com.davidbracewell.scripting.ScriptEnvironmentManager.java Source code

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Here is the source code for com.davidbracewell.scripting.ScriptEnvironmentManager.java

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/*
 * (c) 2005 David B. Bracewell
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 com.davidbracewell.scripting;

import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import com.google.common.collect.Maps;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineFactory;
import javax.script.ScriptEngineManager;
import java.util.List;
import java.util.Map;

/**
 * Manages scripting environments giving each language a singleton instance.
 *
 * @author David B. Bracewell
 */
public final class ScriptEnvironmentManager {

    private final Map<String, ScriptEnvironment> environments;
    private final ScriptEngineManager engineManager;

    private static ScriptEnvironmentManager INSTANCE;

    /**
     * @return The instance of ScriptEnvironmentManager
     */
    public static synchronized ScriptEnvironmentManager getInstance() {
        if (INSTANCE == null) {
            INSTANCE = new ScriptEnvironmentManager();
        }
        return INSTANCE;
    }

    private ScriptEnvironmentManager() {
        environments = Maps.newConcurrentMap();
        engineManager = new ScriptEngineManager();
    }

    /**
     * Gets the scripting environment given the environment name.
     *
     * @param environmentName the scripting environment name
     * @return the scripting environment
     */
    public ScriptEnvironment getEnvironment(String environmentName) {
        Preconditions.checkArgument(!Strings.isNullOrEmpty(environmentName),
                "Environment name cannot be null or empty");
        ScriptEngine engine = engineManager.getEngineByName(environmentName);
        environmentName = engine.getFactory().getEngineName();
        if (!environments.containsKey(environmentName)) {
            environments.put(environmentName, new ScriptEnvironment(engine));
        }
        return environments.get(environmentName);
    }

    /**
     * Gets a temporary scripting environment given the environment name.
     *
     * @param environmentName the scripting environment name
     * @return the scripting environment
     */
    public static ScriptEnvironment getTemporaryEnvironment(String environmentName) {
        Preconditions.checkArgument(!Strings.isNullOrEmpty(environmentName),
                "Environment name cannot be null or empty");
        ScriptEngine engine = ScriptEnvironmentManager.getInstance().engineManager.getEngineByName(environmentName);
        return new ScriptEnvironment(engine);
    }

    /**
     * Gets the scripting environment given the script extension.
     *
     * @param extension the scripting environment extension
     * @return the scripting environment
     */
    public ScriptEnvironment getEnvironmentForExtension(String extension) {
        Preconditions.checkArgument(!Strings.isNullOrEmpty(extension), "Extension name cannot be null or empty");
        return getEnvironment(getEnvironmentNameForExtension(extension));
    }

    /**
     * Gets the scripting environment given the script extension.
     *
     * @param extension the scripting environment extension
     * @return the scripting environment
     */
    public static ScriptEnvironment getTemporaryEnvironmentForExtension(String extension) {
        Preconditions.checkArgument(!Strings.isNullOrEmpty(extension), "Extension name cannot be null or empty");
        return getTemporaryEnvironment(
                ScriptEnvironmentManager.getInstance().getEnvironmentNameForExtension(extension));
    }

    /**
     * Gets the scripting environment name given the script extension.
     *
     * @param extension the scripting environment extension
     * @return the scripting environment name
     */
    public String getEnvironmentNameForExtension(String extension) {
        Preconditions.checkArgument(!Strings.isNullOrEmpty(extension), "Extension name cannot be null or empty");
        ScriptEngine engine = engineManager.getEngineByExtension(extension);
        if (engine == null) {
            throw new IllegalStateException(extension + " is not a recognized scripting extension.");
        }
        return engine.getFactory().getLanguageName();
    }

    /**
     * <p> Returns an array whose elements are instances of all the ScriptEngineFactory classes found by the discovery
     * mechanism. </p>
     *
     * @return an array whose elements are instances of all the ScriptEngineFactory classes found by the discovery
     *         mechanism.
     * @see javax.script.ScriptEngineManager#getEngineFactories()
     */
    public List<ScriptEngineFactory> getAvailableEngines() {
        ScriptEngineManager engineManager = new ScriptEngineManager();
        return engineManager.getEngineFactories();
    }

}//END OF ScriptEnvironmentManager