org.eclipse.microprofile.config.package-info Maven / Gradle / Ivy
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* Copyright (c) 2016-2018 Contributors to the Eclipse Foundation
*
* See the NOTICE file(s) distributed with this work for additional
* information regarding copyright ownership.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* You may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
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/**
* Configuration for Java MicroProfile
*
* Rationale
*
*
* For many project artifacts (e.g. WAR, EAR) it should be possible to build them only once and then install them at
* different customers, stages, etc. They need to target those different execution environments without the necessity of
* any repackaging. In other words: depending on the situation they need different configuration.
*
*
* This is easily achievable by having a set of default configuration values inside the project artifact. But be able to
* overwrite those default values from external.
*
*
How it works
*
*
* A Configuration consists of the information collected from the registered
* {@link org.eclipse.microprofile.config.spi.ConfigSource ConfigSources}. These {@code ConfigSources} get sorted
* according to their ordinal. That way it is possible to overwrite configuration with lower importance from
* outside.
*
*
* By default there are 3 ConfigSources:
*
*
* - {@code System.getProperties()} (ordinal=400)
* - {@code System.getenv()} (ordinal=300)
* - all {@code META-INF/microprofile-config.properties} files on the ClassPath. (ordinal=100, separately configurable
* via a config_ordinal property inside each file)
*
*
*
* That means that one can put the default configuration in a {@code META-INF/microprofile-config.properties} anywhere
* on the classpath and the Operations team can later simply e.g set a system property to change this default
* configuration.
*
*
* It is of course also possible to register own {@link org.eclipse.microprofile.config.spi.ConfigSource ConfigSources}.
* A {@code ConfigSource} could e.g. read configuration values from a database table, a remote server, etc
*
*
Accessing and Using the Configuration
*
*
* The configuration of an application is represented by an instance of {@link org.eclipse.microprofile.config.Config}.
* The {@link org.eclipse.microprofile.config.Config} can be accessed via the
* {@link org.eclipse.microprofile.config.ConfigProvider}.
*
*
* Config config = ConfigProvider.getConfig();
* String restUrl = config.getValue("myproject.some.endpoint.url", String.class);
*
*
*
* Injection via a JSR-330 DI container is also supported:
*
*
* @Inject
* @ConfigProperty(name="myproject.some.endpoint.url");
* private String restUrl;
*
*
* @author Emily Jiang
* @author Mark Struberg
*/
@org.osgi.annotation.versioning.Version("3.0.0")
package org.eclipse.microprofile.config;