ph config

A multi-source configuration manager, that can use system properties, environment variables, resources and application specific values to work with.
See `ConfigFactory.getDefaultConfig ()` for the starting point. By default the following configurations sources are scanned in this order:
1. System properties – priority 400
1. Environment variables – priority 300
1. if the system property `config.resource` or the environment variable `CONFIG_RESOURCE` is present, and it points to an existing classpath resource, the first one matching is used – priority 200 or determined by the system property `config.resource.priority` or the environment variable `CONFIG_RESOURCE_PRIORITY`. Note: the file type is determined by the extension and defaults to “properties”.
1. if the system property `config.resources` (note the trailing “s”) or the environment variable `CONFIG_RESOURCES` is present, and it points to an existing classpath resource, all matching ones are used – priority 200 or determined by the system property `config.resources.priority` (also note the trailing “s”) or the environment variable `CONFIG_RESOURCES_PRIORITY`. Note: the file type is determined by the extension and defaults to “properties”.
1. if the system property `config.file` or the environment variable `CONFIG_FILE` is present, and it points to an existing file, it is used – priority 200 or determined by the system property `config.file.priority` or the environment variable `CONFIG_FILE_PRIORITY`. Note: the file type is determined by the extension and defaults to “properties”.
1. if the system property `config.url` or the environment variable `CONFIG_URL` is present, and it points to an existing URL, it is used – priority 200 or determined by the system property `config.url.priority` or the environment variable `CONFIG_URL_PRIORITY`. Note: the file type is determined by the extension and defaults to “properties”.
1. a JSON file called `private-application.json` – this is mainly to have an easy way to override settings – priority 195.
1. a properties file called `private-application.properties` – this is mainly to have an easy way to override settings – priority 190.
1. all JSON files called `application.json` that are in the classpath – priority 185.
1. all properties files called `application.properties` that are in the classpath – priority 180.
1. all properties files called `reference.properties` that are in the classpath – priority 1.

• Note: the default configuration does NOT contain any custom configuration files. It is solely based on system properties and environment variables.
• Note: JSON and Properties files are expected to be UTF-8
• Note: The usage of variables (as in `${xyz}`) to reference to other properties is currently not yet implemented

1. Variables

Since ph-config 10.2.0 the usage of variables in configuration properties can be enabled. By default the usage of variables is disabled for backwards compatibility reasons. To enable usage of variables, call `setReplaceVariables (true)` on your existing `Config` project.

Variables are represents in the form `${name}` where `name` is the name variable.
During the resolution of configuration values, `${name}` is replaced with the configuration item with the key `name`.
A configuration value can contain zero, one or more variables.
Configuration values with variables can reference other configuration values that also contain variables. Cyclic references between variables (e.g. `key1` references `key2` references `key3` references `key1` again) is detected and will lead to a non-resolution of variables in that particular value. Additionally a log message is emitted.

Example:

key1: value
key2: Also a ${key1}
key3: ${key2} but more ${key1}

Resolving `key2` will lead to the string `Also a value`.
Resolving `key3` will lead to the string `Also a value but more value`.

Note: To represent the dollar sign (`$`) in a configuration value mask it with a backslash (`\`) as in `\$`.
Note: In case a variable is referenced, that is not resolved the handling can be customized.

1. JSON format

The JSON configuration file must be a single large object so it must start with “{” and end with “}”.
The JSON syntax is a bit relaxed and allows for unquoted names (as in `key: “value”`) but other than that it is regular JSON.

1. Configuration property resolution

Each configuration property is trying to be resolved in all configured sources.
Each configured source is iterated in descending priority, so in the default setup stated above system properties would be searched first, then environment variables and then the optional available configuration files.

1. Maven usage

Add the following to your pom.xml to use this artifact:

<dependency>
  <groupId>com.helger.commons</groupId>
  <artifactId>ph-config</artifactId>
  <version>x.y.z</version>
</dependency>

Note: the Maven groupId changed in v10 from `com.helger` to `com.helger.commons`