-/*
- * Copyright 2007 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.wamblee.system;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
-
-/**
- * Assembler to control multiple subsystems. It makes sure that all dependencies
- * are met and controls the order in which systems are initialized.
- *
- * @author Erik Brakkee
- */
-public class SystemAssembler {
-
- private static final Log LOG = LogFactory.getLog(SystemAssembler.class);
-
- private static final String ROOT_CONTEXT_NAME = "root";
- private String _context;
- private Component[] _systems;
- private ProvidedInterface[] _required;
-
- public static RequiredInterface[] filterRequiredServices(
- ProvidedInterface aProvided,
- Collection<RequiredInterface> aDescriptors) {
- List<RequiredInterface> required = new ArrayList<RequiredInterface>();
- for (RequiredInterface descriptor : aDescriptors) {
- if (descriptor.implementedBy(aProvided)) {
- required.add(descriptor);
- }
- }
- return required.toArray(new RequiredInterface[0]);
- }
-
- public static ProvidedInterface[] filterProvidedServices(
- RequiredInterface aRequired,
- Collection<ProvidedInterface> aProvided) {
- List<ProvidedInterface> provided = new ArrayList<ProvidedInterface>();
- for (ProvidedInterface descriptor : aProvided) {
- if (aRequired.implementedBy(descriptor)) {
- provided.add(descriptor);
- }
- }
- return provided.toArray(new ProvidedInterface[0]);
- }
-
- /**
- * Constructs the assembler.
- *
- * @param aSystems
- * Systems that must be assembled.
- * @param aAvailableServices
- * Available services from other systems outside of the systems
- * that this assembler manages.
- */
- public SystemAssembler(Component[] aSystems,
- ProvidedInterface[] aAvailableServices) {
- this(ROOT_CONTEXT_NAME, aSystems, aAvailableServices);
- }
-
- /**
- * Constructs the assembler.
- *
- * @param aContext
- * Context (unique name) of the assembler.
- * @param aSystems
- * Systems that must be assembled.
- * @param aAvailableServices
- * Available services from other systems outside of the systems
- * that this assembler manages.
- */
- public SystemAssembler(String aContext, Component[] aSystems,
- ProvidedInterface[] aAvailableServices) {
- _context = aContext;
- _systems = aSystems;
- _required = aAvailableServices;
- validate();
- }
-
- /**
- * Determines if the systems are ordered appropriately so that all
- * dependencies are met.
- */
- private void validate()
- throws SystemAssemblyException {
-
- List<ProvidedInterface> allProvided = new ArrayList<ProvidedInterface>();
- for (ProvidedInterface descriptor : _required) {
- allProvided.add(descriptor);
- }
- for (Component system : _systems) {
- // Check if all required services are already provided by earlier
- // systems.
- RequiredInterface[] required = system.getRequiredServices();
-
- for (RequiredInterface descriptor : required) {
- ProvidedInterface[] filtered = filterProvidedServices(
- descriptor, allProvided);
-
- if (filtered.length == 0) {
- throw new SystemAssemblyException(
- "Service '"
- + descriptor
- + "' required by system '"
- + system
- + "' is not provided by systems that are started earlier");
- }
- if (filtered.length > 1) {
- throw new SystemAssemblyException(
- "Service '"
- + descriptor
- + "' required by system '"
- + system
- + "' matches multiple services provided by other systems: " +
- Arrays.asList(filtered));
- }
- }
-
- // add all provided services
- ProvidedInterface[] provided = system.getProvidedServices();
- allProvided.addAll(Arrays.asList(provided));
- }
- }
-
- /**
- * Starts the subsystems.
- *
- * @param aRequiredServices
- * Services that are available from other systems that have been
- * started before.
- */
- public void start() {
- LOG.info("Starting '" + _context + "'");
- Set<ProvidedInterface> allProvided = new HashSet<ProvidedInterface>();
- allProvided.addAll(Arrays.asList(_required));
-
- for (Component system : _systems) {
-
- // Compose a list of the required services required for the subsystem.
-
- RequiredInterface[] descriptors = system
- .getRequiredServices();
- List<ProvidedInterface> services = new ArrayList<ProvidedInterface>();
- for (RequiredInterface required : descriptors) {
- ProvidedInterface[] provided = filterProvidedServices(
- required, allProvided);
- assert provided.length == 1;
- services.add(provided[0]);
- required.setProvider(provided[0]);
- }
-
- // Start the service.
- system.start(_context);
-
- // Add started services to the set of started services.
- for (ProvidedInterface service : system.getProvidedServices()) {
- allProvided.add(service);
- }
-
- }
- }
-
-}