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YamlConfig

Build Package

Yaml is a data serialization format similar to JSON but more human readable. It looks better to organize config in a YAML file since it makes sense to maintain some properties in a hierarchical manner.

YamlConfig helps read configuration for a java project from a YAML config file and access them via dotted notation.

Features

  • Uses SnakeYAML for reading YAML, so it can handle any data recognizable by SnakeYAML.
  • Ease of access using dotted notation to read properties

Getting Started

The latest jar can be downloaded from the releases page.

If you use Maven for Dependency management, you can include this using below dependency.

<dependency>
  <groupId>com.github.jsixface</groupId>
  <artifactId>yamlconfig</artifactId>
  <version>1.2.0</version>
</dependency>

Or if you use Gradle, you can include this using below dependency.

implementation 'com.github.jsixface:yamlconfig:1.2.0'

Usage - internal Yaml

Get an instance of the YamlConfig by passing in a reader or an inputstream.

InputStream resource = getClass()
                         .getClassLoader()
                         .getResourceAsStream("config.yml");

YamlConfig config = YamlConfig.load(resource);

Assume the contents of config.yml is as below:

services:
  db:
    image: mysql
    container_name: mysql_db
  endpoint:
    - host: example.com
      port: 2976
    - host: example.com
      port: 2978

You can access the value of db image by:

String imgName = config.getString("services.db.image");

It can also be used to get through arrays like below:

String value = config.getString("services.endpoint[1].host");

Usage - externally supplied Yaml

As above, but with you supplying the Yaml instance, allowing Yaml to template environment variables to override yaml supplied values.

# externally managed and configured Yaml instance.
Yaml yaml = new Yaml(new EnvScalarConstructor());
yaml.addImplicitResolver(EnvScalarConstructor.ENV_TAG, EnvScalarConstructor.ENV_FORMAT, "$");

# externally managed yml file
InputStream resource = getClass()
                         .getClassLoader()
                         .getResourceAsStream("config.yml");
                         
# pass the lot to YamlConfig
YamlConfig config = YamlConfig.load(yaml, resource);

# and now you can use fully qualified dot notation keys:
config.getString("service.db.someKey");

allowing *.yml files to contain key: ${ENV_KEY:-defaultValue} like this:

services:
  db:
    someKey: ${SOME_KEY:-defaultValue}

see the test YamlConfigWithEnvOverridesTest.java and its config file: testWithEnvOverrides.yml