Mercury provides an implementation-neutral way to access GAV-based repositories, including AV repositories, like OSGi. OSGi access is not implemented yet. By access I mean reading artifacts and metadata from repositories and writing artifacts to repositories, metadata is updated by writes.

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.readArtifacts(Collection<ArtifactBasicMetadata> query) - retrieve full-blown Artifact for each query element. Artifacts are charged with pomBytes() and a reference to a local file
  • 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. This call is mostly for dependency tree builder. And of cause - for you, if you find a creative way to utilize it (smile)

Build Details

To write client code that can read and write repositories, declare the following dependencies:

    <dependency>
      <groupId>org.apache.maven.mercury</groupId>
      <artifactId>mercury-repo-local-m2</artifactId>
      <version>${mercury.version}</version>
    </dependency>
    <dependency>
      <groupId>org.apache.maven.mercury</groupId>
      <artifactId>mercury-repo-remote-m2</artifactId>
      <version>${mercury.version}</version>
    </dependency>
    <dependency>
      <groupId>org.apache.maven.mercury</groupId>
      <artifactId>mercury-repo-virtual</artifactId>
      <version>${mercury.version}</version>
    </dependency>

Then assemble an instance of VirtualRepositoryReader for reading from multiple repos, or create a Repository object, obtain RepositoryWriter from it and deploy stuff to that repository for you heart's pleasure.

Sample code from VirtualRepositoryReaderTest

  File             _testBase;
  LocalRepository  _localRepo;
  Server           _server;
  RemoteRepository _remoteRepo;
  VirtualRepositoryReader _vr;


    _testBase = new File( "/my/local/repo" );
    
    _localRepo = new LocalRepositoryM2( "localRepo", _testBase );
    
    _server = new Server( "remoteRepo", new URL("http://repo1.maven.org/maven2") );
    
    _remoteRepo = new RemoteRepositoryM2( _server.getId(), _server );
    
    List<Repository> rl = new ArrayList<Repository>();
    rl.add( _localRepo );
    rl.add( _remoteRepo );
     
    // null dependency processor as I don't use readDependencies()
    _vr = new VirtualRepositoryReader( rl, DependencyProcessor.NULL_PROCESSOR );
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