src/main/java/org/apache/felix/main/Main.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.felix.main;

import java.io.*;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.*;
import org.apache.felix.framework.Felix;
import org.apache.felix.framework.util.FelixConstants;
import org.apache.felix.framework.util.Util;
import org.osgi.framework.Constants;
import org.osgi.framework.launch.Framework;

/**
 * <p>
 * This class is the default way to instantiate and execute the framework. It is not
 * intended to be the only way to instantiate and execute the framework; rather, it is
 * one example of how to do so. When embedding the framework in a host application,
 * this class can serve as a simple guide of how to do so. It may even be
 * worthwhile to reuse some of its property handling capabilities.
 * </p>
**/
public class Main
{
    /**
     * The property name used to specify an URL to the system
     * property file.
    **/
    public static final String SYSTEM_PROPERTIES_PROP = "felix.system.properties";
    /**
     * The default name used for the system properties file.
    **/
    public static final String SYSTEM_PROPERTIES_FILE_VALUE = "system.properties";
    /**
     * The property name used to specify an URL to the configuration
     * property file to be used for the created the framework instance.
    **/
    public static final String CONFIG_PROPERTIES_PROP = "felix.config.properties";
    /**
     * The default name used for the configuration properties file.
    **/
    public static final String CONFIG_PROPERTIES_FILE_VALUE = "config.properties";
    /**
     * Name of the configuration directory.
     */
    public static final String CONFIG_DIRECTORY = "conf";

    private static Framework m_felix = null;

    /**
     * <p>
     * This method performs the main task of constructing an framework instance
     * and starting its execution. The following functions are performed
     * when invoked:
     * </p>
     * <ol>
     *   <li><i><b>Read the system properties file.<b></i> This is a file
     *       containing properties to be pushed into <tt>System.setProperty()</tt>
     *       before starting the framework. This mechanism is mainly shorthand
     *       for people starting the framework from the command line to avoid having
     *       to specify a bunch of <tt>-D</tt> system property definitions.
     *       The only properties defined in this file that will impact the framework's
     *       behavior are the those concerning setting HTTP proxies, such as
     *       <tt>http.proxyHost</tt>, <tt>http.proxyPort</tt>, and
     *       <tt>http.proxyAuth</tt>. Generally speaking, the framework does
     *       not use system properties at all.
     *   </li>
     *   <li><i><b>Perform system property variable substitution on system
     *       properties.</b></i> Any system properties in the system property
     *       file whose value adheres to <tt>${&lt;system-prop-name&gt;}</tt>
     *       syntax will have their value substituted with the appropriate
     *       system property value.
     *   </li>
     *   <li><i><b>Read the framework's configuration property file.</b></i> This is
     *       a file containing properties used to configure the framework
     *       instance and to pass configuration information into
     *       bundles installed into the framework instance. The configuration
     *       property file is called <tt>config.properties</tt> by default
     *       and is located in the <tt>conf/</tt> directory of the Felix
     *       installation directory, which is the parent directory of the
     *       directory containing the <tt>felix.jar</tt> file. It is possible
     *       to use a different location for the property file by specifying
     *       the desired URL using the <tt>felix.config.properties</tt>
     *       system property; this should be set using the <tt>-D</tt> syntax
     *       when executing the JVM. If the <tt>config.properties</tt> file
     *       cannot be found, then default values are used for all configuration
     *       properties. Refer to the
     *       <a href="Felix.html#Felix(java.util.Map)"><tt>Felix</tt></a>
     *       constructor documentation for more information on framework
     *       configuration properties.
     *   </li>
     *   <li><i><b>Perform system property variable substitution on configuration
     *       properties.</b></i> Any configuration properties whose value adheres to
     *       <tt>${&lt;system-prop-name&gt;}</tt> syntax will have their value
     *       substituted with the appropriate system property value.
     *   </li>
     *   <li><i><b>Copy configuration properties specified as system properties
     *       into the set of configuration properties.</b></i> Even though the
     *       Felix framework does not consult system properties for configuration
     *       information, sometimes it is convenient to specify them on the command
     *       line when launching Felix. To make this possible, the Felix launcher
     *       copies any configuration properties specified as system properties
     *       into the set of configuration properties passed into Felix.
     *   </li>
     *   <li><i><b>Creates and starts a framework instance.</b></i> The configuration
     *       properties are passed into the Felix constructor and the {{Felix.start()}}
     *       method is called to start the framework.
     *   </li>
     * </ol>
     * <p>
     * It should be noted that simply starting an instance of the framework is not
     * enough to create an interactive session with it. It is necessary to install
     * and start bundles that provide a some means to interact with the framework;
     * this is generally done by specifying an "auto-start" property in the
     * configuration property file. If no bundles providing a means to interact
     * with the framework are installed or if the configuration property
     * file cannot be found, the framework will appear to be hung or deadlocked.
     * This is not the case, it is executing correctly, there is just no way to
     * interact with it. The default launcher provides two configuration properties
     * to help you automatically install and/or start bundles, which are:
     * </p>
     * <ul>
     *   <li><tt>felix.auto.install.&lt;n&gt;</tt> - Space-delimited list of
     *       bundle URLs to automatically install into start level <tt>n</tt> when
     *       the framework is started. Append a specific start level to this
     *       property name to assign the bundles' start level
     *       (e.g., <tt>felix.auto.install.2</tt>); otherwise, bundles are
     *       installed into the default bundle start level.
     *   </li>
     *   <li><tt>felix.auto.start.&lt;n&gt;</tt> - Space-delimited list of
     *       bundle URLs to automatically install and start into start level
     *       <tt>n</tt> when the framework is started. Append a
     *       specific start level to this property name to assign the
     *       bundles' start level(e.g., <tt>felix.auto.start.2</tt>); otherwise,
     *       bundles are installed into the default bundle start level.
     *   </li>
     * </ul>
     * <p>
     * These properties should be specified in the <tt>config.properties</tt>
     * so that they can be processed by the launcher during the framework
     * startup process.
     * </p>
     * @param argv Accepts a single argument, which is the path to use as the
     *        framework's bundle cache.
     * @throws Exception If an error occurs.
    **/
    public static void main(String[] args) throws Exception
    {
        // We support at most one argument, which is the bundle
        // cache directory.
        if (args.length > 1)
        {
            System.out.println("Usage: [<bundle-cache-dir>]");
            System.exit(0);
        }

        // Load system properties.
        Main.loadSystemProperties();

        // Read configuration properties.
        Properties configProps = Main.loadConfigProperties();
        // If no configuration properties were found, then create
        // an empty properties object.
        if (configProps == null)
        {
            System.err.println("No " + CONFIG_PROPERTIES_FILE_VALUE + " found.");
            configProps = new Properties();
        }

        // Copy framework properties from the system properties.
        Main.copySystemProperties(configProps);

        // If there is a passed in bundle cache directory, then
        // that overwrites anything in the config file.
        if (args.length > 0)
        {
            configProps.setProperty(Constants.FRAMEWORK_STORAGE, args[0]);
        }

        // Create a list for custom framework activators and
        // add an instance of the auto-activator it for processing
        // auto-install and auto-start properties. Add this list
        // to the configuration properties.
        List list = new ArrayList();
        list.add(new AutoActivator(configProps));
        configProps.put(FelixConstants.SYSTEMBUNDLE_ACTIVATORS_PROP, list);

        // Print welcome banner.
        System.out.println("\nWelcome to Felix.");
        System.out.println("=================\n");

        try
        {
            // Create an instance and start the framework.
            m_felix = new Felix(configProps);
            m_felix.start();
            // Wait for framework to stop to exit the VM.
            m_felix.waitForStop(0);
            System.exit(0);
        }
        catch (Exception ex)
        {
            System.err.println("Could not create framework: " + ex);
            ex.printStackTrace();
            System.exit(-1);
        }
    }

    /**
     * <p>
     * Loads the properties in the system property file associated with the
     * framework installation into <tt>System.setProperty()</tt>. These properties
     * are not directly used by the framework in anyway. By default, the system
     * property file is located in the <tt>conf/</tt> directory of the Felix
     * installation directory and is called "<tt>system.properties</tt>". The
     * installation directory of Felix is assumed to be the parent directory of
     * the <tt>felix.jar</tt> file as found on the system class path property.
     * The precise file from which to load system properties can be set by
     * initializing the "<tt>felix.system.properties</tt>" system property to an
     * arbitrary URL.
     * </p>
    **/
    public static void loadSystemProperties()
    {
        // The system properties file is either specified by a system
        // property or it is in the same directory as the Felix JAR file.
        // Try to load it from one of these places.

        // See if the property URL was specified as a property.
        URL propURL = null;
        String custom = System.getProperty(SYSTEM_PROPERTIES_PROP);
        if (custom != null)
        {
            try
            {
                propURL = new URL(custom);
            }
            catch (MalformedURLException ex)
            {
                System.err.print("Main: " + ex);
                return;
            }
        }
        else
        {
            // Determine where the configuration directory is by figuring
            // out where felix.jar is located on the system class path.
            File confDir = null;
            String classpath = System.getProperty("java.class.path");
            int index = classpath.toLowerCase().indexOf("felix.jar");
            int start = classpath.lastIndexOf(File.pathSeparator, index) + 1;
            if (index >= start)
            {
                // Get the path of the felix.jar file.
                String jarLocation = classpath.substring(start, index);
                // Calculate the conf directory based on the parent
                // directory of the felix.jar directory.
                confDir = new File(
                    new File(new File(jarLocation).getAbsolutePath()).getParent(),
                    CONFIG_DIRECTORY);
            }
            else
            {
                // Can't figure it out so use the current directory as default.
                confDir = new File(System.getProperty("user.dir"), CONFIG_DIRECTORY);
            }

            try
            {
                propURL = new File(confDir, SYSTEM_PROPERTIES_FILE_VALUE).toURL();
            }
            catch (MalformedURLException ex)
            {
                System.err.print("Main: " + ex);
                return;
            }
        }

        // Read the properties file.
        Properties props = new Properties();
        InputStream is = null;
        try
        {
            is = propURL.openConnection().getInputStream();
            props.load(is);
            is.close();
        }
        catch (FileNotFoundException ex)
        {
            // Ignore file not found.
        }
        catch (Exception ex)
        {
            System.err.println(
                "Main: Error loading system properties from " + propURL);
            System.err.println("Main: " + ex);
            try
            {
                if (is != null) is.close();
            }
            catch (IOException ex2)
            {
                // Nothing we can do.
            }
            return;
        }

        // Perform variable substitution on specified properties.
        for (Enumeration e = props.propertyNames(); e.hasMoreElements(); )
        {
            String name = (String) e.nextElement();
            System.setProperty(name,
                Util.substVars(props.getProperty(name), name, null, null));
        }
    }

    /**
     * <p>
     * Loads the configuration properties in the configuration property file
     * associated with the framework installation; these properties
     * are accessible to the framework and to bundles and are intended
     * for configuration purposes. By default, the configuration property
     * file is located in the <tt>conf/</tt> directory of the Felix
     * installation directory and is called "<tt>config.properties</tt>".
     * The installation directory of Felix is assumed to be the parent
     * directory of the <tt>felix.jar</tt> file as found on the system class
     * path property. The precise file from which to load configuration
     * properties can be set by initializing the "<tt>felix.config.properties</tt>"
     * system property to an arbitrary URL.
     * </p>
     * @return A <tt>Properties</tt> instance or <tt>null</tt> if there was an error.
    **/
    public static Properties loadConfigProperties()
    {
        // The config properties file is either specified by a system
        // property or it is in the conf/ directory of the Felix
        // installation directory.  Try to load it from one of these
        // places.

        // See if the property URL was specified as a property.
        URL propURL = null;
        String custom = System.getProperty(CONFIG_PROPERTIES_PROP);
        if (custom != null)
        {
            try
            {
                propURL = new URL(custom);
            }
            catch (MalformedURLException ex)
            {
                System.err.print("Main: " + ex);
                return null;
            }
        }
        else
        {
            // Determine where the configuration directory is by figuring
            // out where felix.jar is located on the system class path.
            File confDir = null;
            String classpath = System.getProperty("java.class.path");
            int index = classpath.toLowerCase().indexOf("felix.jar");
            int start = classpath.lastIndexOf(File.pathSeparator, index) + 1;
            if (index >= start)
            {
                // Get the path of the felix.jar file.
                String jarLocation = classpath.substring(start, index);
                // Calculate the conf directory based on the parent
                // directory of the felix.jar directory.
                confDir = new File(
                    new File(new File(jarLocation).getAbsolutePath()).getParent(),
                    CONFIG_DIRECTORY);
            }
            else
            {
                // Can't figure it out so use the current directory as default.
                confDir = new File(System.getProperty("user.dir"), CONFIG_DIRECTORY);
            }

            try
            {
                propURL = new File(confDir, CONFIG_PROPERTIES_FILE_VALUE).toURL();
            }
            catch (MalformedURLException ex)
            {
                System.err.print("Main: " + ex);
                return null;
            }
        }

        // Read the properties file.
        Properties props = new Properties();
        InputStream is = null;
        try
        {
            // Try to load config.properties.
            is = propURL.openConnection().getInputStream();
            props.load(is);
            is.close();
        }
        catch (Exception ex)
        {
            // Try to close input stream if we have one.
            try
            {
                if (is != null) is.close();
            }
            catch (IOException ex2)
            {
                // Nothing we can do.
            }

            return null;
        }

        // Perform variable substitution for system properties.
        for (Enumeration e = props.propertyNames(); e.hasMoreElements(); )
        {
            String name = (String) e.nextElement();
            props.setProperty(name,
                Util.substVars(props.getProperty(name), name, null, props));
        }

        return props;
    }

    public static void copySystemProperties(Properties configProps)
    {
        for (Enumeration e = System.getProperties().propertyNames();
             e.hasMoreElements(); )
        {
            String key = (String) e.nextElement();
            if (key.startsWith("felix.") || key.startsWith("org.osgi.framework."))
            {
                configProps.setProperty(key, System.getProperty(key));
            }
        }
    }
}