HowTo use Mercury for accessing repositories

Mercury provides an implementation-neutral way to access GAV-based repositories, including AV repositories, like OSGi

APIs

Upper level API works like the following:

• create a bunch of Repository objects
• obtain an instance of DependencyProcessor implementation
  • if you don't plan to use getDependencies call, you can use DependencyProcessor.NULL_PROCESSOR
• create an instance of VirtualRepositoryReader by passing the repositories and dependency processor
• use it

All the calls accept a collection of requests as an input and return an object that hides getResults, that normally is a map< queryElement, Collection<ResultObject> > response. The response object has convenience methos hasExceptions(), hasResults(), getExceptions(), getResults()

One of the key building blocks is a hierarchy of Artifact data:

• ArtifactCoordinates - is truly the 3 components GAV
• ArtifactBasicMetadata - is coordinates plus type/classifier plus convenience methods like hash calculation and such
• ArtifactMetadata adds a list of dependency objects, captured as ArtifactBasicMetadata
• DefaultArtifact implements Artifact interface and adds pomBlob (byte[]) and file, that points to actual binary

Let's assume that you obtained virtual reader in a variable, called vr. The "use it" part means the following:

• vr.readVersions( Collection<ArtifactBasicMetadata> query ) this is the only call that interprets queries. All others treat supplied versions as exact, not as queries.
  • this one takes a collection of queries in the form of ArtifactBasicMetadata and returns a collection of good old ArtifactBasicMetadata ojects. The input object can have a query in the version field
  • version query is now accepted as:
    • 1.2.3 - means any version, higher or equal to 1.2.3, variations:
      • 1.2.3-SNAPSHOT - find latest snapshot of this version
      • 1.2.3-LATEST - find latest snapshot or release of this version
      • 1.2.3-RELEASE - find latest release of this version
    • range in the form of
      • [1.2.3,) this is equal to simple 1.2.3 query
      • (1.2.3,) same as previous, but 1.2.3 version is excluded from results
      • all other obvious variations of /( V1, V2/)
• vr.readDependencies( Collection<ArtifactBasicMetadata> query ) - returns a List<ArtifactBasicMetadata> of dependencies for each element of the query.In other words - it returns an instance of ArtifactMetadata for each ArtifactBasicMetadata from query
• vr.readArtifacts(Collection<ArtifactBasicMetadata> query) - retrieve full-blown Artifact for each query element. Artifacts are charged with pomBytes() and a reference to a local file

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