Component state and registry - Drivers support

A component with "drivers" will initialise/start its drivers after it is
initialised/started itself. It will also stop/destroy non-driver reverse
dependencies before stopping/destroying its drivers.

TODO

@@ -1,8 +1,7 @@
 To Do:
- * Test for ComponentState.{init,destroy}
+ * Test for ComponentState.{init,destroy} and driver-related stuff
  * Registry tests
  * Registry doc
- * Implement "DriverFor" support
  * General usage documentation
  * Uncouple component-provided names from the library
  * Automatically-updated singletons
@@ -12,3 +11,4 @@ To Do:
 Other ideas (maybe later if needed):
  * Unregistering components
  * Hierarchy of registries
+ * Driver-related helpers (e.g. determine type of driver components, register/unregister drivers with main)

src/main/java/info/ebenoit/ebul/cmp/ComponentRegistry.java

@@ -197,6 +197,15 @@ public class ComponentRegistry
 			nLeft -= found;
 		}
 
+		// Set up driver components
+		for ( int i = 0 ; i < nAdd ; i++ ) {
+			TempBuildRec c = adding.get( i );
+			String df = c.info.getDriverFor( );
+			if ( df != null ) {
+				c.state.setDriverFor( byName.get( df ) );
+			}
+		}
+
 		// Inject and track dependencies
 		injectDependencies( adding );
 
@@ -446,6 +455,7 @@ public class ComponentRegistry
 		}
 	}
 
+
 	private void destroyComponent( int index )
 			throws ComponentDestructionException
 	{

src/main/java/info/ebenoit/ebul/cmp/ComponentState.java

@@ -44,6 +44,11 @@ public final class ComponentState
 	/** State records for the component's reverse dependencies */
 	private final HashSet< ComponentState > reverseDependencies = new HashSet< >( );
 
+	/** State records for the component's drivers */
+	private final HashSet< ComponentState > drivers = new HashSet< >( );
+	/** Main component (i.e. component this component is a driver for) */
+	private ComponentState mainComponent;
+
 	/** Lifecycle actions for the current component */
 	@SuppressWarnings( "rawtypes" )
 	private final ThrowingConsumer[] lcActions;
@@ -217,7 +222,8 @@ public final class ComponentState
 	 * If the component is already active, nothing is done. If it is inactive, the method will try starting the
 	 * component's dependencies, then call the startup action if one is configured.
 	 * <p>
-	 * If the method succeeds, the component will be marked as active.
+	 * If these actions succeed, the component will be marked as active. Then, if the component has drivers, they will
+	 * be started as well.
 	 * 
 	 * @throws ComponentStartupException
 	 *             if an exception occurs while running the startup action for this component or for one of its
@@ -246,8 +252,8 @@ public final class ComponentState
 	 * Stops the component
 	 * <p>
 	 * This method attempts to shut down the component. If the component has reverse dependencies, it will start by
-	 * shutting them down. Then it will call the configured shutdown action, if there is one. If both steps succeed, it
+	 * shutting them down (stopping "normal" reverse dependencies first, then shutting down drivers). Then it will call
-	 * will mark the component as inactive.
+	 * the configured shutdown action, if there is one. If both steps succeed, it will mark the component as inactive.
 	 * <p>
 	 * If the method is called on an inactive component, nothing will happen.
 	 * 
@@ -269,7 +275,12 @@ public final class ComponentState
 		assert this.initialised;
 
 		for ( final ComponentState rdepState : this.reverseDependencies ) {
-			rdepState.stop( );
+			if ( !this.drivers.contains( rdepState ) ) {
+				rdepState.stop( );
+			}
+		}
+		for ( final ComponentState drvState : this.drivers ) {
+			drvState.stop( );
 		}
 		this.runLifecycleAction( LifecycleStage.STOP );
 		this.active = false;
@@ -301,7 +312,8 @@ public final class ComponentState
 	 * Initialises the component
 	 * <p>
 	 * This method attempts to initialise a component. It makes sure that all of the component's dependencies have been
-	 * initialised, then executes the lifecycle action for the {@link LifecycleStage#INITIALISE INITIALISE} stage.
+	 * initialised, then executes the lifecycle action for the {@link LifecycleStage#INITIALISE INITIALISE} stage. Then,
+	 * if the component has drivers, it initialises them.
 	 * 
 	 * @throws ComponentInitialisationException
 	 *             if an error occurs while executing an initialisation action
@@ -323,6 +335,9 @@ public final class ComponentState
 		}
 		this.runLifecycleAction( LifecycleStage.INITIALISE );
 		this.initialised = true;
+		for ( final ComponentState drvState : this.drivers ) {
+			drvState.init( );
+		}
 	}
 
 
@@ -330,7 +345,8 @@ public final class ComponentState
 	 * Destroys the component
 	 * <p>
 	 * This method attempts to destroy a component. It makes sure that all of the component's reverse dependencies have
-	 * been destroyed, then executes the lifecycle action for the {@link LifecycleStage#DESTROY DESTROY} stage.
+	 * been destroyed (starting with "normal" reverse dependencies, then processing the drivers), then executes the
+	 * lifecycle action for the {@link LifecycleStage#DESTROY DESTROY} stage.
 	 * 
 	 * @throws ComponentDestructionException
 	 *             if an error occurs while executing a destruction action
@@ -351,7 +367,12 @@ public final class ComponentState
 		}
 
 		for ( final ComponentState rdepState : this.reverseDependencies ) {
-			rdepState.destroy( );
+			if ( !this.drivers.contains( rdepState ) ) {
+				rdepState.destroy( );
+			}
+		}
+		for ( final ComponentState drvState : this.drivers ) {
+			drvState.destroy( );
 		}
 		this.runLifecycleAction( LifecycleStage.DESTROY );
 		this.initialised = false;
@@ -375,6 +396,23 @@ public final class ComponentState
 	}
 
 
+	/**
+	 * Sets a component as the one this component is a driver for.
+	 * <p>
+	 * This will also update the main component to add this component as a driver.
+	 * 
+	 * @param main
+	 *            the main component
+	 */
+	void setDriverFor( final ComponentState main )
+	{
+		assert main.registry == this.registry;
+		assert this.mainComponent == null;
+		this.mainComponent = main;
+		main.drivers.add( this );
+	}
+
+
 	/**
 	 * Executes a lifecycle action.
 	 * <p>
@@ -438,15 +476,24 @@ public final class ComponentState
 		for ( final ComponentState depState : this.dependencies ) {
 			depState.startNoChecks( );
 		}
+		if ( this.active ) {
+			// If the current component is a driver, it will have been started by its main component, so we need to
+			// avoid re-executing the start action.
+			return;
+		}
 		this.runLifecycleAction( LifecycleStage.START );
 		this.active = true;
+		for ( final ComponentState drvState : this.drivers ) {
+			drvState.startNoChecks( );
+		}
 	}
 
 
 	/**
 	 * Internal component restart method
 	 * <p>
-	 * Attempts to restart a component if it was active before {@link #restart()} was called.
+	 * Attempts to restart a component if it was active before {@link #restart()} was called. Calls the start action
+	 * first, then restart the drivers, then other reverse dependencies.
 	 * 
 	 * @throws ComponentStartupException
 	 *             if an exception occurs while running the startup action for this component or for one of its reverse
@@ -457,6 +504,9 @@ public final class ComponentState
 	{
 		if ( this.wasActive ) {
 			this.runLifecycleAction( LifecycleStage.START );
+			for ( final ComponentState drvState : this.drivers ) {
+				drvState.startIfPreviouslyActive( );
+			}
 			for ( final ComponentState rDepState : this.reverseDependencies ) {
 				rDepState.startIfPreviouslyActive( );
 			}