Question

我试图通过服务向DynamoDB数据库添加多个条目，但是当执行代码时，只保存一个条目。这是我到目前为止所做的：

public int onStartCommand(Intent intent, int flags, int startId) {

    CognitoCachingCredentialsProvider credentialsProvider = new CognitoCachingCredentialsProvider(
            getApplicationContext(), // Context
            "us-east-1:851c121e-326d-4c9e-be47-fec40eb7b693", // Identity Pool ID
            Regions.US_EAST_1 // Region
    );

    AmazonDynamoDB client = new AmazonDynamoDBClient(credentialsProvider);

    Toast.makeText(this, "Adding To Database...", Toast.LENGTH_LONG).show();

    CognitoCachingCredentialsProvider cognitoProvider = new CognitoCachingCredentialsProvider(
            getApplicationContext(), // Context
            "us-east-1:851c121e-326d-4c9e-be47-fec40eb7b693", // Identity Pool ID
            Regions.US_EAST_1 // Region
    );

    AmazonDynamoDBClient ddbClient = new AmazonDynamoDBClient(cognitoProvider);

    DynamoDBMapper mapper = new DynamoDBMapper(ddbClient);

    String streamName = intent.getStringExtra("streamName");
    String userCreated = intent.getStringExtra("userCreated");
    ArrayList<String> selectedFriend = intent.getStringArrayListExtra("userInvolved");
    intent.getStringExtra("comment");

    for(int i = 0; i < selectedFriend.size(); i++){

        Streams streams = new Streams();

        streams.setStreamname(streamName);
        streams.setUsercreated(userCreated);
        streams.setUserinvolved(selectedFriend.get(i));
        streams.setUnread(true);
        streams.setDeleted(false);

        mapper.save(streams);

    }
}

就像我说的那样，只会保存一个条目。我被建议使用arraylist，但我不知道如何去做。有人可以帮忙吗？

感谢所有帮助。

编辑：Streams.java类：

@DynamoDBTable(tableName = "Streams")
public class Streams{

    private String streamname;
    private String usercreated;
    private String userinvolved;
    private boolean unread;
    private boolean deleted;

    @DynamoDBAttribute(attributeName = "Stream_Name")
    public String getStreamname() {
        return streamname;
    }

    public void setStreamname(String streamname) {
        this.streamname = streamname;
    }

    @DynamoDBHashKey(attributeName = "User_Created")
    public String getUsercreated() {
        return usercreated;
    }

    public void setUsercreated(String usercreated) {
        this.usercreated = usercreated;
    }

    @DynamoDBAttribute(attributeName = "User_Involved")
    public String getUserinvolved() {
        return userinvolved;
    }

    public void setUserinvolved(String userinvolved) {
        this.userinvolved = userinvolved;
    }

    @DynamoDBAttribute(attributeName = "Unread")
    public boolean isUnread() {
        return unread;
    }

    public void setUnread(boolean unread) {
        this.unread = unread;
    }

    @DynamoDBAttribute(attributeName = "Deleted")
    public boolean isDeleted() {
        return deleted;
    }

    public void setDeleted(boolean deleted) {
        this.deleted = deleted;
    }
}

Answer 1

您的DynamoDB哈希键似乎是Stream类中的user created字段。这是DynamoDB主键，它唯一标识DynamoDB表中的单个项目。

每次调用mapper.save(streams)时，您都会覆盖在循环的上一次迭代中编写的项目，因为您似乎只在此处设置了user created字段：

String userCreated = intent.getStringExtra("userCreated");。

尝试使用唯一标识符（例如stream name作为哈希键）。如果多个项具有相同的散列键，您还可以使用带有范围键的模式来创建（散列键，范围键）主键，以唯一标识DynamoDB表中的项。

Answer 2

DynamodbMapper有一个批量保存方法，允许您批量保存多个对象。查看DynamoDBMapper.batchSave。

无法将多个对象保存到DynamoDB？

2 个答案: