org.jclouds.scriptbuilder.functionloader.osgi.BundleFunctionLoader.java Source code

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Here is the source code for org.jclouds.scriptbuilder.functionloader.osgi.BundleFunctionLoader.java

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/*
 * 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.jclouds.scriptbuilder.functionloader.osgi;

import java.io.IOException;
import java.net.URL;
import java.util.Enumeration;
import java.util.Properties;

import org.jclouds.scriptbuilder.domain.OsFamily;
import org.jclouds.scriptbuilder.domain.ShellToken;
import org.jclouds.scriptbuilder.functionloader.FunctionLoader;
import org.jclouds.scriptbuilder.functionloader.FunctionNotFoundException;
import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceRegistration;

import com.google.common.base.Charsets;
import com.google.common.io.Resources;

/**
 * A {@link FunctionLoader} which searches for functions in the {@link Bundle} resources.
 */
public class BundleFunctionLoader implements FunctionLoader {

    private final BundleContext bundleContext;
    private ServiceRegistration registration;

    /**
     * Constructor
     * 
     * @param bundleContext
     */
    public BundleFunctionLoader(BundleContext bundleContext) {
        this.bundleContext = bundleContext;
    }

    /**
     * Starts the loader. Looks up for {@link Bundle} resources and registers itself in the service
     * registry. It adds a property to the service which advertise all the functions found in the
     * local resources.
     */
    public void start() {
        Bundle bundle = bundleContext.getBundle();
        Enumeration<?> entries = bundle.findEntries("/functions/", "*.*", false);
        StringBuilder sb = new StringBuilder();
        while (entries.hasMoreElements()) {
            URL url = (URL) entries.nextElement();
            String function = url.getFile();
            sb.append(function);
            if (entries.hasMoreElements()) {
                sb.append(" ");
            }
        }
        String functions = sb.toString();
        registerFunction(functions);
    }

    /**
     * Unregisters itself from the service registry.
     */
    public void stop() {
        registration.unregister();
    }

    /**
     * Loads the function from the {@link Bundle} resources.
     * 
     * @param function
     *           The function name to load.
     * @param family
     *           This operating system family of the function.
     * @return
     * @throws FunctionNotFoundException
     */
    @Override
    public String loadFunction(String function, OsFamily family) throws FunctionNotFoundException {
        try {
            return Resources.toString(bundleContext.getBundle().getResource(
                    String.format("/functions/%s.%s", function, ShellToken.SH.to(family))), Charsets.UTF_8);
        } catch (IOException e) {
            throw new FunctionNotFoundException(function, family, e);
        }
    }

    private void registerFunction(String functions) {
        Properties properties = new Properties();
        properties.put("function", functions);
        registration = bundleContext.registerService(FunctionLoader.class.getName(), this, properties);
    }

}