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Posted to commits@tamaya.apache.org by an...@apache.org on 2014/12/17 00:26:33 UTC
[4/4] incubator-tamaya git commit: TAMAYA-29: Removed stage.
TAMAYA-19: Simplified environment model. -> Updated docs.
TAMAYA-29: Removed stage.
TAMAYA-19: Simplified environment model.
-> Updated docs.
Project: http://git-wip-us.apache.org/repos/asf/incubator-tamaya/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-tamaya/commit/cd513bf3
Tree: http://git-wip-us.apache.org/repos/asf/incubator-tamaya/tree/cd513bf3
Diff: http://git-wip-us.apache.org/repos/asf/incubator-tamaya/diff/cd513bf3
Branch: refs/heads/master
Commit: cd513bf36b7da240fef80b5660ff3399693b8954
Parents: 0b3b963
Author: anatole <an...@apache.org>
Authored: Wed Dec 17 00:26:20 2014 +0100
Committer: anatole <an...@apache.org>
Committed: Wed Dec 17 00:26:20 2014 +0100
----------------------------------------------------------------------
docs/Design.adoc | 117 ---
docs/design/0_UseCases.adoc | 319 -------
docs/design/1_Requirements.adoc | 50 --
docs/design/2_CoreConcepts.adoc | 843 ------------------
docs/design/3_Extensions.adoc | 841 ------------------
docs/design/4_ImplementationCore.adoc | 47 -
docs/pom.xml | 2 +-
.../main/asciidoc/PossibleContributions.adoc | 388 +++++++++
docs/src/main/asciidoc/design/0_UseCases.adoc | 319 +++++++
.../main/asciidoc/design/1_Requirements.adoc | 50 ++
.../main/asciidoc/design/2_CoreConcepts.adoc | 849 +++++++++++++++++++
docs/src/main/asciidoc/design/3_Extensions.adoc | 841 ++++++++++++++++++
.../asciidoc/design/4_ImplementationCore.adoc | 47 +
docs/src/main/asciidoc/design/Design.adoc | 117 +++
docs/tasks.adoc | 388 ---------
15 files changed, 2612 insertions(+), 2606 deletions(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/incubator-tamaya/blob/cd513bf3/docs/Design.adoc
----------------------------------------------------------------------
diff --git a/docs/Design.adoc b/docs/Design.adoc
deleted file mode 100644
index 403b4ff..0000000
--- a/docs/Design.adoc
+++ /dev/null
@@ -1,117 +0,0 @@
-Apache Tamaya -- Design Documentation
-=====================================
-:name: Tamaya
-:rootpackage: org.apache.tamaya
-:title: Apache Tamaya
-:revnumber: 0.1-SNAPSHOT
-:revremark: Incubator
-:revdate: November 2014
-:longversion: {revnumber} ({revremark}) {revdate}
-:authorinitials: ATR
-:author: Anatole Tresch, Anatole Tresch
-:email: <at...@gmail.com>
-:source-highlighter: coderay
-:website: http://tamaya.incubator.apache.org/
-:iconsdir: {imagesdir}/icons
-:toc:
-:toc-placement: manual
-:icons:
-:encoding: UTF-8
-:numbered:
-
-'''
-
-<<<
-
--> add image : : https://raw.githubusercontent.com/JavaConfig/config-api/master/src/main/asciidoc/images/javaconfig.jpg[]
-
-toc::[]
-
-<<<
-:numbered!:
------------------------------------------------------------
-Licensed to the Apache Software Foundation (ASF) under one
-or more contributor license agreements. See the NOTICE file
-distributed with this work for additional information
-regarding copyright ownership. The ASF licenses this file
-to you 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 limitations
-under the License.
------------------------------------------------------------
-
-:numbered:
-
-<<<
-
-== Introduction
-This document describes the {name} API for Configuration. The technical objective is to provide a
-unified configuration model in Java, targeting Java ME, SE as well as the EE platform.
-The API will provide support for key/value based application configuration. It will provide
-as well higher level APIs that are based on the low level ke</value pairs. Finally it will
-provide extension points for adding additional features and additional modules for extension
-or adaption.
-
-=== Working Group
-This work is being conducted as part of a community lead joint effort under the Apache Software Foundation. This
-specification is the result of the collaborative work of the members of the {name} Users Group and the community at
-large. Currently the project is lead by Anatole Tresch (atsticks at gmail.dot com).
-
-=== Goals
-Configuration is a key feature in all kind of programming languages. Basically configuration is the parametrization of
-well defined aspects of a software product without having to recompile/rebuild the code.
-
-==== Targets
-{name} targets to support all general configuration aspects, e.g.
-
-* spplication configuration
-** plugins
-** modules
-** components
-* Configuration of Java EE related aspects for Java enterprise application portability and dynamic provisioning, such as
-** Configuration of CDI (interceptors, decorators and alternatives)
-** Configuration of Bean Validation, JSF, web applications etc.
-* Configuration of instances within Java SE, e.g. by passing instances to a method that injects configured values, or by providing
- accessors to evaluate current configuration vlues. This can be used explicitly or transparently by client code.
-
-Additionally the solution should support
-
-* multiple configuration locations, including remote locations
-* multiple configuration formats, including custom formats
-* multiple configuration loading mechanisms, including custom mechanisms. By default reading the classpath, files und URIs are supported by default.
-* type conversion
-* configuration of collections
-
-
-=== Required Java version
-The API is based on Java SE 8.0 language features.
-
-=== How this document is organized
-There are five main section in this document:
-
-* Use cases.
-* Requirements.
-* Specification.
-* Implementation Recommendations.
-* An appendix.
-
-<<<
-include::design/0_UseCases.adoc[]
-
-<<<
-include::design/1_Requirements.adoc[]
-
-<<<
-include::design/2_CoreConcepts.adoc[]
-
-:numbered!:
-== APPENDIX
-
http://git-wip-us.apache.org/repos/asf/incubator-tamaya/blob/cd513bf3/docs/design/0_UseCases.adoc
----------------------------------------------------------------------
diff --git a/docs/design/0_UseCases.adoc b/docs/design/0_UseCases.adoc
deleted file mode 100644
index 8ec833e..0000000
--- a/docs/design/0_UseCases.adoc
+++ /dev/null
@@ -1,319 +0,0 @@
-// Licensed to the Apache Software Foundation (ASF) under one
-// or more contributor license agreements. See the NOTICE file
-// distributed with this work for additional information
-// regarding copyright ownership. The ASF licenses this file
-// to you 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 limitations
-// under the License.
-
-<<<
-[[UseCases]]
-== Use Cases
-
-This section describes some, but not all, of the use cases that should be covered by Tamaya.
-
-
-[[UCSimpleAccess]]
-=== Simple Property Access (UC 1)
-
-Tamaya should provide a simple Java API for accessing configuration. Hereby
-
-* Configuration is organized as key/value pairs. This basically can be modeled as +Map<String,String>+
-* Configuration should be as simple as possible. A +Map<String,String>+ instance has methods that may not
- be used in many use cases and/or are not easy to implement. Currently the following functionality
- must be supported:
- ** access a value by key (+get+)
- ** check if a value is present (+containsKey+)
- ** get a set of all defined keys (+keySet+)
- ** a property provider must be convertable to a +Map+, by calling +toMap()+
- ** a property provider must get access to its meta information.
-* The API must never return null.
-* The API should support undefined values.
-* The API must support passing default values, to be returned if a value is undefined.
-* The API must allow to throw exceptions, when a value is undefined.
- Customized exceptions hereby should be supported.
-* Properties can be stored in the classpath, on a file.
-* Properties can be stored in properties, xml-properties or ini-format.
-* Properties can also be provided as properties, or as a Map<String,String>
-
-
-[[UCAutoConfig]]
-=== Automatic Configuration
-
-* Tamaya should provide a feature for automatic configuration, where properties can be annotated.
-* Hereby the lifecycle of the instances configured should not be managed by Tamaya.
-* String as well as other types should be supported.
-* It should be possible to define default values to be used, if no valid value is present.
-* It should be possible to define dynamic expressions, at least for default values.
-* The values configured should be reinjected, if the underlying configuration changes.
-* Reinjection should be controllable by an injection policy.
-* It should be possible to evaluate multiple keys, e.g. current keys, and as a backup deprecated keys
- from former application releases.
-* The type conversion of the properties injected should be configurable.
-* The value evaluated for a property (before type conversion) may be adaptable as well.
-* It should be possible to observe configuration changes.
-
-The most simplest way is using injection, e.g. a POJO can be written as follows:
-
-[source, java]
-.Configured POJO Example
-----------------------------------------------------
-public class MyPojo {
- @ConfigProperty("myCurrency")
- @DefaultValue("CHF")
- private String currency;
-
- @ConfigProperty("myCurrencyRate")
- private Long currencyRate;
-}
-----------------------------------------------------
-
-The instance then can be passed for being configured:
-
-[source, java]
-.Configuring a POJO
-----------------------------------------------------
-MyPojo instance = new MyPojo();
-Configuration.configure(instance);
-----------------------------------------------------
-
-[[UCTemplates]]
-=== Configuration Templates
-
-For type safe configuration clients should be able to define an interface that is implemented by the
-configuration system:
-
-* clients define an interface and annotate it as required
-* the interface methods must not take any arguments
-* the configuration system can be called to return such an interface implementation.
-* the configuration system returns a proxy hereby providing the values required.
-* similar to configured types also templates support multiple values and custom adapters.
-* It is possible to listen on configuration changes for templates, so users of the templates
- may react on configuration changes.
-
-A template hereby is modelled by annotating an interface with the same annotations as for
-configured classes:
-
-[source, java]
-.Type Safe Configuration Template Example
-----------------------------------------------------
-public interface MyConfig {
- @ConfiguredProperty("myCurrency")
- @DefaultValue("CHF")
- String getCurrency();
-
- @ConfiguredProperty("myCurrencyRate")
- Long getCurrencyRate();
-
-}
-----------------------------------------------------
-
-The configuration system will then provide the interface as follows:
-
-[source, java]
-.Accessing a type safe Configuration Template
-----------------------------------------------------
-MyConfig config = Configuration.of(MyConfig.class);
-----------------------------------------------------
-
-Finally a +Configuration+ itself can be accessed as template as well, which
-provides full access to all features:
-
-[source, java]
-.Accessing a Configuration
-----------------------------------------------------
-Configuration config = Configuration.of(Configuration.class);
-----------------------------------------------------
-
-
-[[UCSimpleConfiguration]]
-=== Simple Property Based Configuration
-
-In this most simple usage scenario an application is configured by some property files contained in the
-Java archive.
-
-* It provides default property files in the formats defined by the JDK within its application archive.
-* It allows to override settings by system properties.
-* It is able to consider command line arguments as well.
-
-
-[[UCAdvancedPropertyBasedConfiguration]]
-=== Advanced Property Based Configuration
-
-Enhancing the previous scenario, we might as well consider the current environment. Saying that our overriding mechanisms
-must be improved, since
-
-* some environment settings should not be overridable
-* some defaults should be overridden by environment or system properties, whereas others may not
-* Additionally the user may have an option, where he is allowed to define an external configuration file that should be used to configure
- the application. This is especially useful for applications with lots of command line options (under windows even command
- execution may fail die to exceeding command length).
-* Finally application developers may have their own formats in place, so the system should be able to support these formats.
-
-
-[[UCModularizedConfiguration]]
-=== Modularized Configuration
-
-When systems grow they must be modularized to keep control. Whereas that sounds not really fancy, it leads to additional aspects
-to be considered by a configuration system.
-
-* Different code modules want to have their own "module configuration".
-* Some modules require a certain subset of keys to be read at once into a Map.
-* Products contain multiple modules, which per product are configured separately.
-
-
-[[UCTypeSupport]]
-=== Extended Type Support
-
-Application configuration must also support non String types such as primitives, wrapper types, math types
-and date/time values. Basically each type that can be created from a String in more standardized way should
-supported. This should be even possible for types not known at build time of possible. Type conversion hereby
-should be flexible.
-
-[[UCDynamicProvisioning]]
-=== Dynamic Provisioning
-
-In Cloud Computing, especially the PaaS and SaaS areas a typical use case would be that an application (or server)
-is deployed, configured and started dynamically. Typically things are controlled by some "active controller components",
-which are capable of
-* creating new nodes (using IaaS services)
-* deploying and starting the required runtime platform , e.g. as part of a PaaS solution.
-* deploying and starting the application modules.
-
-All these steps require some kind of configuration. As of today required files are often created on the target node
-before the systems are started, using proprietary formats and mechanism. Similarly accessing the configuration in place
-may require examining the file system or using again proprietary management functions. Of course, a configuration
-solution should not try to solve that, but it can provide a significant bunch of functionality useful in such scenarios:
-
-* provide remote capabilities for configuration
-* allow configuration to be updated remotely.
-* allow client code to listen for configuration changes and react as needed.
-
-Consequently:
-
--> Ensure Configuration can be transferred over the network easily.
-
--> Whereas many people will no think serializability is the solution, it would be much more useful to define
- a text based format for serialization, e.g. in +XML+ or +JSON+.
-
--> Similarly a management API should be defined, which allows to inspect the configuration in place, e.g. using
- JMX or REST services.
-
-[[UCJavaEE]]
-=== Java EE
-
-Considering Java EE different aspects should be considered:
-
-* Java EE is a complex multi-layered architecture with different levels of runtime contexts:
-** application server boot level (system classloader),
-** (optional) deployment/undeployment of ears (ear classloader),
-** (optional) deployment/undeployment of web applications (war classloader),
-** different runtime setups, e.g. EJB calls, MDB execution, Servlet Requests, scheduled and timed executions.
-* Configuring administrative resources (e.g. datasources, users, security etc) is typically vendor specific.
-* The environment is inherently multi-threaded.
-
-Given that a couple of additional requirements araise:
-
--> Configuration must be contextual, depending on the current runtime context (e.g. boot level, ear, war, ...).
-
--> Hereby contextual aspects can even exceed the levels described above, e.g. for SaaS scenarios.
-
--> Resources can be unloaded, e.g. wars, ears can be restarted.
-
--> The different contextual levels can also be used for overriding, e.g. application specific configuration
-may override ear or system configuration.
-
--> Configuration may be read from different sources (different classloaders, files, databases, remote locations).
-
--> Configuration may be read in different formats (deployment descriptors, +ServiceLoader+ configuration, alt-DD feature, ...)
-
--> JSF also knows the concept of stages.
-
--> Many SPI's of Java EE require the implementation of some well defined Java interface, so it would be useful if the
- configuration solution supports easy implementation of such instances.
-
--> In general it would be useful to model the +Environment+ explicitly.
-
--> Configuration used as preferences is writable as well. This requires mutability to be modelled in way, without the
- need of synchronization.
-
--> JNDI can be used for configuration as well.
-
-[[UCMultiTenancy]]
-=== Scenario MultiTenancy
-In multi tenancy setups a hierarchical/graph model of contexts for configurations is required. For example there might
-be some kind of layering as follows:
-
-* Layer 0: Low level system configuration
-* Layer 1: Domain configuration
-* Layer 2: Default App configuration
-* Layer 3: Tenant specific configuration
-* Layer 4: User specific configuration
-
-Configurations made in the tenant or user layer override the default app configuration etc.
-
--> It must be possible to structure Configuration in layers that can override/extend each other.
-
--> The current environment must be capable of mapping tenant, user and other aspects, so a corresponding configuration
- (or layer) can be derived.
-
-[[UCJavaAPI]]
-=== Accessing Configuration
-
-So far we described much how configuration must be organized and managed, but we got not concrete, how it is accessed.
-Basically there are two basic scenarios to be distinguished, which mainly depend on the way how the lifecycle of a component
-to be configured is managed:
-
-* If the lifecycle is managed manually by the developer, the configuration system
-** can inject configuration values, when explicitly called to to so
-** can provide an accessor for configuration.
-* If the lifecycle is managed by some container such as a DI container, the configuration
- system should leverage the functionality of the container, where possible.
-
-
-
-
-[[UCTesting]]
-=== Testing
-When testing a Java solution, it must be possible to easily control the configuration provided, so isolated
-component tests can be written effectively. Also it should be possible to control/isolate the configuration level for
-each test case.
-
--> isolation of configuration services is required
-
--> API for controlling the configuration provided, required for according implementations in the testing frameworks.
-
-[[UCStaging]]
-=== Staging
-Different companies go through different staging levels during the development of software components. Currently only
-rarely the EE frameworks support staging aspects, nevertheless no broader, well modelled staging concept is defined.
-Different companies also have different staging or sub-staging levels in place, which also must be reflected.
-Especially with sub-stages inheritance of stage related configuration is common sense and should be supported.
-
--> Main stages available and to be supported must be defined.
-
--> Enable additional stages to be added, so also custom stages can be supported.
-
-
-[[UCCotsIntegration]]
-=== Custom of the Shelf (COTS) Integration
-When buying software from an external software company it is often very cumbersome to integrate, adapt and customize
-third party software to the internal operational requirements. Especially, when software is delivered as ear modules
-portability is often very difficult and time consuming. Configuration should enable COTS providers to define a
-customization contract, which also can be part of the COTS software interface and integration specifications. This
-would allow operations to better control and configure third party solutions as possible, whereas in the evaluation
-phase the integration and configuration options can explicitly be defined.
-
--> It must be possible to document configuration aspects supported.
-
--> Configuration must be overridable from external sources (the operations which must operate the COTS solution).
-
http://git-wip-us.apache.org/repos/asf/incubator-tamaya/blob/cd513bf3/docs/design/1_Requirements.adoc
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diff --git a/docs/design/1_Requirements.adoc b/docs/design/1_Requirements.adoc
deleted file mode 100644
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--- a/docs/design/1_Requirements.adoc
+++ /dev/null
@@ -1,50 +0,0 @@
-// Licensed to the Apache Software Foundation (ASF) under one
-// or more contributor license agreements. See the NOTICE file
-// distributed with this work for additional information
-// regarding copyright ownership. The ASF licenses this file
-// to you 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 limitations
-// under the License.
-
-<<<
-[[Requirements]]
-== Requirements
-=== Core Configuration Requirements
-Based on the scope and use cases described above the following core requirements can be identified:
-
-* Configuration is modelled as String based key/value pairs.
-* Configuration can be combined using the GoF composite pattern. Hereby different composition policies can be applied, such as
- ** override: subsequent entries override existing ones.
- ** substraction: keys present in the second configuration will be removed.
- ** union-resolve: key/values were added, in case of conflicts a +ConfigException+ must be thrown.
- ** union-ignore: similar to union, whereas duplicates are ignored (leaving the initial value loaded).
- ** intersection:
-
-[[RequirementsServer]]
-=== Server Configuration Requirements
-shskjdhskhds sdkj ksjdks skjdskjd:
-
-. Req1
-. Req2
-
-[[RequirementsExtensions]]
-=== Extensions Requirements
-shskjdhskhds sdkj ksjdks skjdskjd:
-
-. Req1
-. Req2
-
-[[RequirementsNonFunctional]]
-=== Non Functional Requirements
-. Req1
-. Req2
-
http://git-wip-us.apache.org/repos/asf/incubator-tamaya/blob/cd513bf3/docs/design/2_CoreConcepts.adoc
----------------------------------------------------------------------
diff --git a/docs/design/2_CoreConcepts.adoc b/docs/design/2_CoreConcepts.adoc
deleted file mode 100644
index 41c2311..0000000
--- a/docs/design/2_CoreConcepts.adoc
+++ /dev/null
@@ -1,843 +0,0 @@
-// Licensed to the Apache Software Foundation (ASF) under one
-// or more contributor license agreements. See the NOTICE file
-// distributed with this work for additional information
-// regarding copyright ownership. The ASF licenses this file
-// to you 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 limitations
-// under the License.
-<<<
-[[CoreConcepts]]
-== {name} Core Concepts
-Though {name} is a very powerful and flexible solution there are basically only a few simple core concepts required that build
-the base of all the other mechanisms:
-
-The API contains the following core concepts/artifacts:
-
-* Literal Key/Value Pairs
-* _PropertySource:_ is the the SPI for a source that provides configuration data. A +PropertySource+
- hereby defines
- ** a minimalistic SPI to be implemented by the config data source
- ** provides data key/value pairs in raw format as String key/values only
- ** providers should not have any dependencies other than to the datasource
- ** providers may read context dependent data, but basically providers themselves are not contextual.
- Context management should be done by the ConfigurationProvider implementation that also is responsible
- for combining a set of property providers to a Configuration.
- _Configuration_ is the API that users of Tamaya will see, when they access configuration in raw format. Hereby +Configuration+
- ** adds type support for non String types
- ** provides functional extension points (+with,query+)
- ** allows registering/deregistering of change listeners
- ** is the entry point for evaluating the current +Configuration+
- ** each +PropertySource+ can be easily converted into a +Configuration+
- ** allows configuration entries to be injected
- ** to access configuration _templates_ (annotated interfaces).
- ** Configuration may support mutability by allowing instances of +ConfigChangeSet+ to be passed.
-* _PropertySourceBuilder_ allows to aggregate different property sources. Hereby property sources are
- seen as sets, which can be combined to new sources using set styled operations (aggregation, intersection, subtraction).
- This allows to model and create composite sources, to build up more complex configuration models
- step by step.
-* _MetaInfo_ is provided by each +Configuration, PropertySource+ and describes the configuration/provider and its entries.
-* _Environment_ is the base model for modelling the environment and the accessor for getting the current +Environment+ instance.
-* _Annotations_ a set of annotations allows to configure configuration injection on classes or interface (aka config templates).
-
-The SPI contains the following core concepts/artifacts:
-
-* _ServiceContext_ is the delegate singleton that is used by the framework to resolve components. The effective component
- loading can be accessed by implementing and registering an instance of +ServiceContextProvider+ using +java.util.ServiceLoader+.
-* All the singleton used explicitly (+PropertyAdapters,Configuration+ are backed up corresponding API interfaces.
- To override a singleton's behaviour the corresponding SPI has to be implemented and registered, so it can be loaded
- by the current +ServiceContext+ setup (by default ServiceLoader based).
-* Also the singleton used implicitly by +Configuration, Environment+ are backed up corresponding SPI interfaces.
- To override a singleton's behaviour the corresponding SPI has to be implemented and registered, so it can be loaded
- by the current +ServiceContext+ setup (by default ServiceLoader based).
-
-This is also reflected in the main parts of the API, which is quite small:
-
-* +org.apache.tamaya+ contains the main abstractions +Configuration, ConfigQuery, PropertyAdapter, Stage,
- Environment, PropertySource, MetaInfo+
-* +org.apache.tamaya.spi+ contains the SPI interfaces to be implemented by implementations and the +ServiceContext+ mechanism.
-+ +org.apache.tamaya.annot+ contains the annotations defined.
-
-In the implementation are there are additional projects:
-
-* +org.apache.tamaya.core+ contains the core implementation of the API. Deploying it together with the API results in a
- flexible framework that can be easily used for configuration of different complexity. But out of the box this framework
- will not do much more than exposing system and environment properties, its power comes when an additional meta-model
- is defined and deployed. Hereby you can write your own, or use on e of the provided ones (see later).
-* the core part is extended by multiple additional modules
- ** CDI integration
- ** Default configuration meta-models and providers for the most common usage scenarios
- *** standalone applications
- *** Java EE
- *** ...
-
-These parts are explained in the following sections. It is recommended that user's of the API read through this part.
-All subsequent parts are building upon this concepts and may be more difficult to understand without having read
-this section.
-
-
-[[APIKeyValues]]
-=== Key/Value Pairs
-
-Basically configuration is a very generic concept. Therefore it should be modelled in a generic way. The most simple
-and similarly most commonly used are simple literal key/value pairs. So the core building block of {name} are key/value pairs.
-You can think of a common +.properties+ file, e.g.
-
-[source,properties]
-.A simple properties file
---------------------------------------------
-a.b.c=cVal
-a.b.c.1=cVal1
-a.b.c.2=cVal2
-a=aVal
-a.b=abVal
-a.b2=abVal
---------------------------------------------
-
-Now you can use +java.util.Properties+ to read this file and access the corresponding properties, e.g.
-
-[source,properties]
-.Accessing some properties
---------------------------------------------
-Properties props = new Properties();
-props.readProperties(...);
-String val = props.getProperty("a.b.c");
-val = props.getProperty("a.b.c.1");
-...
---------------------------------------------
-
-This looks familiar to most of you. Nevertheless when looking closer to the above key/value pairs,
-there are more concepts in place: looking at the keys +a.b.c+, +a.b.c.1+, +a.b.c.2+, +a+, +a.b+ we
-see that the key names build up a flattened tree structure. So we can define the following:
-
-Given a key +p1.p2.p3.k=value+:
-
-* +p1.p2.p3.k+ is called the _qualified key_
-* +p1.p2.p3+ is the key's _area_
-* the child areas +p1.p2", "p1+ are called _areas_ as well
-* +k+ is the _(unqualified) key_
-
-Given that you can perform some very useful actions:
-
-* you can filter the keys with an area. E.g. in the example before you can query for all keys within the area +a.b.c+
- and map them to new properties set as follows:
-
-[source,properties]
-.Accessing an area
---------------------------------------------
-1=cVal1
-2=cVal2
---------------------------------------------
-
-Similarly accessing the area +a+ results in the following properties:
-
-[source,properties]
-.Accessing the area +a+
---------------------------------------------
-b=abVal
-b2=abVal
---------------------------------------------
-
-Additionally you can access all values of an area recursively, so accessing +a+ recursively results in
-the following properties:
-
-[source,properties]
-.Accessing area +a+ recursively
---------------------------------------------
-b.c=cVal
-b.c.1=cVal1
-b.c.2=cVal2
-b=abVal
-b2=abVal
---------------------------------------------
-
-Why this is useful? Well there are different use cases:
-
-* you can segregate your configuration properties, e.g. a module can access its module configuration by
- querying all properties under the area +config.modules.myModule+ (or whatever would be appropriate).
-* you can use this mechanism to configure maps (or more generally: collections).
-* you can easily filter parts of configuration
-* ...and more.
-
-==== Why Using Strings Only
-
-Using Strings as base representation of configuration comes with several huge advantages:
-
-* Strings are simple to understand
-* Strings are human readable and therefore easy to prove for correctness
-* Strings can easily be used within different language, different VMs, files or network communications.
-* Strings can easily be compared and manipulated
-* Strings can easily be searched, indexed and cached
-* It is very easy to provide Strings as configuration, which gives much flexibility for providing configuration in
- production as well in testing.
-* and more
-
-On the other side there are also disadvantages:
-
-* Strings are inherently not type safe, they do not provide validation out of the box for special types, such as
-numbers,
- dates etc.
-* Often you want not to work with Strings, but with according types.
-* Strings are not hierarchical, so mapping hierarchical structures requires some extra efforts.
-
-Nevertheless most of these advantages can be mitigated easily, hereby still keeping all the benefits from above:
-
-* Adding type safe converters on top of String allow to add any type easily, that can be directly mapped out of Strings.
- This includes all common base types such as numbers, dates, time, but also timezones, formatting patterns and more.
-* Even more complex mappings can be easily realized, by using String not as a direct representation of configuration,
- but a reference that defines where the more complex configuration artifact is available. This mechanism is similarly
- easy to understand as parsing Strings to numbers, but is powerful enough to provide e.g. all kind of deployment
- descriptors in Java EE.
-* Hierarchical and collection types can be mapped in different ways:
-** The keys of configuration can have additional syntax/semantics. E.g. when adding dor-separating path semantics
-*** trees/maps can also simply be mapped.
-
-[APIPropertySources]
-=== PropertySource
-==== Basic Model
-
-We have seen that constrain configuration aspects to simple literal key/value pairs provides us with an easy to
-understand, generic, flexible, yet expendable mechanism. Looking at the Java language features a +java.util.Map<String,
-String>+ and +java.util.Properties+ basically model these quite well out of the box.
-So it would make sense to build configuration on top of the JDK's +Map+ interface. This creates immediately additional
-benefits:
-
-* we inherit full Lambda and collection support
-* Maps are widely known and well understood
-
-Nevertheless there are some severe drawbacks:
-
-* Configuration also requires meta-data, such as
-** the origin of a certain configuration entry and how it was derived from other values
-** the sensitivity of some data
-** the provider that have read the data
-** the time, when the data was read
-** the timestamp, when some data may be outdated
-** ...
-
-Basically the same is also the not related to some single configuration key, but also to a whole map.
-The +PropertySource+ interface models exact these aspects and looks as illustrated below:
-
-[source,java]
-.Interface PropertySource
---------------------------------------------
-public interface PropertySource{
-
- Optional<String> get(String key);
- boolean containsKey(String key);
- Map<String, String> toMap();
- MetaInfo getMetaInfo();
-
- default Set<String> keySet();
- default ConfigChangeSet load();
- default boolean isMutable();
- default void apply(ConfigChangeSet change);
-}
---------------------------------------------
-
-Hereby
-
-* +getMetaInfo()+ return the meta information for the property provider, as well as for individual property key/value pairs.
-* +get+ look similar to the methods on +Map+, though +get+ uses the +Optional+ type introduced
- with Java 8. This avoids returning +null+ or throwing exceptions in case no such entry is available and also
- reduced the API's footprint, since default values can be easily implemented by calling +Optional.orElse+.
-* +containsKey, keySet+ are as well methods similar to +java.util.Map+ though implementations may only returns
- limited data, especially when the underlying map storage does not support iteration.
-* +isMutable()+ allows to easy check, if a property provider is mutable, which is more elegant than catching
- +NonSupportedOperation+ exception thrown on the according methods of +Map+.
-* +load()+ finally allows to (re)load a property map. It depends on the implementing source, if this operation
- has any effect. If the map changes an according +ConfigChange+ must be returned, describing the
- changes applied.
-* +toMap+ allows to extract thing to a +Map+. Similar to +containsKey, keySet+ implementations may only return
- a limited data map, especially when the underlying map storage does not support iteration.
-
-This simple model will be used within the spi, where configuration can be injected/provided from external resources.
-But we have seen, that we have to consider additional aspects, such as extendability and type safety. Therefore we
-extend +PropertySource+ and hereby also apply the 'composite pattern', which results in the following key abstraction.
-
-==== Meta Information
-
-Each instance also provides an instance of +MetaInfo+, which provides meta information for the providers and its properties:
-
-[source,java]
-.Accessing Meta Information
---------------------------------------------
-PropertySource prov = ...;
-MetaInfo metaInfo = prov.getMetaInfo();
-Set<String> keys = metaInfo.keySet(); // returns the attribute keys, for which meta-information is accessible.
-String metaData = metaInfo.get("a.b.c.value"); // access meta information
-String itemName = metaInfo.getName(); // access meta information for the provider
---------------------------------------------
-
-As we have seen above there is as well a +MetaInfoBuilder+, which must be used to create instances of
-+MetaInfo+.
-
-==== Mutability
-
-Property sources optionally may be mutable. This can be checked by calling +boolean isMutable()+. If a source
-is mutable a +ConfigChangeSet+ can be passed. This change set can then be applied by the source. On creation
-of the +ConfigChangeSetBuilder+ a source can pass version information, so _optimistic locking_ can be implemented
-easily:
-
-[source,java]
-.Creating and applying a +ConfigChangeSet+ to a PropertySource
---------------------------------------------
-PropertySource source = ...;
-ConfigChangeSet changeSet = ConfigChangeSetBuilder.of(provider) // creating a default version
- .remove("key1ToBeRemoved", +key2ToBeRemoved")
- .put("key2", "key2Value")
- .put("key3", 12345)
- .put("key4", 123.45)
- .build();
-source.apply(changeSet);
---------------------------------------------
-
-[[API PropertySourceBuilder]]
-==== Building Property Sources
-
-Looking at the structures of configuration system used by large companies we typically encounter some kind of configuration
-hierarchies that are combined in arbitrary ways. Users of the systems are typically not aware of the complexities in this
-area, since they simply know the possible locations, formats and the overriding policies. Framework providers on the other
-side must face the complexities and it would be very useful if Tamaya can support here by providing prebuilt functionality
-that helps implementing these aspects. All this leads to the feature set of combining property sources. Hereby the following
-strategies are useful:
-
-* aggregating providers, hereby later providers added
- ** override any existing entries from earlier providers
- ** combine conflicting entries from earlier providers, e.g. into a comma-separated structure.
- ** may throw a ConfigExcepotion ig entries are conflicting
- ** may only add entries not yet defined by former providers, preventing entries that are already present to be overwritte
- ** any custom aggregation strategy, which may be a mix of above
-* intersecting providers
-* subtracting providers
-* filtering providers
-
-These common functionality is provided by the +PropertySources+ singleton. Additionally to the base strategies above a +MetaInfo+
-instance can be passed optionally as well to define the meta information for the newly created provider instances.
-Let's assume we have two property providers with the following data:
-
-[source,properties]
-.Provider 1
---------------------------------------------
-a=a
-b=b
-c=c
-g=g
-h=h
-i=i
---------------------------------------------
-
-[source,properties]
-.Provider 2
---------------------------------------------
-a=A
-b=B
-c=C
-d=D
-e=E
-f=F
---------------------------------------------
-
-Looking in detail you see that the entries +a,b,c+ are present in both providers, whereas +d,e,f+ are only present in provider 1,
-and +g,h,i+ only in provider 2.
-
-[source,java]
-.Example Combining PropertySources
---------------------------------------------
-PropertySource provider1 = ...
-PropertySource provider2 = ...
-
-// aggregate, hereby values from provider 2 override values from provider 1
-PropertySource unionOverriding = PropertySources.aggregate(AggregationPolicy.OVERRIDE(), provider1, provider2);
-System.out.println("unionOverriding: " + unionOverriding);
-
-// ignore duplicates, values present in provider 1 are not overriden by provider 2
-PropertySource unionIgnoringDuplicates = PropertySources.aggregate(AggregationPolicy.IGNORE_DUPLICATES(), provider1, provider2);
-System.out.println("unionIgnoringDuplicates: " + unionIgnoringDuplicates);
-
-// this variant combines/maps duplicate values into a new value
-PropertySource unionCombined = PropertySources.aggregate(AggregationPolicy.COMBINE(), provider1, provider2);
-System.out.println("unionCombined: " + unionCombined);
-
-// This variant throws an exception since there are key/value paris in both providers, but with different values
-try{
- PropertySources.aggregate(AggregationPolicy.EXCEPTION(), provider1, provider2);
-}
-catch(ConfigException e){
- // expected!
-}
---------------------------------------------
-
-The example above produces the following outpout:
-
-[source,listing]
-.Example Combining PropertySources
---------------------------------------------
-AggregatedPropertySource{
- (name = dynamicAggregationTests)
- a = "[a][A]"
- b = "[b][B]"
- c = "[c][C]"
- d = "[D]"
- e = "[E]"
- f = "[F]"
- g = "[g]"
- h = "[h]"
- i = "[i]"
-}
-unionOverriding: AggregatedPropertySource{
- (name = <noname>)
- a = "A"
- b = "B"
- c = "C"
- d = "D"
- e = "E"
- f = "F"
- g = "g"
- h = "h"
- i = "i"
-}
-unionIgnoringDuplicates: AggregatedPropertySource{
- (name = <noname>)
- a = "a"
- b = "b"
- c = "c"
- d = "D"
- e = "E"
- f = "F"
- g = "g"
- h = "h"
- i = "i"
-}
-unionCombined: AggregatedPropertySource{
- (name = <noname>)
- a = "a,A"
- b = "b,B"
- c = "c,C"
- d = "D"
- e = "E"
- f = "F"
- g = "g"
- h = "h"
- i = "i"
-}
---------------------------------------------
-
-No +AggregationPolicy+ is also an interface that can be implemented:
-
-[source,java]
-.AggregationPolicy Interface
---------------------------------------------
-@FunctionalInterface
-public interface AggregationPolicy {
- String aggregate(String key, String value1, String value2);
-}
---------------------------------------------
-
-So we can also define our own aggregation strategy using a Lambda expression:
-
-[source,java]
-.Use a Custom AggregationPolicy
---------------------------------------------
-PropertySource provider1 = ...;
-PropertySource provider2 = ...;
-PropertySource props = PropertySources.aggregate(
- (k, v1, v2) -> (v1 != null ? v1 : "") + '[' + v2 + "]",
- MetaInfo.of("dynamicAggregationTests"),
- props1, props2);
-System.out.println(props);
---------------------------------------------
-
-Additionally we also pass here an instance of +MetaInfo+. The output of this code snippet is as follows:
-
-[source,listing]
-.Listing of dynamic aggregation policy
---------------------------------------------
-AggregatedPropertySource{
- (name = dynamicAggregationTests)
- a = "[a][A]"
- b = "[b][B]"
- c = "[c][C]"
- d = "[D]"
- e = "[E]"
- f = "[F]"
- g = "[g]"
- h = "[h]"
- i = "[i]"
-}
---------------------------------------------
-
-Summarizing the +PropertySources+ singleton allows to combine providers in various forms:
-
-[source,listing]
-.Methods provided on PropertySources
---------------------------------------------
-public final class PropertySources {
-
- private PropertySources() {}
-
- public static PropertySource fromArgs(String... args) {
- public static PropertySource fromArgs(MetaInfo metaInfo, String... args) {
- public static PropertySource fromPaths(AggregationPolicy aggregationPolicy, String... paths) {
- public static PropertySource fromPaths(String... paths) {
- public static PropertySource fromPaths(List<String> paths) {
- public static PropertySource fromPaths(AggregationPolicy aggregationPolicy, List<String> paths) {
- public static PropertySource fromPaths(MetaInfo metaInfo, List<String> paths) {
- public static PropertySource fromPaths(AggregationPolicy aggregationPolicy, MetaInfo metaInfo, List<String> paths) {
- public static PropertySource fromUris(URI... uris) {
- public static PropertySource fromUris(AggregationPolicy aggregationPolicy, URI... uris) {
- public static PropertySource fromUris(List<URI> uris) {
- public static PropertySource fromUris(AggregationPolicy aggregationPolicy, List<URI> uris) {
- public static PropertySource fromUris(MetaInfo metaInfo, URI... uris) {
- public static PropertySource fromUris(AggregationPolicy aggregationPolicy, MetaInfo metaInfo, URI... uris) {
- public static PropertySource fromUris(MetaInfo metaInfo, List<URI> uris) {
- public static PropertySource fromUris(AggregationPolicy aggregationPolicy, MetaInfo metaInfo, List<URI> uris) {
- public static PropertySource fromMap(Map<String, String> map) {
- public static PropertySource fromMap(MetaInfo metaInfo, Map<String, String> map) {
- public static PropertySource empty() {
- public static PropertySource emptyMutable() {
- public static PropertySource empty(MetaInfo metaInfo) {
- public static PropertySource emptyMutable(MetaInfo metaInfo) {
- public static PropertySource fromEnvironmentProperties() {
- public static PropertySource fromSystemProperties() {
- public static PropertySource freezed(PropertySource provider) {
- public static PropertySource aggregate(AggregationPolicy mapping, MetaInfo metaInfo, PropertySource... providers){
- public static PropertySource aggregate(PropertySource... providers) {
- public static PropertySource aggregate(List<PropertySource> providers) {
- public static PropertySource aggregate(AggregationPolicy mapping, PropertySource... propertyMaps) {
- public static PropertySource aggregate(AggregationPolicy mapping, List<PropertySource> providers) {
- public static PropertySource mutable(PropertySource provider) {
- public static PropertySource intersected(AggregationPolicy aggregationPolicy, PropertySource... providers) {
- public static PropertySource intersected(PropertySource... providers) {
- public static PropertySource subtracted(PropertySource target, PropertySource... providers) {
- public static PropertySource filtered(Predicate<String> filter, PropertySource provider) {
- public static PropertySource contextual(Supplier<PropertySource> mapSupplier,
- Supplier<String> isolationKeySupplier) {
- public static PropertySource delegating(PropertySource mainMap, Map<String, String> parentMap) {
- public static PropertySource replacing(PropertySource mainMap, Map<String, String> replacementMap) {
-}
---------------------------------------------
-
-
-[[API Configuration]]
-=== Configuration
-==== Basic Model
-
-Configuration inherits all basic features from +PropertySource+, but additionally adds functionality for
-type safety and extension mechanisms:
-
-[source,java]
-.Interface Configuration
---------------------------------------------
-public interface Configuration extends PropertySource{
-
- default OptionalBoolean getBoolean(String key);
- default OptionalInt getInteger(String key);
- default OptionalLong getLong(String key);
- default OptionalDouble getDouble(String key);
- default <T> Optional<T> getAdapted(String key, PropertyAdapter<T> adapter);
- <T> Optional<T> get(String key, Class<T> type);
-
- // accessing areas
- default Set<String> getAreas();
- default Set<String> getTransitiveAreas();
- default Set<String> getAreas(final Predicate<String> predicate);
- default Set<String> getTransitiveAreas(Predicate<String> predicate);
- default boolean containsArea(String key);
-
- // extension points
- default Configuration with(ConfigOperator operator);
- default <T> T query(ConfigQuery<T> query);
-
- // versioning
- default String getVersion(){return "N/A";}
- void addPropertyChangeListener(PropertyChangeListener l);
- void removePropertyChangeListener(PropertyChangeListener l);
-
- // singleton accessors
- public static boolean isDefined(String name);
- public static <T> T current(String name, Class<T> template);
- public static Configuration current(String name);
- public static Configuration current();
- public static <T> T current(Class<T> type){
- public static void configure(Object instance);
- public static String evaluateValue(String expression);
- public static String evaluateValue(Configuration config, String expression);
- public static void addGlobalPropertyChangeListener(PropertyChangeListener listener);
- public static void removeGlobalPropertyChangeListener(PropertyChangeListener listener);
-}
---------------------------------------------
-
-Hereby
-
-* +XXX getXXX(String)+ provide type safe accessors for all basic wrapper types of the JDK.
-* +getAdapted+ allow accessing any type, hereby also passing a +PropertyAdapter+ that converts
- the configured literal value to the type required.
-* +getAreas()+, +getTransitiveAreas()+ allow to examine the hierarchical tree modeled by the configuration tree.
- Optionally also predicates can be passed to select only part of the tree to be returned.
-* +containsArea+ allows to check, if an area is defined.
-* +with, query+ provide the extension points for adding additional functionality.
-
-* the static accessor methods define:
- ** +current(), current(Class), current(String), current(String, Class)+ return the configuration valid for the current runtime environment.
- ** +addPropertyChangeListener, removePropertyChangeListener+ allow to register or unregister
- global config change listener instances.
- ** evaluateValue allows to evaluate a configuration expression based on a given configuration.
- ** +configure+ performs injection of configured values.
-
-[[TypeConversion]]
-==== Type Conversion
-
-Configuration extend +PropertySource+ and add additional support for non String types. This is achieved
-with the help of +PropertyAdapter+ instances:
-
-[source,java]
-.PropertyAdapter
---------------------------------------------
-@FunctionalInterface
-public interface PropertyAdapter<T>{
- T adapt(String value);
-}
---------------------------------------------
-
-PropertyAdapter instances can be implemented manually or registered and accessed from the
-+PropertyAdapers+ singleton. Hereby the exact mechanism is determined by the API backing up the singleton.
-By default corresponding +PropertyAdapter+ instances can be registered using the Java +ServiceLoader+
-mechanism, or programmatically ba calling the +register(Class, PropertyAdapter)+ method.
-
-[source,java]
---------------------------------------------
-public final class PropertyAdapters{
- public static <T> PropertyAdapter<T> register(Class<T> targetType, PropertyAdapter<T> adapter);
- public static boolean isTargetTypeSupported(Class<?> targetType);
- public static <T> PropertyAdapter<T> getAdapter(Class<T> targetType);
- public static <T> PropertyAdapter<T> getAdapter(Class<T> targetType, WithPropertyAdapter annotation);
-}
---------------------------------------------
-
-Whereas this mechanism per se looks not very useful it's power shows up when combining it with the annotations
-API provided, e.g. look at the following annotated class:
-
-[source,java]
-.Annotated Example Class
---------------------------------------------
-public class ConfiguredClass{
-
- @ConfiguredProperty
- private String testProperty;
-
- @ConfiguredProperty("a.b.c.key1")
- @DefaultValue("The current \\${JAVA_HOME} env property is ${env:JAVA_HOME}.")
- String value1;
-
- @ConfiguredProperty("a.b.c.key2")
- private int value2;
-
- @ConfiguredProperty
- @DefaultValue("http://127.0.0.1:8080/res/api/v1/info.json")
- private URL accessUrl;
-
- @ConfiguredProperty
- @DefaultValue("5")
- private Integer int1;
-
- @ConfiguredProperty("a.b.customType")
- private MyCustomType myCustomType;
-
- @ConfiguredProperty("BD")
- private BigDecimal bigNumber;
-
- ...
-}
---------------------------------------------
-
-The class does not show all the possibilities that are provided, but it shows that arbitrary types can be supported easily.
-This applied similarly to collection types, whereas collections are more advanced and therefore described in a separate section
-later.
-
-Given the class above and the current configuration can provide the values required, configuring an instance of the
-class is simple:
-
-[source,java]
-.Configuring the Example Class
---------------------------------------------
-ConfiguredClass classInstance = new ConfiguredClass();
-Configuration.configure(configuredClass);
---------------------------------------------
-
-Additional types can transparently be supported by implementing and registering corresponding SPI instances. This is explained
-in the SPI documentation of {name}.
-
-==== Extension Points
-
-We are well aware of the fact that this library will not be able to cover all kinds of use cases. Therefore
-we have added similar functional extension mechanisms that were used in other areas of the Java eco-system as well:
-
-* +ConfigOperator+ define unary operations on +Configuration+. They can be used for filtering, implementing
- configuration views, security interception etc.
-* +ConfigQuery+ defines a function returning any kind of result based on a configuration instance. Typical
- use cases of queries could be the implementation of configuration SPI instances that are required
- by other libraries or frameworks.
-
-Both interfaces hereby are defined as functional interfaces:
-
-[source,java]
-.ConfigOperator and ConfigQuery
---------------------------------------------
-@FunctionalInterface
-public interface ConfigOperator{
- Configuration operate(Configuration config);
-}
-
-@FunctionalInterface
-public interface ConfigQuery<T>{
- T query(Configuration config);
-}
---------------------------------------------
-
-Both interfaces can be applied on a +Configuration+ instance:
-
-[source,java]
-.Applying Config operators and queries
---------------------------------------------
-Configuration secured = Configuration.of().apply(ConfigSecurity::secure);
-ConfigSecurity securityContext = Configuration.of().query(ConfigSecurity::targetSecurityContext);
---------------------------------------------
-
-NOTE: +ConfigSecurity+ is an arbitrary class.
-
-=== Configuration Injection
-
-The +Configuration+ interface provides static methods that allow to anykind of instances be configured
-ny just passing the instances calling +Configuration.configure(instance);+. The classes passed hereby must
-be annotated with +@ConfiguredProperty+ to define the configured properties. Hereby this annotation can be
-used in multiple ways and combined with other annotations such as +@DefaultValue+,
-+@WithLoadPolicy+, +@WithConfig+, +@WithConfigOperator+, +@WithPropertyAdapter+.
-
-To illustrate the mechanism below the most simple variant of a configured class is given:
-
-[source,java]
-.Most simple configured class
---------------------------------------------
-pubic class ConfiguredItem{
- @ConfiguredProperty
- private String aValue;
-}
---------------------------------------------
-
-When this class is configured, e.g. by passing it to +Configuration.configure(Object)+,
-the following is happening:
-
-* The current valid +Configuration+ is evaluated by calling +Configuration cfg = Configuration.of();+
-* The current property value (String) is evaluated by calling +cfg.get("aValue");+
-* if not successful, an error is thrown (+ConfigException+)
-* On success, since no type conversion is involved, the value is injected.
-* The configured bean is registered as a weak change listener in the config system's underlying
- configuration, so future config changes can be propagated (controllable by applying the
- +@WithLoadPolicy+ annotation).
-
-In the next example we explicitly define the property value:
-[source,java]
---------------------------------------------
-pubic class ConfiguredItem{
-
- @ConfiguredProperty
- @ConfiguredProperty("a.b.value")
- @configuredProperty("a.b.deprecated.value")
- @DefaultValue("${env:java.version}")
- private String aValue;
-}
---------------------------------------------
-
-Within this example we evaluate multiple possible keys. Evaluation is aborted if a key could be successfully
-resolved. Hereby the ordering of the annotations define the ordering of resolution, so in the example above
-resolution equals to +"aValue", "a.b.value", "a.b.deprecated.value"+. If no value could be read
-from the configuration, it uses the value from the +@DefaultValue+ annotation. Interesting here
-is that this value is not static, it is evaluated by calling +Configuration.evaluateValue(Configuration, String)+.
-
-=== Environment
-
-The environment basically is also a kind of property/value provider similar to +System.getProperties()+ and +System
-.getenv()+ in the JDK. Nevertheless it provides additional functionality:
-
-[source,java]
-.Interface Environment
---------------------------------------------
-public interface Environments {
-
- String getEnvironmentType();
- String getEnvironmentId();
- Environment getParentEnvironment();
-
- Optional<String> get(String key);
- boolean containsKey(String key);
- Set<String> keySet();
- Map<String,String> toMap();
-
- public static Environment current(){
- public static Environment getRootEnvironment(){
- public static List<String> getEnvironmentTypeOrder(){
- public static List<String> getEnvironmentHierarchy(){
- public static Optional<Environment> getInstance(String environmentType, String contextId){
- public static Set<String> getEnvironmentContexts(String environmentType){
- public static boolean isEnvironmentActive(String environmentType){
---------------------------------------------
-
-* environments are hierarchical. Hereby all environments inherit from the root environment. The root environment
- hereby must contain
- ** all JDK's system properties, with same keys, values
- ** all JDK's environment properties, prefixed with +env:+.
- ** additional root properties are allowed as well.
-* the root environment is always directly accessible by calling +Environment.getRootEnvironment()+
-* the current environment can be accessed by calling +Environment.of()+.
-* each environment also defines a +Stage+ (implementing +StageSupplier+). Hereby, if not set explicitly the +Stage+ is inherited from the root
- environment. Consequently the root environment must provide a +Stage+, which by default is +Stage.development()+.
-
-Additionally each environment instance is uniquely identified by the environment type (accessible from
-+getEnvironmentType()+ and the environment id (accessible from +getEnvironmentId()+). So it is possible to access
-an +Environment+ by calling +of(String environmentType, String environmentId)+. Implementations may restrict access
-to environments depending on the current runtime environment (runtime context) active. The API does
-not require further aspects.
-
-The call to +getEnvironmentIds(String)+ returns all context ids of the known +Environment+ instances
-of a given type. E.g. assuming there is an environment type +war+ calling +Environment.getEnvironmentIds("war")+
-may return +"/web/app1", "/web/app2"+ (assuming the war context ids equal the web applications root contexts).
-
-All environments are basically ordered. The ordering can be accessed by calling +getEnvironmentTypeOrder()+. Hereby
-not every environment type in a hierarchy must necessarily present. This is reflected by +getEnvironmentHierarchy()+
-which returns the environment type ids in order, but only containing the types of the environments
-currently present and accessible in the hierarchy. As an example an environment type order in an advanced
-use case could be something like +"root","ear","war","saas","user"+, whereas the concrete environment type hierarchy
-may be +"root","war","saas"+, because the application was not included
-in an additional ear archive and no user is currently active (anonymous). The call to +isEnvironmentActive(String)+
-allows to determine if an environment of the given type is currently active.
-Finally the environment hierarchy is of course similarly reflected by the relationship (+getParentEnvironment()+).
-The following code should illustrate some of these concepts:
-
-[source,java]
-.Interface Environment
---------------------------------------------
-List<String> envHierarchy = Environment.getEnvironmentHierarchy();
- // -> "root","war","saas"
-Environment env = Environment.of();
-System.out.println(env.getEnvironmentContext()); // saas
-System.out.println(env.getEnvironmentId()); // mysolution_pro
-env = env.getParentEnvironment();
-System.out.println(env.getEnvironmentContext()); // war
-System.out.println(env.getEnvironmentId()); // pro
-env = env.getParentEnvironment();
-System.out.println(env.getEnvironmentContext()); // root
-System.out.println(env.getEnvironmentId()); // system
-env = env.getParentEnvironment();
-// env is null now!
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-
-