External Filter Chain Definitions

  public void contributeService( DeploymentContext context, Service service ) throws Exception {
    String chain = null; // Default if null, otherwise specific chain name defined in topoloy.xml
    Map<String,Map<String,String>> params = null; // Default if null, otherwise map of per provider role map of name/value pairs.  
    ResourceDescriptor resource = context.addResource()
    resource.role( "WEBHDFS" );
    resource.pattern( "webhdfs/v1/?**" );
    resource.pattern( "webhdfs/v1/**?**" );
    context.contributeChain( service, resource, chain, params );
  }

<topology>
  <gateway>
    <provider/>
    <chain name="">
      <provider role="" name="">
        <param name="" value=""/>
      </provider>
      <provider/>
    </chain>
  </gateway>
</topology>

public interface DeploymentContext {

  GatewayConfig getGatewayConfig();

  Topology getTopology();

  WebArchive getWebArchive();

  WebAppDescriptor getWebAppDescriptor();

  GatewayDescriptor getGatewayDescriptor();

  void contributeChain(
      Service service,
      ResourceDescriptor resource,
      String chainName,
      List<ServiceParamDescriptor> params );

  void addDescriptor( String name, Object descriptor );

  <T> T getDescriptor( String name );
}

public interface ServiceDeploymentContributor {

  // The role of this service deployment contributor.  e.g. WEBHDFS
  String getRole();

  // The name of this service deployment contributor.  Not used yet.
  String getName();

  // Called after provider initializeContribution methods and in arbitrary order relative to other service contributors.
  void initializeContribution( DeploymentContext context );

  // Called per service based on the service's role.
  // Returns a list of resources it added to the descriptor.
  void contributeService( DeploymentContext context, Service service ) throws Exception;

  // Called after all contributors and before provider finalizeContribution methods.
  void finalizeContribution( DeploymentContext context );

}

public interface ProviderDeploymentContributor {

  // The role this provider supports (e.g. authentication)
  String getRole();

  // In the topology the provider will have an optional name element.  If it is present
  // then the framework will look for the the provider deployment contributor with the correct
  // role and name.
  String getName();

  // All provider initializeContribution methods are called first in arbitrary order.
  void initializeContribution( DeploymentContext context );

  // Called for each provider in the topology based on the role and optionally name.
  void contributeProvider( DeploymentContext context, Provider provider );

  // This will be called indirectly by a ServiceDeploymentContributor when it needs a filter
  // contributed for this providers role.  A ServiceDeploymentContributor may request a specific
  // provider by role and name otherwise the default provider for the role will be used.
  void contributeFilter(
      DeploymentContext context,
      Provider provider,
      Service service,
      ResourceDescriptor resource,
      List<FilterParamDescriptor> params );

  // All provider finalizeContribution methods are called last in arbitrary order.
  void finalizeContribution( DeploymentContext context );