== dependencies
:idprefix: id_ 


This addon *provides classes* for use in other addons. The dependencies addon provides APIs and services for interacting
with artifact repositories, artifact dependencies, and dependency metadata. This is typically for the purpose of 
resolving project libraries and other resources. The dependencies addon provides an abstract API for interacting
with an artifact repository.

=== Depends on

[options="header"]
|===
|Addon |Exported |Optional

|resources
|yes
|no

|===

== Setup

This addon requires the following installation steps.

=== Add configuration to pom.xml 

To use this addon, you must add it as a dependency in the *pom.xml* of your `forge-addon` classified artifact:

<dependency>
   <groupId>org.jboss.forge.addon</groupId>
   <artifactId>dependencies</artifactId>
   <classifier>forge-addon</classifier>
   <version>${version}</version>
</dependency>
      
== Features

Abstraction of Dependency Repository systems::
 The dependencies addon provides a layer of abstraction over native repository systems such as maven, ivy, or even
osgi and java module repositories. This does not mean that all repositories will be compatible via this API; however,
it does mean that methods of interacting with each repository are standardized and consistent. 

DependencyResolver service for dependency resolution::
 The `DependencyResolver` service interface is provided (not implemented) by the dependencies addon, so that other
addons may provide implementations. Addons depending on the dependencies addon may then request service instances
of the `DependencyResolver` and either select a specific resolver, or iterate over the results until a resolver is
capable of handling the given `DependencyQuery`.  
+
[source,java]
----
@Inject 
private DependencyResolver resolver;
...
Set<Dependency> dependencies = resolver.resolveDependencies(...);
DependencyMetadata metadata = resolver.resolveDependencyMetadata(...);
----
+
[TIP] 
====
If your addon uses a container that does not support "@Inject" annotations, services such as the `DependencyResolver` may also be 
accessed via the `AddonRegistry`:

----
AddonRegistry registry = ...
Imported<DependencyResolver> imported = registry.getServices(DependencyResolver.class);
for(ExportedInstance<DependencyResolver> instance : imported)
{
   DependencyResolver resolver = instance.get();
}
----
==== 

Comprehensive dependency query API::
The dependency resolution functions of the dependencies addon functions primarily using the `DependencyQuery` API, with
the fluent `DependencyQueryBuilder` used to specify query criteria.
+
[source,java]
----
DependencyQueryBuilder.create(CoordinateBuilder.create()
      .setGroupId("org.jboss.forge.furnace")
      .setArtifactId("furnace"))
   .setFilter(...)
   .setRepositories(...)
   .setScopeType(...)
----

Consistent programming experience::
 Because the dependencies API provides a consistent set of interfaces for interacting with artifact repositories, 
it is used in a number of addons and should be considered the standard approach for interacting with artifact and
dependency repositories.
