Java:使用 Mapper 查询 DynamoDB 表中 Range 键的所有值

Question

我有一个 DynamoDb 表。它的哈希键为“ID”，范围键为“Category”。

我正在尝试查找“类别”的所有条目，例如喜剧。

这是我的映射类:

@DynamoDBTable(tableName = "Videos")
public class VideoDynamoMappingAdapter {

    private String videoID;
    private String videoCategory;
    private String videoArtist;
    private String videoTitle;

    @DynamoDBHashKey(attributeName = "ID")
    public String getVideoID() {
        return videoID;
    }

    public void setVideoID(String videoID) {
        this.videoID = videoID;
    }
    @DynamoDBRangeKey(attributeName = "Category")
    public String getVideoCategory() {
        return videoCategory;
    }

    public void setVideoCategory(String videoCategory) {
        this.videoCategory = videoCategory;
    }

    @DynamoDBAttribute(attributeName = "ArtistName")
    public String getVideoArtist() {
        return videoArtist;
    }

    public void setVideoArtist(String videoArtist) {
        this.videoArtist = videoArtist;
    }

    @DynamoDBAttribute(attributeName = "VideoTitle")
    public String getVideoTitle() {
        return videoTitle;
    }

    public void setVideoTitle(String videoTitle) {
        this.videoTitle = videoTitle;
    }

}

我一直在尝试查询这样的内容:

    DynamoDBQueryExpression<VideoDynamoMappingAdapter> queryExpression = new DynamoDBQueryExpression<VideoDynamoMappingAdapter>()
            .withRangeKeyCondition()


    List<VideoDynamoMappingAdapter> itemList = mapper.query(VideoDynamoMappingAdapter.class, queryExpression);

我一直在查看指南，但我无法理解它，我本以为这将是一个一直在执行的简单查询，所以也许我遗漏了一些东西:

http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryingJavaDocumentAPI.html#DocumentAPIJavaQueryExample

预先感谢您的帮助

Answer 1

Notionquest 的回答是正确的，我无法在给定范围条件下查询哈希键的所有值。我通过在类别属性上创建全局二级索引解决了这个问题。

这是我的映射器类:

@ DynamoDBTable(tableName = "AlarmTable")
public class VideoDynamoMappingAdapter {

    private String videoID;
    private String videoCategory;
    private String videoArtist;
    private String videoTitle;

    @DynamoDBHashKey(attributeName = "ID")
    public String getVideoID() {
        return videoID;
    }

    public void setVideoID(String videoID) {
        this.videoID = videoID;
    }

    @DynamoDBIndexHashKey( globalSecondaryIndexName = "CategoryIndex", attributeName = "Category")
    public String getVideoCategory() {
        return videoCategory;
    }

    public void setVideoCategory(String videoCategory) {
        this.videoCategory = videoCategory;
    }

    @DynamoDBAttribute(attributeName = "VideoArtist")
    public String getVideoArtist() {
        return videoArtist;
    }

    public void setVideoArtist(String videoArtist) {
        this.videoArtist = videoArtist;
    }

    @DynamoDBAttribute(attributeName = "VideoTitle")
    public String getVideoTitle() {
        return videoTitle;
    }

    public void setVideoTitle(String videoTitle) {
        this.videoTitle = videoTitle;
    }

}

请注意类别上的注释。

然后我的查询是这样的:

VideoDynamoMappingAdapter videosToFind = new VideoDynamoMappingAdapter();
        videosToFind.setVideoCategory("Other");

        DynamoDBQueryExpression<VideoDynamoMappingAdapter> queryExpression = new DynamoDBQueryExpression<VideoDynamoMappingAdapter>()
                .withIndexName("CategoryIndex")
                .withHashKeyValues(videosToFind)
                .withConsistentRead(false);

        List<VideoDynamoMappingAdapter> itemList = mapper.query(VideoDynamoMappingAdapter.class, queryExpression);
        System.out.println("test" + itemList.size());

我希望它对某人有所帮助。