DynamoDB 列表类型 [英] DynamoDB List type

问题描述

I have problems understanding how to create a List for dynamoDB from my Android app. I can store and load the { "deviceId": "920e185a-63ed-46ca-bfca-f7a484ccb708" } from my app. But then to add the List and store my JSON objects as Map in the List is were i struggle.

The dynamoDB structure I want to create and populate looks like this in a JSON format:

{ "data": [ { "heartBeatId": 1, "status": 1, "timeStamp": 1502183502711 }, { "heartBeatId": 2, "status": 1, "timeStamp": 1502183502812 } ], "deviceId": "90563daa-63ae-40c5-905e-9e8c02f9624f" } Then I want to populate the data List with the heartbeat object which is of Map type. { "heartBeatId": 2, "status": 1, "timeStamp": 1502183502812 } So im having problems defining the @DynamoDBTable(tableName = "heartbeat") class to create this structure.

I have been reading about the List and DynamoDBDocument here:

DynamoDBDocument

DataType List

This how the @DynamoDBTable(tableName = "heartbeat") class looks right now.

I hope someone can help me define it or give me clues on how to proceed getting the structure i need.

package com.example.android.awsdynamoapp;

import com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBAttribute;
import com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBDocument;
import com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBHashKey;
import com.amazonaws.mobileconnectors.dynamodbv2.dynamodbmapper.DynamoDBTable;

import java.lang.annotation.Annotation;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@DynamoDBTable(tableName = "heartbeat")
public class HeartBeat implements DynamoDBTable {

private String deviceId;
private Map<String, Integer> data;
private List dataList;

public HeartBeat(){};
public HeartBeat(String deviceId){this.deviceId = deviceId;};

public HeartBeat(String deviceId, List dataList) {
    this.deviceId = deviceId;
    this.dataList = dataList;
  //  this.timeStamp = timeStamp;
}

@DynamoDBHashKey(attributeName = "deviceId")
public String getDeviceId() {
    return deviceId;
}

public void setDeviceId(String deviceId) {
    this.deviceId = deviceId;
}
public void setTimeStamp(String timeStamp) {
    //this.timeStamp = timeStamp;
}


public void setData(String deviceId) {
    Map<String, Integer> data = new HashMap<>();

}

@DynamoDBAttribute(attributeName = "data")
public List getData() {
    return this.dataList;
}

@DynamoDBDocument
public static class JsonArray {
    private String heartBeatId;
    private String status;
    private String timeStamp;

}

/**
 * The name of the table to use for this class.
 */
@Override
public String tableName() {
    return "heartbeat";
}

@Override
public Class<? extends Annotation> annotationType() {
    return null;
}
}

解决方案

The list of map object can be created as follows. The good thing in the above structure is that all the attributes in data is a Number. You can change it to String if needed as well. Based on your expected output, I have defined it as Long.

Attribute Definition:-

private List<Map<String, Long>> data;

@DynamoDBAttribute(attributeName = "data")  
public List<Map<String, Long>> getData() {
    return data;
}

public void setData(List<Map<String, Long>> data) {
    this.data = data;
}

Populate the data:-

    MoviesWithData movies = new MoviesWithData();
    movies.setYearKey(1917);
    movies.setTitle("Tilte with list of map");

    Map<String, Long> dataMap1 = new HashMap<>();
    dataMap1.put("heartBeatId", 1L);
    dataMap1.put("status", 1L);
    dataMap1.put("timeStamp", 1502183502812L);

    Map<String, Long> dataMap2 = new HashMap<>();
    dataMap2.put("heartBeatId", 2L);
    dataMap2.put("status", 2L);
    dataMap2.put("timeStamp", 1503183502812L);

    movies.setData(Arrays.asList(dataMap1, dataMap2));
    dynamoDBMapper.save(movies, consistentDynamoDBMapperConfig);

Sample output:-

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