org.springframework.data.hadoop.scripting.Jsr223ScriptEvaluator.java Source code

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Here is the source code for org.springframework.data.hadoop.scripting.Jsr223ScriptEvaluator.java

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/*
 * Copyright 2011 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.data.hadoop.scripting;

import java.io.IOException;
import java.util.Collections;
import java.util.Map;

import javax.script.Bindings;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineFactory;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.SimpleBindings;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.scripting.ScriptCompilationException;
import org.springframework.scripting.ScriptSource;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;

/**
 * Jsr233/javax.scripting implementation of {@link ScriptEvaluator}. 
 * 
 * @author Costin Leau
 */
class Jsr223ScriptEvaluator implements ScriptEvaluator {

    private final Log log = LogFactory.getLog(getClass());

    private String language;
    private String extension;
    private ClassLoader classLoader;

    /**
     * Constructs a new <code>Jsr223ScriptEvaluator</code> instance.
     */
    public Jsr223ScriptEvaluator() {
        this(null);
    };

    /**
     * Constructs a new <code>Jsr223ScriptEvaluator</code> instance.
     *
     * @param classLoader class loader to use
     */
    public Jsr223ScriptEvaluator(ClassLoader classLoader) {
        this.classLoader = classLoader;
    }

    @Override
    public Object evaluate(ScriptSource script) {
        return evaluate(script, Collections.<String, Object>emptyMap());
    }

    @Override
    public Object evaluate(ScriptSource script, Map<String, Object> arguments) {
        ScriptEngine engine = discoverEngine(script, arguments);

        Bindings bindings = (!CollectionUtils.isEmpty(arguments) ? new SimpleBindings(arguments) : null);

        try {
            return (bindings == null ? engine.eval(script.getScriptAsString())
                    : engine.eval(script.getScriptAsString(), bindings));
        } catch (IOException ex) {
            throw new ScriptCompilationException(script, "Cannot access script", ex);
        } catch (ScriptException ex) {
            throw new ScriptCompilationException(script, "Execution failure", ex);
        }
    }

    protected ScriptEngine discoverEngine(ScriptSource script, Map<String, Object> arguments) {
        ScriptEngineManager engineManager = new ScriptEngineManager(classLoader);
        ScriptEngine engine = null;

        if (StringUtils.hasText(language)) {
            engine = engineManager.getEngineByName(language);
        } else {
            // make use the extension (enhanced ScriptSource interface)
            Assert.hasText(extension, "no language or extension specified");
            engine = engineManager.getEngineByExtension(extension);
        }

        Assert.notNull(engine, "No suitable engine found for "
                + (StringUtils.hasText(language) ? "language " + language : "extension " + extension));

        if (log.isDebugEnabled()) {
            ScriptEngineFactory factory = engine.getFactory();
            log.debug(String.format("Using ScriptEngine %s (%s), language %s (%s)", factory.getEngineName(),
                    factory.getEngineVersion(), factory.getLanguageName(), factory.getLanguageVersion()));
        }

        return engine;
    }

    /**
     * Sets the extension of the language meant for evaluation the scripts.. 
     * 
     * @param extension The extension to set.
     */
    public void setExtension(String extension) {
        this.extension = extension;
    }

    /**
     * Sets the name of language meant for evaluation the scripts.
     * 
     * @param language The language to set.
     */
    public void setLanguage(String language) {
        this.language = language;
    }
}