/*
* Hibernate Validator, declare and validate application constraints
*
* License: Apache License, Version 2.0
* See the license.txt file in the root directory or <http://www.apache.org/licenses/LICENSE-2.0>.
*/
package org.hibernate.validator.internal.util.scriptengine;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import static org.hibernate.validator.internal.util.logging.Messages.MESSAGES;
/**
* Factory responsible for the creation of {@link ScriptEvaluator}s. This
* class is thread-safe.
*
* @author Gunnar Morling
* @author Kevin Pollet <kevin.pollet@serli.com> (C) 2011 SERLI
*/
public class ScriptEvaluatorFactory {
/**
* A reference with an instance of this factory. Allows the factory to be reused several times, but can be GC'ed if required.
*/
private static Reference<ScriptEvaluatorFactory> INSTANCE = new SoftReference<ScriptEvaluatorFactory>( new ScriptEvaluatorFactory() );
/**
* A cache of script executors (keyed by language name).
*/
private final ConcurrentMap<String, ScriptEvaluator> scriptExecutorCache = new ConcurrentHashMap<String, ScriptEvaluator>();
private ScriptEvaluatorFactory() {
}
/**
* Retrieves an instance of this factory.
*
* @return A script evaluator factory. Never null.
*/
public static synchronized ScriptEvaluatorFactory getInstance() {
ScriptEvaluatorFactory theValue = INSTANCE.get();
if ( theValue == null ) {
theValue = new ScriptEvaluatorFactory();
INSTANCE = new SoftReference<ScriptEvaluatorFactory>( theValue );
}
return theValue;
}
/**
* Retrieves a script executor for the given language.
*
* @param languageName The name of a scripting language as expected by {@link ScriptEngineManager#getEngineByName(String)}.
*
* @return A script executor for the given language. Never null.
*
* @throws ScriptException In case no JSR 223 compatible engine for the given language could be found.
*/
public ScriptEvaluator getScriptEvaluatorByLanguageName(String languageName) throws ScriptException {
if ( !scriptExecutorCache.containsKey( languageName ) ) {
ScriptEvaluator scriptExecutor = createNewScriptEvaluator( languageName );
scriptExecutorCache.putIfAbsent( languageName, scriptExecutor );
}
return scriptExecutorCache.get( languageName );
}
/**
* Creates a new script executor for the given language.
*
* @param languageName A JSR 223 language name.
*
* @return A newly created script executor for the given language.
*
* @throws ScriptException In case no JSR 223 compatible engine for the given language could be found.
*/
private ScriptEvaluator createNewScriptEvaluator(String languageName) throws ScriptException {
ScriptEngine engine = new ScriptEngineManager().getEngineByName( languageName );
if ( engine == null ) {
throw new ScriptException( MESSAGES.unableToFindScriptEngine( languageName ) );
}
return new ScriptEvaluator( engine );
}
}