Geronimo Config User Guide

19 September 2017

To get started with Geronimo Config, you’ll want to add the dependencies to the project. Eclipse MicroProfile Config is a transitive dependency, it will come in automatically as a dependency.

If you’re using Maven:

<dependency>
    <groupId>org.apache.geronimo.config</groupId>
    <artifactId>geronimo-config-impl</artifactId>
    <version>1.0</version>
</dependency>

If you’re using Gradle:

dependencies {
     compile 'org.apache.geronimo.config:geronimo-config-impl:1.0'
}

General Use Cases

Registering Config Sources

ConfigSource implementations can be registered via ServiceLoader. Declare a ServiceLoader of type ConfigSource or ConfigSourceProvider to register these classes.

Default Config Sources

By default, we register a ConfigSource for System Properties as well as Environment Variables.

Environment Variables are attempted using both . as well as _, meaning a property lookup for my.config.property will search both my.config.property as well as my_config_property, to conform to naming convention standards for environment variables.

System Properties are loaded on start up, copying the values into the config source instance. You can change this behavior by: - disabling default config source loading, and manually registering a SystemPropertyConfigSource passing in false in the constructor - Set the system property org.apache.geronimo.config.configsource.SystemPropertyConfigSource.copy to false

CDI Use Cases

Being an implementation of a MicroProfile specification, it favors use cases based on CDI. Most of the heavy lifting is done for you when using CDI.

Injecting Config

The MicroProfile Config interface is supported as an injection point. It is an @ApplicationScoped bean, loaded from the result of ConfigProvider.getConfig().

@Inject
private Config config

Will allow you to use the default Config object for your application. All of the operations of Config match the MicroProfile Specification.

Injecting Config Properties

Injecting @ConfigProperty works based on the specification.

In addition to the defined supported types, Geronimo Config supports injecting Supplier<T> where T is any type that has a supported Converter.

Non-CDI Use Cases

You may not be using CDI, or do not want to use the built in CDI integration. You can then using the programmatic look up for the configuration.

Config config = ConfigProviderResolver.instance().getBuilder()
    .addDefaultSources() // built in config sources (system properties, environment variables and microprofile-config.properties
    .addDiscoveredConverters() // converters discovered via ServiceLoader
    .addDiscoveredSources() // sources discovered via ServiceLoader
    .withConverters() // list of converter instances, cannot be lambda expressions
    .withSources() // list of config source instances
    .forClassLoader() // the classloader associated with this config
    .build()

This will register and build a Config object for use. You will need to keep track of that created instance. If you want it to be managed automatically, you can then register it

ConfigProviderResolver.instance().registerConfig(config, classLoader);