DynamoDB Composite PK with UUID

Question

I have an issue with UUID when it is used in my PK in DynamoDB in the format

PK :EXAMPLE#{someUUID}

I am generating a UUID using the @DynamoDBAutoGeneratedKey annotation in springboot which generates the UUID in my field but is however, not present in my PK.

My model implementation:

public class ExampleClass {
   
    @DynamoDBHashKey(attributeName = "PK")
    public String getPK() {
        return "EXAMPLE" + someUUID;
    }
    
    @DynamoDBAttribute
    @DynamoDBAutoGeneratedKey 
    private String someUUID;
}

My results when I insert a record using DynamoDBMapper.save inserts the records with all the attributes but with:

PK : EXAMPLE#null

Programmically creating the UUID before insert fixes the problem, however I have to generate the UUID manually before every insert which isn't ideal.

Is there any way to populate getPK() while using DynamoDBAutoGeneratedKey?

Answer 1

My implamatation for this context:

1º - Create one anotation:

package io.github.wesleyosantos91.api.anotation;

import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAutoGenerateStrategy;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAutoGenerated;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAutoGenerator;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.UUID;

@DynamoDBAutoGenerated(generator=CustomGeneratedKey.Generator.class)
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD})
public @interface CustomGeneratedKey {
    String prefix() default "";

    public static class Generator implements DynamoDBAutoGenerator<String> {
        private final String prefix;
        public Generator(final Class<String> targetType, final CustomGeneratedKey annotation) {
            this.prefix = annotation.prefix();
        }
        public Generator() {
            this.prefix = "";
        }
        @Override
        public DynamoDBAutoGenerateStrategy getGenerateStrategy() {
            return DynamoDBAutoGenerateStrategy.CREATE;
        }
        @Override
        public final String generate(final String currentValue) {
            return prefix + UUID.randomUUID();
        }
    }
}

2º - Add anotation in atribute with desired prefix:

@DynamoDBHashKey
@CustomGeneratedKey(prefix="PERSON#")
private String id;

Result

PERSON#43bcad81-7bad-4c5f-ad55-dc26ced3c3ef

Reference: https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBAutoGenerated.html