Fallback

The io.smallrye.config.FallbackConfigSourceInterceptor allows to fall back to another configuration name, by providing a transformation function or just a simple key value map.

When a configuration name does not exist, there might be another configuration name that the config can fall back to provide the same expected behavior. The fallback function is only applied if the original resolved configuration name is not found and resolved to the fallback name.

package org.acme;

import java.util.function.Function;
import io.smallrye.config.FallbackConfigSourceInterceptor;

public class MicroProfileConfigFallbackInterceptor extends FallbackConfigSourceInterceptor {
    public MicroProfileConfigFallbackInterceptor(final Function<String, String> mapping) {
        super(name -> name.startsWith("microprofile.config") ?
                      name.replaceAll("microprofile\\.config", "smallrye.config") :
                      name);
    }
}

And registration in: META-INF/services/io.smallrye.config.ConfigSourceInterceptor

io.smallrye.config.MicroProfileConfigFallbackInterceptor

The MicroProfileConfigFallbackInterceptor can fallback configuration names in the microprofile.config namespace to the smallrye.config namespace.