plugins/org.eclipse.objectteams.osgi.weaving/src/org/eclipse/objectteams/internal/osgi/weaving/TeamLoader.java

/**********************************************************************
 * This file is part of "Object Teams Development Tooling"-Software
 * 
 * Copyright 2013 GK Software AG
 *  
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Please visit http://www.objectteams.org for updates and contact.
 * 
 * Contributors:
 * 	Stephan Herrmann - Initial API and implementation
 **********************************************************************/
package org.eclipse.objectteams.internal.osgi.weaving;

import static org.eclipse.objectteams.otequinox.Activator.log;

import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.eclipse.jdt.annotation.Nullable;
import org.eclipse.objectteams.internal.osgi.weaving.AspectBindingRegistry.WaitingTeamRecord;
import org.eclipse.objectteams.otequinox.ActivationKind;
import org.eclipse.objectteams.otequinox.hook.ILogger;
import org.objectteams.ITeam;
import org.objectteams.Team;
import org.osgi.framework.Bundle;

/**
 * This class triggers the actual loading/instantiation/activation of teams.
 * <p>
 * It implements a strategy of deferring those teams where instantiation/activation
 * failed (NoClassDefFoundError), which assumably happens, if one required class
 * cannot be loaded, because its loading is already in progress further down in
 * our call stack.
 * </p><p>
 * Which teams participate in deferred instantiation is communicated via the list
 * {@link #deferredTeams}.
 * </p>
 */
public class TeamLoader {

	private List<WaitingTeamRecord> deferredTeams;
	
	/** did we record the fact that a team needs deferring? */
	boolean needDeferring; 
	
	public TeamLoader(List<WaitingTeamRecord> deferredTeams) {
		this.deferredTeams = deferredTeams;
	}

	/** Team loading, 1st attempt (trying to do all three phases load/instantiate/activate). */
	public boolean loadTeams(Bundle aspectBundle, AspectBinding aspectBinding, String className) {
		Collection<String> teamsForBase = aspectBinding.getTeamsForBase(className);
		if (teamsForBase == null) return true;
		for (String teamForBase : teamsForBase) {
			// Load:
			Class<? extends ITeam> teamClass;
			teamClass = findTeamClass(teamForBase, aspectBundle);
			if (teamClass == null) {
				log(new ClassNotFoundException("Not found: "+teamForBase), "Failed to load team "+teamForBase);
				continue;
			}
			// Instantiate?
			ActivationKind activationKind = aspectBinding.getActivation(teamForBase);
			if (activationKind == ActivationKind.NONE)
				continue;
			ITeam teamInstance = instantiateTeam(aspectBinding, teamClass, teamForBase);
			if (teamInstance == null)
				continue;
			// Activate?
			activateTeam(aspectBinding, teamForBase, teamInstance, activationKind);
		}
		return !needDeferring; // TODO, need to figure out whether we're done with aspectBinding.
	}

	/** Team loading, subsequent attempts. */
	public void instantiateWaitingTeam(WaitingTeamRecord record)
			throws InstantiationException, IllegalAccessException 
	{
		ITeam teamInstance = record.teamInstance;
		String teamName = record.getTeamName();
		if (teamInstance == null) {
			// Instantiate (we only get here if activationKind != NONE)
			teamInstance = instantiateTeam(record.aspectBinding, record.teamClass, teamName);
			if (teamInstance == null)
				return;
		}
		// Activate?
		ActivationKind activationKind = record.aspectBinding.getActivation(teamName);
		activateTeam(record.aspectBinding, teamName, teamInstance, activationKind);
	}

	public static Pair<URL,String> findTeamClassResource(String className, Bundle bundle) {
		for (String candidate : possibleTeamNames(className)) {
			URL result = bundle.getResource(candidate.replace('.', '/')+".class");
			if (result != null)
				return new Pair<>(result, candidate);
		}
		return null;
	}

	@SuppressWarnings("unchecked")
	public static Class<? extends ITeam> findTeamClass(String className, Bundle bundle) {
		for (String candidate : possibleTeamNames(className)) {
			try {
				Class<?> result = bundle.loadClass(candidate);
				if (result != null)
					return (Class<? extends ITeam>) result;
			} catch (NoClassDefFoundError|ClassNotFoundException e) {
				// keep looking
			}
		}
		return null;
	}

	/** 
	 * Starting from currentName compute a list of potential binary names of (nested) teams
	 * using "$__OT__" as the separator, to find class parts of nested teams.  
	 */
	public static List<String> possibleTeamNames(String currentName) {
		List<String> result = new ArrayList<String>();
		result.add(currentName);
		char sep = '.'; // assume source name
		if (currentName.indexOf('$') > -1)
			// binary name
			sep = '$';
		int from = currentName.length()-1;
		while (true) {
			int pos = currentName.lastIndexOf(sep, from);
			if (pos == -1)
				break;
			String prefix = currentName.substring(0, pos); 
			String postfix = currentName.substring(pos+1);
			if (sep=='$') {
				if (!postfix.startsWith("__OT__"))
					result.add(0, currentName = prefix+"$__OT__"+postfix);
			} else {
				// heuristic: 
				// only replace if parent element looks like a class (expected to start with uppercase)
				int prevDot = prefix.lastIndexOf('.');
				if (prevDot > -1 && Character.isUpperCase(prefix.charAt(prevDot+1))) 
					result.add(0, currentName = prefix+"$__OT__"+postfix);
				else 
					break;
			}
			from = pos-1;
		}
		return result;
	}

	private @Nullable ITeam instantiateTeam(AspectBinding aspectBinding, Class<? extends ITeam> teamClass, String teamName) {
		try {
			ITeam instance = teamClass.newInstance();
			log(ILogger.INFO, "Instantiated team "+teamName);
			return instance;
		} catch (NoClassDefFoundError ncdfe) {
			needDeferring = true;
			synchronized(deferredTeams) {
				deferredTeams.add(new WaitingTeamRecord(teamClass, aspectBinding, ncdfe.getMessage().replace('/','.')));
			}
		} catch (Throwable e) {
			// application error during constructor execution?
			log(e, "Failed to instantiate team "+teamName);
		}
		return null;
	}

	private void activateTeam(AspectBinding aspectBinding, String teamName, ITeam teamInstance, ActivationKind activationKind)
	{
		// don't try to activate before all base classes successfully load.
		ClassLoader loader = teamInstance.getClass().getClassLoader();
		for (String baseclass : aspectBinding.basesPerTeam.get(teamName)) {
			try {
				loader.loadClass(baseclass);
			} catch (ClassNotFoundException cnfe) {
				synchronized (deferredTeams) {
					deferredTeams.add(new WaitingTeamRecord(teamInstance, aspectBinding, baseclass)); // TODO(SH): synchronization, deadlock?
				}
				return;
			}
		}
		// good to go, so go:
		try {
			switch (activationKind) {
			case ALL_THREADS:
				teamInstance.activate(Team.ALL_THREADS);
				break;
			case THREAD:
				teamInstance.activate();
				break;
			//$CASES-OMITTED$
			default:
				break;
			}
		} catch (Throwable t) {
			// application errors during activation
			log(t, "Failed to activate team "+teamName);
		}
	}
}