Implementing a Custom Configuration Source

This guide shows how to create a custom ConfigurableValueSource to load dynamic variable values from sources other than HOCON files or DPS.

Overview

Custom configuration sources allow you to load dynamic variable values from:

  • Databases

  • Remote configuration services (Consul, etcd, AWS Parameter Store)

  • Environment variables

  • Custom file formats

  • Any other external source

Prerequisites

  • The ipf-studio-configuration-core dependency

  • Spring Boot application

  • Understanding of the ConfigurableValueSource interface

Steps

1. Add Core Dependency

<dependency>
    <groupId>com.iconsolutions.dsl.studio</groupId>
    <artifactId>ipf-studio-configuration-core</artifactId>
    <version>${ipf-studio-configuration.version}</version>
</dependency>

2. Implement ConfigurableValueSource

Create a class that implements the ConfigurableValueSource interface:

import com.iconsolutions.dsl.studio.configurablevalues.ConfigurableValue;
import com.iconsolutions.dsl.studio.configurablevalues.ConfigurableValueSource;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.stream.Collectors;

@Component
public class DatabaseConfigurableValueSource implements ConfigurableValueSource {

    private final DynamicConfigRepository repository;

    public DatabaseConfigurableValueSource(DynamicConfigRepository repository) {
        this.repository = repository;
    }

    @Override
    public String getName() {
        return "database";
    }

    @Override
    public Integer getPrecedence() {
        return 15;  // Higher than HOCON (5) and default dynamic settings (10)
    }

    @Override
    public List<ConfigurableValue> getValues() {
        return repository.findAll().stream()
            .map(entity -> new ConfigurableValue(
                entity.getKey(),
                entity.getValue()
            ))
            .collect(Collectors.toList());
    }
}

3. Understand Precedence

The precedence determines the order in which sources are processed. This is only applied at startup, once the application is running updates to the DynamicExpressionRegistry will be applied without considering the precedence levels. Higher values override lower values:

Source Precedence Effect

HOCON files

5

Processed first (base values)

Dynamic Settings

10

Can override HOCON

Your Custom Source

15

Overrides both above

Choose your precedence based on where your source fits in the override hierarchy.

Additional Resources