ConfigLib/docs/custom-config.md

This tutorial is intended to show how to add a custom configuration source. So, let's say you want to implement your own Configuration type, an InMemoryConfiguration, for example.

1. Extend Configuration

The first thing you have to do is to let your InMemoryConfiguration class extend Configuration<InMemoryConfiguration>.

import de.exlll.configlib.Configuration;
import de.exlll.configlib.ConfigurationSource;

public class InMemoryConfiguration extends Configuration<InMemoryConfiguration> {}

2. Create a ConfigurationSource

The second step is to create a class that implements ConfigurationSource<InMemoryConfiguration>.

final class InMemoryConfigurationSource
    implements ConfigurationSource<InMemoryConfiguration> {}

3. Implement save-/loadConfiguration

Next implement its methods.

final class InMemoryConfigurationSource
        implements ConfigurationSource<InMemoryConfiguration> {
    private Map<String, Object> configAsMap = new HashMap<>();

    /* The 'config' parameter is the Configuration instance that
     * requested the save/load */
    @Override
    public void saveConfiguration(
            InMemoryConfiguration config, Map<String, Object> map
    ) {
        this.configAsMap = map;
    }

    @Override
    public Map<String, Object> loadConfiguration(
            InMemoryConfiguration config
    ) {
        return configAsMap;
    }
}

4. Extend Properties and Builder

Within your InMemoryConfiguration class, create an InMemoryProperties class that extends Configuration.Properties. Within the InMemoryProperties class, create a Builder class that extends Properties.Builder.

public class InMemoryConfiguration extends Configuration<InMemoryConfiguration> {

    public static final class InMemoryProperties extends Properties {
        protected InMemoryProperties(Builder<?> builder) {
            super(builder);
        }

        public static Builder<?> builder() {
            return new Builder() {
                @Override
                protected Builder getThis() {
                    return this;
                }
            };
        }

        public static abstract class Builder<B extends Builder<B>>
                extends Properties.Builder<B> {
            public InMemoryProperties build() {
                return new InMemoryProperties(this);
            }
        }
    }
}

5. Add properties

Add properties to your InMemoryProperties class that can configure your InMemoryConfiguration in some meaningful way. For example:

public static final class InMemoryProperties extends Properties {
    private final int minMemory;
    private final int maxMemory;

    protected InMemoryProperties(Builder<?> builder) {
        super(builder);
        this.minMemory = builder.minMemory;
        this.maxMemory = builder.maxMemory;
    }

    public int getMinMemory() { return minMemory; }

    public int getMaxMemory() { return maxMemory; }

    public static Builder<?> builder() {
        return new Builder() {
            @Override protected Builder getThis() { return this; }
        };
    }

    public static abstract class Builder<B extends Builder<B>>
            extends Properties.Builder<B> {
        private int minMemory = 0;
        private int maxMemory = 1024;

        public B setMinMemory(int minMemory) {
            this.minMemory = minMemory;
            return getThis();
        }

        public B setMaxMemory(int maxMemory) {
            this.maxMemory = maxMemory;
            return getThis();
        }

        public InMemoryProperties build() {
            return new InMemoryProperties(this);
        }
    }
}

6. Implement getSource/getThis

The last step is to implement the getSource and getThis methods and override the constructor of your InMemoryConfiguration.

public class InMemoryConfiguration extends Configuration<InMemoryConfiguration> {
    private final InMemoryConfigurationSource source =
            new InMemoryConfigurationSource();

    protected InMemoryConfiguration(InMemoryProperties properties) {
        super(properties);
    }

    @Override
    protected ConfigurationSource<InMemoryConfiguration> getSource() {
        return source;
    }

    @Override
    protected InMemoryConfiguration getThis() {
        return this;
    }
}

7. Use your new InMemoryConfiguration

final class InMemoryDatabaseConfig extends InMemoryConfiguration {
    private final String host = "localhost";
    // ...

    public InMemoryDatabaseConfig(InMemoryProperties properties) {
        super(properties);
    }
    // ...

    public static void main(String[] args) {
        InMemoryProperties properties = InMemoryProperties.builder()
                .setMinMemory(123)
                .setMaxMemory(456)
                .build();

        InMemoryDatabaseConfig config = new InMemoryDatabaseConfig(properties);
        config.save();
    }
}