https://github.com/microbean/microbean-configuration-api

A Java library for defining the API for accessing configuration values, taking configuration coordinates into account.
https://github.com/microbean/microbean-configuration-api

configuration java java-library

Last synced: about 1 year ago
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A Java library for defining the API for accessing configuration values, taking configuration coordinates into account.

• Host: GitHub
• URL: https://github.com/microbean/microbean-configuration-api
• Owner: microbean
• License: apache-2.0
• Created: 2017-02-14T18:45:24.000Z (about 9 years ago)
• Default Branch: master
• Last Pushed: 2018-12-14T23:57:07.000Z (over 7 years ago)
• Last Synced: 2025-03-21T17:04:00.894Z (about 1 year ago)
• Topics: configuration, java, java-library
• Language: Java
• Homepage: https://microbean.github.io/microbean-configuration-api/
• Size: 653 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# microBean Configuration API

[![Build Status](https://travis-ci.org/microbean/microbean-configuration-api.svg?branch=master)](https://travis-ci.org/microbean/microbean-configuration-api)

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The microBean Configuration API project provides API classes and

interfaces for helping Java SE programs acquire configuration

information.

Unlike other configuration frameworks and APIs, the microBean

Configuration API is oriented around the concept of _configuration

coordinates_ within _configuration space_.

## Configuration Space

_Configuration space_ is defined as the unbounded universe of

configuration properties and their values, for all applications,

regardless of which system or systems might define or house them.

Dimensions within this space might include locale, region, data center

identifier, tenant identifier—these are only examples.  Of note

is that these are dimensions, not nodes within a hierarchy.  Many

configuration systems represent them as a hierarchy which makes

resolution of configuration ambiguities difficult.

## Configuration Coordinates

_Configuration coordinates_ are those which semantically locate an

application in configuration space.  So an application run in the US

locale, in the test environment, located in the Western region of a

cloud provider, in the Nevada data center and run on behalf of tenant

number 34 (to use the examples from the Configuration Space section

above) is located in configuration space with, perhaps, the following

logical configuration coordinates:

    locale=en_US

    environment=test

    region=west

    dataCenter=Nevada

    tenantId=34

    

While these coordinates look like configuration values themselves,

they are configuration values for locating the application in

configuration space, not (normally) the values that the application

will be looking up during the course of its execution.

## Configuration Properties

_Configuration properties_ are the names for which (non-hard-coded)

values are sought by an application.  `portNumber`,

`timeoutInSeconds`, `databaseUrl` and `userEmail` are arbitrary

examles of configuration properties.  These are, by definition,

non-specific identifiers.  They gain specificity only when further

pinpointed in configuration space by a set of configuration

coordinates.  That is, `databaseUrl` is a configuration property that

might have many different possible values for many different possible

applications.  The configuration property `databaseUrl` used by a

particular application is only relevant when it is interpreted in the

context of the appropriate set of configuration coordinates.  For

example, a configuration author may only be able to write a value for

the `databaseUrl` configuration property when she knows that the value

is supposed to be for the test environment in the Nevada data center

on behalf of tenant 34.  Or she may also be able to write a value for

the `databaseUrl` configuration property when she knows that the value

is supposed to be for the test environment and the Western region.  As

you can see, configuration coordinates are not hierarchical, and

neither (necessarily) are configuration properties.

## Configuration Values

_Configuration values_ are two things: the _values received by an

application_ situated in configuration space by its configuration

coordinates when that application asks for a value for a configuration

property, and _values that are written_ in such a way that they may be

found by one or more such applications.

For example, a configuration author might write a value, `red`, for a

hypothetical `color` configuration property, into a system somewhere,

once.  The author may decide (let's say) that this value is suited for

any application possessing any configuration coordinates.  In this

case, the value received by an instance of application _A_ identified

by one set of configuration coordinates, asking for a value for the

`color` configuration property will be the same as the value received

by another instance of _A_ identified by a different set of

configuration coordinates asking for a value for the `color`

configuration property.  The author thus wrote one configuration

value, but from the standpoint of the querying application instances,

there are two values in play.

## Configuration

A _configuration_ is simply a collection of some configuration

properties and their values designated for one or more

points—identified by configuration coordinates—in

configuration space.