Object Persistence Interface

Some AWS SDKs provide an object persistence interface where you do not directly perform data plane operations. Instead, you create objects that represent items in Amazon DynamoDB tables and indexes, and interact only with those objects. This allows you to write object-centric code, rather than database-centric code.

Note

Object persistence interfaces are available in the AWS SDKs for Java and .NET. For more information, see for DynamoDB.

The following Java program uses DynamoDBMapper, the object persistence interface of the AWS SDK for Java. The MusicItem class represents an item in the Music table.

package com.amazonaws.codesamples;

import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAttribute;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBHashKey;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBRangeKey;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTable;

@DynamoDBTable(tableName="Music")
public class MusicItem {
    private String artist;
    private String songTitle;
    private String albumTitle;
    private int year;

    @DynamoDBHashKey(attributeName="Artist")
    public String getArtist() { return artist;}
    public void setArtist(String artist) {this.artist = artist;}

    @DynamoDBRangeKey(attributeName="SongTitle")
    public String getSongTitle() { return songTitle;}
    public void setSongTitle(String songTitle) {this.songTitle = songTitle;}

    @DynamoDBAttribute(attributeName = "AlbumTitle")
    public String getAlbumTitle() { return albumTitle;}
    public void setAlbumTitle(String albumTitle) {this.albumTitle = albumTitle;}

    @DynamoDBAttribute(attributeName = "Year")
    public int getYear() { return year; }
    public void setYear(int year) { this.year = year; }
}

You can then instantiate a MusicItem object, and retrieve a song using the load() method of DynamoDBMapper. The program then prints the year that the song was released.

The com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper class implements the DynamoDB object persistence interface. Note how DynamoDBMapper acts as a wrapper around the low-level client (AmazonDynamoDB).

package com.amazonaws.codesamples;

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper;


public class MusicMapperDemo {

    public static void main(String[] args) {

        AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard().build();

        DynamoDBMapper mapper = new DynamoDBMapper(client);

        MusicItem keySchema = new MusicItem();
        keySchema.setArtist("No One You Know");
        keySchema.setSongTitle("Call Me Today");

        try {
            MusicItem result = mapper.load(keySchema);
            if (result != null) {
                System.out.println(
                "The song was released in "+ result.getYear());
            } else {
                System.out.println("No matching song was found");
            }
        } catch (Exception e) {
            System.err.println("Unable to retrieve data: ");
            System.err.println(e.getMessage());
        }

    }

}