英] DynamoDb query with filter expression in Java

问题描述

我在AWS中有一个名为school-data的DynamoDb表。以下是使所有学校都具有学校名称的现有代码：

I have a DynamoDb table named school-data in AWS. Below is the existing code to get all the school with a school's name:

private DynamoDBQueryExpression<School> createQueryBySchoolName(String schoolName) {
    String matchSchoolName = "schoolName = :schoolName";
    Map<String, AttributeValue> schoolNames = new HashMap<>();
    schoolNames.put(":schoolName", new AttributeValue().withS(schoolName));

    return new DynamoDBQueryExpression<School>()
            .withIndexName("schoolName-index")
            .withKeyConditionExpression(matchSchoolName)
            .withExpressionAttributeValues(schoolNames)
            .withConsistentRead(false);
}

上面的查询工作正常。但是现在我需要获取所有具有特定学校名称和地址的学校。因此，表中的3列如下：

The above query works fine. But Now I need to fetch all schools with a particular school name and their address . So, below are the 3 columns in the table:

id   schoolName  details

详细信息列中的数据如下所示：

The data in details column looks like below:

{
"zone": "North",
"type": "Convent",
"address": {
    "id": "138",
    "street1": "123 Street",
    "street2": "456 Road"
}
}

因此，我需要提取所有名称为'ABC'并将street1命名为'123 Street'的学校。因此，我更新了以下查询，如下所示：

So, I need to fetch all the schools with name 'ABC' and address street1 as '123 Street'. So, I updated the above query as below:

private DynamoDBQueryExpression<School> createQueryBySchoolName(String schoolName) {
    String matchSchoolName = "schoolName = :schoolName";
    Map<String, AttributeValue> schoolNames = new HashMap<>();
    schoolNames.put(":schoolName", new AttributeValue().withS(schoolName));
    schoolNames.put(":streetName", new AttributeValue().withS("123 Street"));


    return new DynamoDBQueryExpression<School>()
            .withIndexName("schoolName-index")
            .withKeyConditionExpression(matchSchoolName)
            .withFilterExpression("details.address.street1 = :streetName")
            .withExpressionAttributeValues(schoolNames)
            .withConsistentRead(false);
}

但是，此操作不会返回任何数据。能否让我知道我在做什么错？

But, this returns no data. Can you please let me know what am I doing wrong?

推荐答案

您需要为DynamoDBQueryExpression设置HashKeyValues并添加页数限制

You need to set HashKeyValues for the DynamoDBQueryExpression and add the page limit

private DynamoDBQueryExpression<School> createQueryBySchoolName(String schoolName) {
String matchSchoolName = "schoolName = :schoolName";
Map<String, AttributeValue> schoolNames = new HashMap<>();
schoolNames.put(":schoolName", new AttributeValue().withS(schoolName));
schoolNames.put(":streetName", new AttributeValue().withS("123 Street"));


return new DynamoDBQueryExpression<Voucher>()
        .withHashKeyValues(schoolName)
        .withIndexName("schoolName-index")
        .withKeyConditionExpression(matchSchoolName)
        .withFilterExpression("details.address.street1 = :streetName")
        .withExpressionAttributeValues(schoolNames)
        .withConsistentRead(false)
        .withLimit(pPageSize);

}

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