Store Java Enum's String Value Instead of Enum Value Itself in Dynamodb

You can code the Alert class like this i.e. define the attribute as String and design the getter and setter to send/receive enum object (i.e. Source).

Alert class:-

    @DynamoDBTable(tableName = "Alerts")
public final class Alert implements Serializable {
    private static final long serialVersionUID = 4012517315640518044L;

    private String alertId;

    private String type;

    @DynamoDBHashKey(attributeName = "AlertId") 
    public String getAlertId() {
        return alertId;
    }

    @DynamoDBAttribute(attributeName = "Source")
    public Source getType() {
      if (type != null)
        return Source.valueOf(type);
      else
        return null;
    }

    public void setAlertId(String alertId) {
        this.alertId = alertId;
    }

    public void setType(Source type) {
        this.type = type.desc();
    }
}

Create Alert:-

Stores the value as expected on database table. The get item from DynamoDB table also works fine.

public Boolean createAlert(String alertId, Source source) {
    DynamoDBMapper dynamoDBMapper = new DynamoDBMapper(dynamoDBClient);
    Alert alert = new Alert();
    alert.setAlertId(alertId);
    alert.setType(source);
    dynamoDBMapper.save(alert);

    return true;

}

Override toString() this should work.

public enum Source {

  BREACH("breach"),
  LEAKAGE("leakage");

  private final String desc;

  Source(String desc) { this.desc = desc; }

  public String desc() { return desc; }

  @Override
  public String toString() { return desc; }
}

I solved it by defining a custom attribute converter. It works but I'm afraid you'd have to write converters for each enum.

There is already method for serializing desc().We can define a static method for deserializing toSource() Source.java

public enum Source {
    BREACH("breach"),
    LEAKAGE("leakage");

    private final String desc;

    Source(String desc) {
        this.desc = desc;
    }

    public String desc() {
        return desc;
    }

    public static Source toSource(String value) {
        return Arrays.stream(Source.values()).filter(et -> et.desc().equals(value)).findFirst().orElse(null);
    }
}

We can then define a custom DynamoDBType converter:

SourceEnumDynamoDbConverter.java

public class SourceEnumDynamoDbConverter implements DynamoDBTypeConverter<String, Source> {
    @Override
    public String convert(Source source) {
        return source.desc();
    }

    @Override
    public Source unconvert(String sourceStr) {
        return Source.toSource(sourceStr);
    }
}

And finally annotate our Entity's Source property with this custom converter Alert.java

@DynamoDBTable(tableName = "Alerts")
public final class Alert implements Serializable {
    private static final long serialVersionUID = 4012517315640518044L;

    @DynamoDBHashKey(attributeName = "AlertId") // Partition Key or Hash Attribute
    private String alertId;

    private Source type;

    @DynamoDBTypeConverted(converter = TrialEnumDynamoDbConverter.class)
    @DynamoDBAttribute(attributeName = "Source")
    public Source getSource() {
        return type;
    }

    public void setSource(Source type) {
        this.type = type;
    }

    // Constructor(s), Getter(s), Setter(s), ToString, etc...
}

This way desc is stored and read from dynamodb resulting in

{
  "AlertId": { "S": "a083168d-cb23-4ec8-ab80-a1c16955c4b8" },
  "Source": { "S": "breach" },
  ...
  "CreatedAt": { "S": "2017-05-03T14:07:36.395Z" }
}