/*
* Copyright 2002-2016 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.springframework.scripting.support;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.script.Bindings;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineFactory;
import javax.script.ScriptEngineManager;
import javax.script.SimpleBindings;
/**
* Common operations for dealing with a JSR-223 {@link ScriptEngine}.
*
* @author Juergen Hoeller
* @since 4.2.2
*/
public abstract class StandardScriptUtils {
/**
* Retrieve a {@link ScriptEngine} from the given {@link ScriptEngineManager}
* by name, delegating to {@link ScriptEngineManager#getEngineByName} but
* throwing a descriptive exception if not found or if initialization failed.
* @param scriptEngineManager the ScriptEngineManager to use
* @param engineName the name of the engine
* @return a corresponding ScriptEngine (never {@code null})
* @throws IllegalArgumentException if no matching engine has been found
* @throws IllegalStateException if the desired engine failed to initialize
*/
public static ScriptEngine retrieveEngineByName(ScriptEngineManager scriptEngineManager, String engineName) {
ScriptEngine engine = scriptEngineManager.getEngineByName(engineName);
if (engine == null) {
Set<String> engineNames = new LinkedHashSet<>();
for (ScriptEngineFactory engineFactory : scriptEngineManager.getEngineFactories()) {
List<String> factoryNames = engineFactory.getNames();
if (factoryNames.contains(engineName)) {
// Special case: getEngineByName returned null but engine is present...
// Let's assume it failed to initialize (which ScriptEngineManager silently swallows).
// If it happens to initialize fine now, alright, but we really expect an exception.
try {
engine = engineFactory.getScriptEngine();
engine.setBindings(scriptEngineManager.getBindings(), ScriptContext.GLOBAL_SCOPE);
}
catch (Throwable ex) {
throw new IllegalStateException("Script engine with name '" + engineName +
"' failed to initialize", ex);
}
}
engineNames.addAll(factoryNames);
}
throw new IllegalArgumentException("Script engine with name '" + engineName +
"' not found; registered engine names: " + engineNames);
}
return engine;
}
static Bindings getBindings(Map<String, Object> bindings) {
return (bindings instanceof Bindings ? (Bindings) bindings : new SimpleBindings(bindings));
}
}