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configuration in a unified way both in SE and EE. EE may provide additional +mechanism, such as injection, but the SE mechanisms should work as well, so any code written in SE is fully +portable to EE as well. +This can only be achieved by providing a static accessor, e.g.</p> +</div> +<div class="listingblock"> +<div class="content"> +<pre class="prettyprint highlight"><code class="language-java" data-lang="java">Configuration config = Configuration.current();</code></pre> +</div> +</div> +<div class="paragraph"> +<p>The call above should work exactly the same in EE. To enable this the static call must be delegated in the +internals of the singleton, depending on the runtime. In EE the executing component can behave contextually, +or even be loaded within the CDI environment (at least for post loading, application runtime aspects, but not earlier).</p> +</div> +<div class="paragraph"> +<p>Additionally in EE it should also be possible to inject Configuration, which gives you the same results as the call +above:</p> +</div> +<div class="listingblock"> +<div class="content"> +<pre class="prettyprint highlight"><code class="language-java" data-lang="java">@Inject +private Configuration cfg;</code></pre> +</div> +</div> +</div> +<div class="sect2"> +<h3 id="_simple_lookup_of_properties">Simple Lookup of Properties</h3> +<div class="paragraph"> +<p>Users just want to create a configuration ad hoc, from given property files. The +files could be locally in the file system, on the classpath.</p> +</div> +<div class="paragraph"> +<p>Tamaya should provide a simple Java API for accessing key/value based configuration. Hereby users want to access +properties as simple String values.</p> +</div> +<div class="paragraph"> +<p>Hereby returning Java 8 Optional values must be considered as well, instead of returning null.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_value_placeholders">Value Placeholders</h3> +<div class="paragraph"> +<p>Users just want to to be able to add placeholders to the values of configuration (not the keys). The mechanisms for +resolving the placeholders hereby should be not constraint to one single lanmguage like EL. Instead of different +replacement strategies should be selectable, e.g. by prefixing an expression with the name of the resolver that +should do the work (eg "blabla ${env:HOME} using Java version ${sys:java.version}.". +This allows resolution mechanism to be isolated easily and also allows to use simpler mechanisms, if no more complex +ones like EL are required. This is especially useful to deal with low resource environment like ME.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_type_safe_properties">Type Safe Properties</h3> +<div class="paragraph"> +<p>Users just want to access properties not only as Strings, but let Tamaya do the conversion to the required +or the configred target type. By defauklt all java.ui.lang wrapper and primitive types should be supported, but also +other common types like date/time types, math numeric types and more.</p> +</div> +<div class="paragraph"> +<p>It must be possible that users can register their own custom types.</p> +</div> +<div class="paragraph"> +<p>Finally users also want to be able to dynamically provide or override type adaption (conversion), when reading a value, +for a certain key/value pair.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_configuration_templates">Configuration Templates</h3> +<div class="paragraph"> +<p>Users want to be able to let Tamaya implement an interface template based on configuration. +This use case is pretty similar to the injection use case. Basically the values are not injected, +but cached within the template proxy returned, e.g. as DynamicValue. +Similarly it could even be possible to define callback methods (default methods) +or register listeners to DynamicValue instances returned.</p> +</div> +<div class="paragraph"> +<p>Templates hereby can easily be managed, but provide a excellent mechanism to provide type-safe configuration +to clients in a very transparent way. Details can be controlled by using the same annotations as for +normal configuration injection.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_java_8_functional_support">Java 8 Functional Support</h3> +<div class="paragraph"> +<p>Users want to be able to benefit from the new programming styles introduced with Java 8. Configuration +should provide extension points for different aspects, where additional code can be hooked in easily. +In short: were possible functional interfaces should be modelled.</p> +</div> +<div class="paragraph"> +<p>Examples:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>code that converts a configuration to another kind of configuration: UnaryOperator<Configuration></p> +</li> +<li> +<p>code that creates any kind of result based on a configuration: Function<Configuration,T></p> +</li> +<li> +<p>Adapters for type conversion are defined as Function<String,T></p> +</li> +<li> +<p>Key, value filters ccan be modelled as BiFunction<String,String,String></p> +</li> +<li> +<p>etc.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_configuration_locations">Configuration Locations</h3> +<div class="paragraph"> +<p>Users want to be able to</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>read configuration from different locations.</p> +</li> +<li> +<p>By default classpath and file resources are +supported. But similarly remote access using a JSON ReST call should be possible.</p> +</li> +<li> +<p>Tamaya should define a JSON and XML format for configuration.</p> +</li> +<li> +<p>Configuration locations should be scannable using ant-styled resource patterns, if possible.</p> +</li> +<li> +<p>Scanning and reading logic can be modularized by using a ConfigReader interface.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_configuration_formats">Configuration Formats</h3> +<div class="paragraph"> +<p>Users want to be able to use the format they prefer.</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>properties, xml-properties and ini-format should be supported by default</p> +</li> +<li> +<p>Other/custom formats should be easily addable by registering or providing the format on configuration evaluation (read).</p> +</li> +<li> +<p>When possible Tamaya should figure out which format to be used and how the InputStream should be correctly +interpreted.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_multiple_configurations">Multiple Configurations</h3> +<div class="paragraph"> +<p>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.</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>Different code modules, libraries, plugins or products want to have their "own" separated configuration.</p> +</li> +<li> +<p>Similar it should be possible to add fully specific additional configurations.</p> +</li> +</ul> +</div> +<div class="paragraph"> +<p>The default configuration hereby should always be present, whereas additional configurations are optional. +Users want to be able to check the availability of such an additional configuration.</p> +</div> +<div class="paragraph"> +<p>Of course, additional configuration must be identifiable. The best way to do is to be discussed, nevertheless the +mechanism must not depend on Java EE and the identifying keys must be serializable easily. +Basically simple names are sufficient and woukld provide exact this required functionality.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_external_configuration">External Configuration</h3> +<div class="paragraph"> +<p>Users want to be able to replace, override, extend or adapt any parts or all of an existing configuration from +external sources. +This also must be the case for multi-context environments, where the context identifiers are +the only way to link to the correct remote configuration.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_context_dependent_configuration">Context Dependent Configuration</h3> +<div class="paragraph"> +<p>In multi tenancy setups or complex systems a hierarchical/graph model of contexts for configurations is required, or different runtime contexts are executed in parallel +within the same VN. What sounds normal for EE also may be the case for pure SE environments:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>Users want to be able to model different layers of runtime context</p> +</li> +<li> +<p>Users want to identiofy the current layer, so configuration used may be adapted.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_dynamic_provisioning_uc8">Dynamic Provisioning (UC8)</h3> +<div class="paragraph"> +<p>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</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>creating new nodes (using IaaS services)</p> +</li> +<li> +<p>deploying and starting the required runtime platform , e.g. as part of a PaaS solution.</p> +</li> +<li> +<p>deploying and starting the application modules.</p> +</li> +</ul> +</div> +<div class="paragraph"> +<p>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:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>provide remote capabilities for configuration</p> +</li> +<li> +<p>allow configuration to be updated remotely.</p> +</li> +<li> +<p>allow client code to listen for configuration changes and react as needed.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_minimal_property_source_spi">Minimal Property Source SPI</h3> +<div class="paragraph"> +<p>Users expect that implementing an additional configuration property source is as easy as possible. +So there should be an SPI defined that allows any kind of data source to be used for providing configuration data. +The interface to be implemented is expected to be minimal to reduce the implementation burden. Default +methods should be used where possible, so only a few methods are expected to be required to implement.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_scannable_properties">Scannable Properties</h3> +<div class="paragraph"> +<p>If possible configuration should be scannable, meaning it should be possible to evaluate the keys available. +The corresponding capabilities should be accessible by a isScannable() method.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_combine_configurations">Combine Configurations</h3> +<div class="paragraph"> +<p>Users want to be able to combine different configurations to a new configuration instance. +Hereby the resulting configuration can be</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>a union of both, ignoring duplicates (and optionally log them)</p> +</li> +<li> +<p>a union of both, duplicates are ignored</p> +</li> +<li> +<p>a union of both, conflicts are thrown as ConfigException</p> +</li> +<li> +<p>an intersection of both, containing only keys present and equal in both configurations</p> +</li> +<li> +<p>an arbitrary mapping or filter, modelled by an CombinationPolicy, which basically can be modelled +as BiFunction<String, String, String>, hereby</p> +<div class="ulist"> +<ul> +<li> +<p>a result of null will remove the key</p> +</li> +<li> +<p>any other result will use the value returned as final value of the combination.</p> +</li> +</ul> +</div> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_mx_rest_management">MX/ReST Management</h3> +<div class="paragraph"> +<p>Users want to be have comprehensive management support, which should allow</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>to change configuration</p> +</li> +<li> +<p>to remove configuration</p> +</li> +<li> +<p>to view configuration and its provider details</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_adaptable_service_context">Adaptable Service Context</h3> +<div class="paragraph"> +<p>Tamaya should support an adaptable ServiceContext to resolve any kind of implememntation services, both API services as core +framework services. The ServiceContext should be dynamically replecable by configuring an alternate instance of +using the Java *ServiceContet+.</p> +</div> +<div class="paragraph"> +<p>This decouples component usage from its load and management part and als greatly simplifies integration with +new/alternate runtime environments. +The service context is exptected to provide</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>single singleton instances: these service can be cached.</p> +</li> +<li> +<p>access to multiple instances which implement some commons SPI interface.</p> +</li> +<li> +<p>as useful priorization of components is done by the model itself.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_configuration_injection">Configuration Injection</h3> +<div class="paragraph"> +<p>Users want to be able to polulate configured items by injecting configured values. Hereby</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>the lifecycle of the instances is not managed by Tamaya</p> +</li> +<li> +<p>all references to items configured are managed as weak references, to prevent memoryleaks.</p> +</li> +<li> +<p>Injection should if possible evaluate the properties by defaults. Even properties without +any annotations are possible.</p> +</li> +<li> +<p>Users expect to exclude certain properties from calculation</p> +</li> +<li> +<p>Beside injection of properties it is also possible to call setter methods with one parameter similarly.</p> +</li> +<li> +<p>Basically injection is performed, when the instance is passed to the Tamaya configuration system. It should also +be possible to inject/provide final values, especially Strings. Changes on configured values should be +reflected in the current value. Setters methods similarly can be called again, with the new values, on changes.</p> +</li> +<li> +<p>Users expect to control dynamic values and recall of setter methods, basically the following strategies should be +supported:</p> +<div class="ulist"> +<ul> +<li> +<p>inject only once and ignore further changes.</p> +</li> +<li> +<p>reinject/reinitialize on each change</p> +</li> +</ul> +</div> +</li> +<li> +<p>Dynamic Values can easily be modeled as ConfiguredValue instances, which should have the following functionality:</p> +<div class="ulist"> +<ul> +<li> +<p>access the current value</p> +</li> +<li> +<p>access the new value</p> +</li> +<li> +<p>access the latest value access time in ms</p> +</li> +<li> +<p>access the latest value update time in ms</p> +</li> +<li> +<p>evaluate easily if the value has changed since the last access</p> +</li> +<li> +<p>accept the change</p> +<div class="ulist"> +<ul> +<li> +<p>as a shortcut it should be possible to accept the change on access of the value implicitly, hereby always accessing +the latest valid value.</p> +</li> +</ul> +</div> +</li> +<li> +<p>ignore the change</p> +</li> +<li> +<p>register Consumer<DynamicValue> liasteners to listen on the changes (ans also removing them later again).</p> +</li> +</ul> +</div> +</li> +</ul> +</div> +<div class="paragraph"> +<p>All observing functionality can be done completely asynchronously and in parallel.</p> +</div> +</div> +</div> +</div> +<div class="sect1"> +<h2 id="Requirements">Requirements</h2> +<div class="sectionbody"> +<div class="sect2"> +<h3 id="_core_configuration_requirements">Core Configuration Requirements</h3> +<div class="sect3"> +<h4 id="_general">General</h4> +<div class="paragraph"> +<p>Tamaya must provide a Java SE API for accessing key/value based configuration. Hereby</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>Configuration is modelled by an interface</p> +</li> +<li> +<p>Configuration is organized as key/value pairs, using a subset of functionality present on Map<String,String> as +follows:</p> +<div class="ulist"> +<ul> +<li> +<p>access a value by key (get)</p> +</li> +<li> +<p>check if a value is present (containsKey)</p> +</li> +<li> +<p>get a set of all defined keys (keySet)</p> +</li> +<li> +<p>a configuration must be convertible to a Map, by calling toMap()</p> +</li> +<li> +<p>a configuration must provide access to its meta information.</p> +</li> +</ul> +</div> +</li> +<li> +<p>Configuration value access methods must never return null.</p> +</li> +<li> +<p>The API must support undefined values.</p> +</li> +<li> +<p>The API must support passing default values, to be returned if a value is undefined.</p> +</li> +<li> +<p>The API must allow to throw exceptions, when a value is undefined. Customized exceptions hereby should be supported.</p> +</li> +<li> +<p>Properties can be stored in the classpath, on a file or accessible by URL.</p> +</li> +<li> +<p>Properties can be stored minimally in properties, xml-properties or ini-format.</p> +</li> +</ul> +</div> +</div> +<div class="sect3"> +<h4 id="_minimalistic_property_source">Minimalistic Property Source</h4> +<div class="paragraph"> +<p>For enabling easy integration of custom built configuration sources a minimalistic API/SPI must be defined, that</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>is modelled by an interface</p> +</li> +<li> +<p>is a minimal subset of Configuration necessary to implement a configuration.</p> +</li> +<li> +<p>must be convertible to a "Configuration+.</p> +</li> +</ul> +</div> +</div> +<div class="sect3"> +<h4 id="_extension_points">Extension Points</h4> +<div class="paragraph"> +<p>For supporting more complex scenarios, Configuration</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>must implement the composite pattern, meaning new Configuration instances can be created by combining existing +configurations.</p> +</li> +<li> +<p>must be adaptable, by creating a new configuration by applying a UnaryOperator<COnfiguration> to it.</p> +</li> +<li> +<p>must be queryable, by passing a ConfigQuery to an Configuration instance.</p> +</li> +</ul> +</div> +</div> +<div class="sect3"> +<h4 id="_type_safety">Type Safety</h4> +<div class="paragraph"> +<p>Besides Strings Configuration should also support the following types:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>Primitive types</p> +</li> +<li> +<p>Wrapper types</p> +</li> +<li> +<p>All other types (by using a PropertyAdapter</p> +</li> +</ul> +</div> +<div class="paragraph"> +<p>Hereby type conversion should be done as follows:</p> +</div> +<div class="olist arabic"> +<ol class="arabic"> +<li> +<p>Check if for the given target type an explicit adapter is registered, if so, use the registered adapter.</p> +</li> +<li> +<p>If no adapter is present, check if the target type T has static methods called T of(String), T getInstance(String), T valueOf(String), T from(String). If so +use this method to create the non value of T.</p> +</li> +<li> +<p>Check if the target type has a constructor T(String). If so, try to instantiate an instance using the constructor.</p> +</li> +<li> +<p>Give up, throw a IllegalArgument exception.</p> +</li> +</ol> +</div> +</div> +</div> +<div class="sect2"> +<h3 id="_configuration_fomats">Configuration Fomats</h3> +<div class="paragraph"> +<p>By default Tamaya support the following configuration formats:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>.properties</p> +</li> +<li> +<p>.xml properties</p> +</li> +<li> +<p>.ini files</p> +</li> +</ul> +</div> +<div class="paragraph"> +<p>It must be possible to add additional formats by registering them with the current ServiceContext.</p> +</div> +</div> +<div class="sect2"> +<h3 id="_mutability">Mutability</h3> +<div class="ulist"> +<ul> +<li> +<p>Configurations can be mutable, mutability can be accessed as a property.</p> +</li> +<li> +<p>Configuration can be changed by collecting the changes into a ConfigCHangeSet and apply this set to the +given Configuration instance.</p> +</li> +<li> +<p>Besides the points above, Configuration is immutable.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_serializability_and_immutability_of_configuration">Serializability and Immutability of Configuration</h3> +<div class="ulist"> +<ul> +<li> +<p>Configuration is modelled as a service. Therefore serialization may not work. This can be mitigated by adding +a freeze feature, where the know key/value pairs are extracted into an immutable and serializable form.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_configuration_combination_requirements">Configuration Combination Requirements</h3> +<div class="paragraph"> +<p>At least the following composition policies must be supported:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>override: subsequent entries override existing ones.</p> +</li> +<li> +<p>aggregate-exception: key/values were added, in case of conflicts a ConfigException must be thrown.</p> +</li> +<li> +<p>aggregate-ignore-duplicates: similar to union, whereas duplicates are ignored (leaving the initial value loaded).</p> +</li> +<li> +<p>aggregate-combine: conflicting entries were resolved by adding them both to the target configuration by +redefining partial keys.</p> +</li> +<li> +<p>custom: any function determining the key/values to be kept must be possible</p> +</li> +</ul> +</div> +<div class="paragraph"> +<p>When combining configuration it must also be possible to override (file/classpath) configuration by</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>system properties.</p> +</li> +<li> +<p>command line arguments.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_configuration_injection_2">Configuration Injection</h3> +<div class="paragraph"> +<p>As metnioned configuration can be injected by passing a unconfigured instance of an annotated class to the +Configuration.configure static method:</p> +</div> +<div class="listingblock"> +<div class="title">Configuring a POJO</div> +<div class="content"> +<pre class="prettyprint highlight"><code class="language-java" data-lang="java">MyPojo instance = new MyPojo(); +Configuration.configure(instance);</code></pre> +</div> +</div> +<div class="paragraph"> +<p>Hereby +* It must be possible to define default values to be used, if no valid value is present. +* It must be possible to define dynamic expressions, at least for default values. +* The values configured can be reinjected, if the underlying configuration changes. This should also be the case + for final classes, such as Strings. +* Reinjection should be controllable by an loading policy. +* It must be possible to evaluate multiple keys, e.g. current keys, and as a backup deprecated keys + from former application releases. +* It must be possible to evaluate multiple configurations. +* The type conversion of the properties injected must be configurable, by defining a PropertyAdapter. +* The value evaluated for a property (before type conversion) must be adaptable as well. +* It must be possible to observe configuration changes.</p> +</div> +<div class="paragraph"> +<p>The following annotations must be present at least:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p><strong>@ConfiguredProperty</strong> defining the key of the property to be evaluated. It takes an optional value, defining the +property name. It must be possible to add multiple annotations of this kind to define an order of evaluation +of possible keys.</p> +</li> +<li> +<p><strong>@DefaultValue</strong> (optional) defines a default String value, to be used, when no other key is present.</p> +</li> +<li> +<p><strong>@WithConfig</strong> (optional) defines the name of the configuration to be used. Similar to @ConfiguredProperty multiple +configuration can be defined for lookup.</p> +</li> +<li> +<p><strong>@WithConfigOperator</strong> allows to adapt the String value evaluated, <strong>before</strong> it is passed as input to injection or +type conversion.</p> +</li> +<li> +<p><strong>@WithPropertyAdapter</strong> allows to adapt the conversion to the required target type, hereby overriding any default +conversion in place.</p> +</li> +<li> +<p><strong>@WithLoadPolicy</strong> allows to define the policy for (re)injection of configured values.</p> +</li> +<li> +<p><strong>@ObservesConfigChange</strong> allows to annotate methods that should be called on configuration changes.</p> +</li> +<li> +<p>*@DefaultAreas" allows to define a key prefix key to be used for the configured key, if no absolute key +is defined.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="_configuration_templates_2">Configuration Templates</h3> +<div class="paragraph"> +<p>For type safe configuration clients should be able to define an interface and let it implement by the +configuration system based on Configuration available:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>Clients define an interface and annotate it as required (similar to above)</p> +</li> +<li> +<p>The interface methods must not take any arguments</p> +</li> +<li> +<p>The configuration system can be called to return such an interface implementation.</p> +</li> +<li> +<p>The configuration system returns a proxy hereby providing type-safe access the values required.</p> +</li> +<li> +<p>Similar to configured types also templates support multiple values and custom adapters.</p> +</li> +<li> +<p>It is possible to listen on configuration changes for templates, so users of the templates +may react on configuration changes.</p> +</li> +</ul> +</div> +<div class="paragraph"> +<p>The following snippet illustrates the requirements:</p> +</div> +<div class="listingblock"> +<div class="title">Type Safe Configuration Template Example</div> +<div class="content"> +<pre class="prettyprint highlight"><code class="language-java" data-lang="java">public interface MyConfig { + + @ConfiguredProperty("myCurrency") + @DefaultValue("CHF") + String getCurrency(); + + @ConfiguredProperty("myCurrencyRate") + Long getCurrencyRate(); + + @ConfigChange + default configChanged(ConfigChange event){ + ... + } + +}</code></pre> +</div> +</div> +<div class="paragraph"> +<p>Templates can be accessed by calling the Configuration.current(Class) method:</p> +</div> +<div class="listingblock"> +<div class="title">Accessing a type safe Configuration Template</div> +<div class="content"> +<pre class="prettyprint highlight"><code class="language-java" data-lang="java">MyConfig config = Configuration.current(MyConfig.class);</code></pre> +</div> +</div> +</div> +<div class="sect2"> +<h3 id="RequirementsServer">Server Configuration Requirements</h3> +<div class="ulist"> +<ul> +<li> +<p>Ensure Configuration can be transferred over the network easily.</p> +</li> +<li> +<p>Beside serializability text based formats for serialization in XML and JSON must be defined.</p> +</li> +<li> +<p>A management API must be defined, which allows to inspect the configuration in place, e.g. using +JMX or REST services.</p> +</li> +</ul> +</div> +<div id="RequirementsJavaEE" class="paragraph"> +<p>Java EE leads to the following requirements:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>Configuration must be contextual, depending on the current runtime context (e.g. boot level, ear, war, …​).</p> +</li> +<li> +<p>Hereby contextual aspects can even exceed the levels described above, e.g. for SaaS scenarios.</p> +</li> +<li> +<p>Resources can be unloaded, e.g. wars, ears can be restarted.</p> +</li> +<li> +<p>The different contextual levels can also be used for overriding, e.g. application specific configuration +may override ear or system configuration.</p> +</li> +<li> +<p>Configuration may be read from different sources (different classloaders, files, databases, remote locations).</p> +</li> +<li> +<p>Configuration may be read in different formats (deployment descriptors, ServiceLoader configuration, alt-DD feature, …​)</p> +</li> +<li> +<p>JSF also knows the concept of stages.</p> +</li> +<li> +<p>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.</p> +</li> +<li> +<p>In general it would be useful to model the Environment explicitly.</p> +</li> +<li> +<p>Configuration used as preferences is writable as well. This requires mutability to be modelled in way, without the +need of synchronization.</p> +</li> +<li> +<p>JNDI can be used for configuration as well.</p> +</li> +</ul> +</div> +<div id="RequirementsMultitenancy" class="paragraph"> +<p>Configurations made in the tenant or user layer override the default app configuration etc., so</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>It must be possible to structure Configuration in layers that can override/extend each other.</p> +</li> +<li> +<p>The current environment must be capable of mapping tenant, user and other aspects, so a corresponding configuration +(or layer) can be derived.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="RequirementsExtensions">Extensions Requirements</h3> +<div class="paragraph"> +<p>It must be possible to easily add additional functionality by implementing external functional interfaces operating +on Configuration.</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>UnaryOperator<Configuration> for converting into other version of Configuration.</p> +</li> +<li> +<p>ConfigQuery<T> extending Function<T, Configuration>.</p> +</li> +</ul> +</div> +</div> +<div class="sect2"> +<h3 id="RequirementsNonFunctional">Non Functional Requirements</h3> +<div class="paragraph"> +<p>THe following non-functional requirements must be met:</p> +</div> +<div class="ulist"> +<ul> +<li> +<p>tbd</p> +</li> +</ul> +</div> +</div> +</div> +</div></p> + + <hr /> + </div> + </div> + <div> + <div id="push"></div> + + <div id="footer"> + <div class="container"> + <p class="muted credit">© 2014-2016 Apache Software Foundation | Mixed with <a href="http://getbootstrap.com/";>Bootstrap v3.1.1</a> + | Baked with <a href="http://jbake.org";>JBake <span>v2.5.0</span></a> + at <span>2016-10-31</span> + </p> + <p> + <b>Disclaimer</b> + Apache Tamaya (incubating) is an effort undergoing + incubation at + The Apache Software Foundation (ASF), sponsored by + the name of Apache Incubator. Incubation is required of + all newly accepted projects until a further review indicates + that the infrastructure, communications, and decision making + process have stabilized in a manner consistent with other + successful ASF projects. While incubation status is not + necessarily a reflection of the completeness or stability of + the code, it does indicate that the project has yet to + be fully endorsed by the ASF.<br /> + <a href="http://incubator.apache.org/guides/website.html"; style="border:0px;" target="_target"><img class="incubator-logo" src="logos/egg-logo2.png"/></a> + </p> + </div> + </div> + + <!-- Le javascript + ================================================== --> + <!-- Placed at the end of the document so the pages load faster --> + <script src="js/jquery-1.11.1.min.js"></script> + <script src="js/bootstrap.min.js"></script> + <script src="js/prettify.js"></script> + + </div> + </body> +</html>
