src/main/java/org/apache/sling/scripting/core/impl/SlingScriptAdapterFactory.java

/*
 * 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 org.apache.sling.scripting.core.impl;

import java.util.Collection;
import java.util.List;

import javax.script.ScriptEngine;

import org.apache.sling.api.adapter.AdapterFactory;
import org.apache.sling.api.resource.Resource;
import org.apache.sling.commons.mime.MimeTypeProvider;
import org.apache.sling.scripting.api.BindingsValuesProvider;
import org.apache.sling.scripting.api.BindingsValuesProvidersByContext;
import org.apache.sling.scripting.api.ScriptCache;
import org.apache.sling.scripting.core.impl.jsr223.SlingScriptEngineManager;
import org.jetbrains.annotations.NotNull;
import org.osgi.framework.BundleContext;
import org.osgi.framework.Constants;
import org.osgi.service.component.ComponentContext;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Reference;

/**
 * AdapterFactory that adapts Resources to the DefaultSlingScript servlet, which
 * executes the Resources as scripts.
 */
@Component(
    service = {
        AdapterFactory.class,
        MimeTypeProvider.class
    },
    property = {
        Constants.SERVICE_VENDOR + "=The Apache Software Foundation",
        Constants.SERVICE_DESCRIPTION + "=Default SlingScriptResolver",
        "adaptables=org.apache.sling.api.resource.Resource",
        "adapters=org.apache.sling.api.scripting.SlingScript",
        "adapters=javax.servlet.Servlet",
        "adapter.condition=If the resource's path ends in an extension registered by a script engine."
    }
)
public class SlingScriptAdapterFactory implements AdapterFactory, MimeTypeProvider {

    private BundleContext bundleContext;

    /** The context string to use to select BindingsValuesProviders */
    public static final String BINDINGS_CONTEXT = BindingsValuesProvider.DEFAULT_CONTEXT;

    /**
     * The service cache for script execution.
     */
    private ServiceCache serviceCache;

    /**
     * The script engine manager.
     */
    @Reference
    private SlingScriptEngineManager scriptEngineManager;

    @Reference
    private volatile SlingScriptEnginePicker scriptEnginePicker;

    /**
     * The BindingsValuesProviderTracker
     */
    @Reference
    private BindingsValuesProvidersByContext bindingsValuesProviderTracker;

    @Reference
    private ScriptCache scriptCache;

    // ---------- AdapterFactory -----------------------------------------------

    @Override
    @SuppressWarnings("unchecked")
    public <AdapterType> AdapterType getAdapter(@NotNull final Object adaptable, @NotNull final Class<AdapterType> type) {

        final Resource resource = (Resource) adaptable;
        final String path = resource.getPath();
        final String extension = path.substring(path.lastIndexOf('.') + 1);

        final List<ScriptEngine> engines = scriptEngineManager.getEnginesByExtension(extension);
        final ScriptEngine engine;
        if (engines.size() == 0) {
            return null;
        } else if (engines.size() == 1) {
            engine = engines.get(0);
        } else {
            engine = scriptEnginePicker.pickScriptEngine(engines, resource, extension);
        }
        if (engine != null) {
            final Collection<BindingsValuesProvider> bindingsValuesProviders = bindingsValuesProviderTracker.getBindingsValuesProviders(engine.getFactory(), BINDINGS_CONTEXT);
            // unchecked cast
            return (AdapterType) new DefaultSlingScript(this.bundleContext, resource, engine, bindingsValuesProviders, this.serviceCache, scriptCache);
        }

        return null;
    }

    // ---------- MimeTypeProvider

    /**
     * Returns the first MIME type entry of the supported MIME types of a
     * ScriptEngineFactory which is registered for the extension of the given
     * name. If no ScriptEngineFactory is registered for the given extension or
     * the registered ScriptEngineFactory is not registered for a MIME type,
     * this method returns <code>null</code>.
     *
     * @param name The name whose extension is to be mapped to a MIME type. The
     *            extension is the string after the last dot in the name. If the
     *            name contains no dot, the entire name is considered the
     *            extension.
     */
    @Override
    public String getMimeType(String name) {
        name = name.substring(name.lastIndexOf('.') + 1);
        ScriptEngine se = scriptEngineManager.getEngineByExtension(name);
        if (se != null) {
            List<?> mimeTypes = se.getFactory().getMimeTypes();
            if (mimeTypes != null && mimeTypes.size() > 0) {
                return String.valueOf(mimeTypes.get(0));
            }
        }

        return null;
    }

    /**
     * Returns the first extension entry of the supported extensions of a
     * ScriptEngineFactory which is registered for the given MIME type. If no
     * ScriptEngineFactory is registered for the given MIME type or the
     * registered ScriptEngineFactory is not registered for an extensions, this
     * method returns <code>null</code>.
     *
     * @param mimeType The MIME type to be mapped to an extension.
     */
    @Override
    public String getExtension(String mimeType) {
        ScriptEngine se = scriptEngineManager.getEngineByMimeType(mimeType);
        if (se != null) {
            List<?> extensions = se.getFactory().getExtensions();
            if (extensions != null && extensions.size() > 0) {
                return String.valueOf(extensions.get(0));
            }
        }

        return null;
    }

    // ---------- SCR integration ----------------------------------------------

    protected void activate(ComponentContext context) {
        bundleContext = context.getBundleContext();
        this.serviceCache = new ServiceCache(this.bundleContext);
    }

    protected void deactivate(ComponentContext context) {
        this.serviceCache.dispose();
        this.serviceCache = null;
        this.bundleContext = null;
    }
}