Config Loader

Each config loader understands how to load a specific type of config. Often this is associated with a specific ConfigSource. For example the EnvironmentVarsLoader only loads the EnvironmentConfigSource. However, some loaders expect a format of the config, but accept it from multiple sources. For example the PropertyLoader expects the typical java property file, but it can come from any source as long as it is an input stream. It may be the system properties, local file, github, or S3.

Config Loader	Formats supported	details	module
EnvironmentVarsLoader	envVars	Loads Environment Variables from the EnvironmentConfigSource, it expects a list not a InputStream. By default, it splits the paths using a "_". You can also disable failOnErrors if you are receiving errors from the environment variables, as you can not always control what is present. By treating Errors as warnings it will not fail if it finds a configuration the parser doesn't understand. Instead it will ignore the specific config.	core
MapConfigLoader	mapConfig	Loads a user provided Map from the MapConfigSource, it expects a list not a InputStream. By default, it splits the paths using a "." and tokenizes arrays with a numeric index as "[0]".	core
PropertyLoader	properties, props, and systemProperties	Loads a standard property file from an InputStream. By default, it splits the paths using a "." and tokenizes arrays with a numeric index as "[0]".	core
JsonLoader	json	Leverages Jackson to load json files and convert them into a ConfigNode tree.	gestalt-json
TomlLoader	toml	Leverages Jackson to load toml files and convert them into a ConfigNode tree.	gestalt-toml
YamlLoader	yml and yaml	Leverages Jackson to load yaml files and convert them into a ConfigNode tree.	gestalt-yaml
HoconLoader	config	Leverages com.typesafe:config to load hocon files, supports substitutions.	gestalt-hocon

If you didn't manually add any ConfigLoaders as part of the GestaltBuilder, it will add the defaults. The GestaltBuilder uses the service loader to create instances of the Config loaders. It will configure them by passing in the GestaltConfig to applyConfig. To register your own default ConfigLoaders add them to the builder, or add it to a file in META-INF\services\org.github.gestalt.config.loader.ConfigLoader and add the full path to your ConfigLoader

By default, Gestalt expects Environment Variables to be screaming snake case, but you can configure it to have a different case.

By registering a EnvironmentVarsLoaderModuleConfig with the GestaltBuilder you can customize the Environment Loader.

In this example it will expect double __ as delimiter.

 GestaltBuilder builder = new GestaltBuilder();
Gestalt gestalt = builder
  .addSource(EnvironmentConfigSourceBuilder.builder().build())
  .addModuleConfig(EnvironmentVarsLoaderModuleConfigBuilder
    .builder()
    .setLexer(new PathLexer("__"))
    .build())
  .build();

gestalt.loadConfigs();

You can also customize many of the Loaders such as the YamlLoader, TomlLoader, JsonLoader and HoconLoader by registering the Module Configs with the builder.

 GestaltBuilder builder = new GestaltBuilder();
Gestalt gestalt = builder
  .addSource(ClassPathConfigSourceBuilder.builder().setResource("/default.yaml").build())
  .addModuleConfig(YamlModuleConfigBuilder.builder()
    .setObjectMapper(customObjectmapper)
    .build())
  .build();

gestalt.loadConfigs();