/* Copyright (2012) Schibsted ASA
* This file is part of Possom.
*
* Possom is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Possom is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Possom. If not, see <http://www.gnu.org/licenses/>.
*/
package no.sesat.search.query.token;
import java.lang.ref.Reference;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import no.sesat.commons.ioc.BaseContext;
import no.sesat.commons.ref.ReferenceMap;
import no.sesat.search.query.QueryStringContext;
import no.sesat.search.site.Site;
import no.sesat.search.site.SiteContext;
import no.sesat.search.site.SiteKeyedFactory;
import no.sesat.search.site.SiteKeyedFactoryInstantiationException;
import no.sesat.search.site.config.BytecodeLoader;
import no.sesat.search.site.config.ResourceContext;
import no.sesat.search.site.config.SiteClassLoaderFactory;
import no.sesat.search.site.config.Spi;
import org.apache.log4j.Logger;
/** EvaluatorFactory responsible to finding appropriate factory subclass to use given the context.
*
* Any implementing EvaluatorFactory provides two main methods
* isResponsibleFor(token)
* getEvaluator(token)
* which are used by primarily by the TokenEvaluationEngine to find applicable evaluators and to use them.
*
* SKER3540
* @version $Id$
*/
public abstract class AbstractEvaluatorFactory{
/**
* The context the RegExpEvaluatorFactory must work against.
*/
public interface Context extends BaseContext, ResourceContext, SiteContext, QueryStringContext {
/** Fully qualified classname for the factory responsible for finding related evaluators.
* @return the fully qualified factory classname.
*/
String getEvaluatorFactoryClassName();
/** A uniqueId for the request.
* Is not mission critical, ie can be left leave blank.
* @return the uniqueId
*/
String getUniqueId();
}
// Constants -----------------------------------------------------
private static final Logger LOG = Logger.getLogger(AbstractEvaluatorFactory.class);
private static final String ERR_MUST_USE_CONTEXT_CONSTRUCTOR = "Must use constructor that supplies a context!";
// Attributes ----------------------------------------------------
private final Context context;
private static final int WEAK_CACHE_INITIAL_CAPACITY = 16;
private static final float WEAK_CACHE_LOAD_FACTOR = 0.5f;
private static final int WEAK_CACHE_CONCURRENCY_LEVEL = 16;
/**
* Unsynchronized are there are no 'changing values', just existance or not of the Constructor in the system.
*/
private static final Map<Site,ReferenceMap<String,Constructor<? extends AbstractEvaluatorFactory>>> WEAK_CACHE
= new ConcurrentHashMap<Site,ReferenceMap<String,Constructor<? extends AbstractEvaluatorFactory>>>();
// Static --------------------------------------------------------
/** find the appropriate factory subclass to use given the context.
*
* @param cxt supplied context.
* @return the appropriate factory subclass.
*/
@SuppressWarnings("unchecked")
public static final AbstractEvaluatorFactory instanceOf(final Context cxt) {
final Site site = cxt.getSite();
final String clsName = cxt.getEvaluatorFactoryClassName();
ReferenceMap<String,Constructor<? extends AbstractEvaluatorFactory>> weakCache = WEAK_CACHE.get(site);
if(null == weakCache){
weakCache = new ReferenceMap<String,Constructor<? extends AbstractEvaluatorFactory>>(
ReferenceMap.Type.WEAK,
new ConcurrentHashMap<String,Reference<Constructor<? extends AbstractEvaluatorFactory>>>(
WEAK_CACHE_INITIAL_CAPACITY,
WEAK_CACHE_LOAD_FACTOR,
WEAK_CACHE_CONCURRENCY_LEVEL));
WEAK_CACHE.put(site, weakCache);
}
Constructor<? extends AbstractEvaluatorFactory> s = weakCache.get(clsName);
// We cannot cache the EvaluatorFactory instances so easily because each depends on the QueryString.
// the cache would then need to be keyed on Site->FactoryClassName->QueryString
// Effective and safe caching becomes difficult when each QueryString has such a short lifespan.
// It is more effective than to let each EvaluatorFactory provide it's own QueryString caching.
// Note: The TokenEvaluationEnginImpl instance does contain a weak cache
// since the instance is based on a Site and QueryString combination.
try {
if(null == s){
final SiteClassLoaderFactory f = SiteClassLoaderFactory.instanceOf(createClassLoadingContext(cxt));
final Class clazz = f.getClassLoader().loadClass(clsName);
s = clazz.getConstructor(Context.class);
weakCache.put(clsName, s);
}
return s.newInstance(cxt);
}catch (InstantiationException ex) {
throw new IllegalArgumentException("Unable to construct AbstractEvaluatorFactory: " + clsName, ex);
}catch (IllegalAccessException ex) {
throw new IllegalArgumentException("Unable to construct AbstractEvaluatorFactory: " + clsName, ex);
}catch (IllegalArgumentException ex) {
throw new IllegalArgumentException("Unable to construct AbstractEvaluatorFactory: " + clsName, ex);
}catch (InvocationTargetException ex) {
throw new IllegalArgumentException("Unable to construct AbstractEvaluatorFactory: " + clsName, ex);
}catch (NoSuchMethodException ex) {
throw new IllegalArgumentException("Unable to construct AbstractEvaluatorFactory: " + clsName, ex);
}catch (SecurityException ex) {
throw new IllegalArgumentException("Unable to construct AbstractEvaluatorFactory: " + clsName, ex);
}catch(ClassNotFoundException ex){
throw new IllegalArgumentException("Unable to construct AbstractEvaluatorFactory: " + clsName, ex);
}
}
// Constructors --------------------------------------------------
/**
* Illegal Constructor. Must use AbstractEvaluatorFactory(SiteContext).
*/
private AbstractEvaluatorFactory() {
throw new IllegalArgumentException(ERR_MUST_USE_CONTEXT_CONSTRUCTOR);
}
/** All factory implementations must super to this in their constructor.
* @param context the supplied context to work within.
* @throws SiteKeyedFactoryInstantiationException if factory construction fails.
*/
protected AbstractEvaluatorFactory(final Context context) throws SiteKeyedFactoryInstantiationException{
this.context = context;
}
// Public --------------------------------------------------------
/**
* Is the factory responsibe for evaluation of this TokenPredicate.
* Default implementation checks that getEvaluator(..) does not return ALWAYS_FALSE_EVALUATOR
* @param token the TokenPredicate we're checking
* @return true if factory is responsible for evaluating the given TokenPredicate.
*/
public boolean isResponsibleFor(final TokenPredicate token){
try {
return TokenEvaluationEngineImpl.ALWAYS_FALSE_EVALUATOR != getEvaluator(token);
}catch (EvaluationException ex) {
LOG.error("failed trying to find evaluator", ex);
return false;
}
}
/**
* If the evaluator is not found in this site it will fallback and look in the parent site.
* @param token the predicate the evaluator is to be used for
* @return the TokenEvaluator to use. Or TokenEvaluationEngineImpl.ALWAYS_FALSE_EVALUATOR if not found.
* @throws EvaluationException
*/
public abstract TokenEvaluator getEvaluator(final TokenPredicate token) throws EvaluationException;
// Z implementation ----------------------------------------------
// Y overrides ---------------------------------------------------
// Package protected ---------------------------------------------
// Protected -----------------------------------------------------
/** Obtain the context we're working within.
*
* @return the context.
*/
protected final Context getContext(){
return context;
}
// Private -------------------------------------------------------
private static SiteClassLoaderFactory.Context createClassLoadingContext(final Context context) {
return new no.sesat.search.site.config.SiteClassLoaderFactory.Context() {
public BytecodeLoader newBytecodeLoader(SiteContext siteContext, String className, String jarFileName) {
return context.newBytecodeLoader(siteContext, className, jarFileName);
}
public Site getSite() {
return context.getSite();
}
public Spi getSpi() {
return Spi.QUERY_EVALUATION;
}
};
}
// Inner classes -------------------------------------------------
}