org.apache.ace.configurator/src/org/apache/ace/configurator/Configurator.java - ace - Git at Google

 /*
  * 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.ace.configurator;

 import java.io.File;
 import java.io.FileFilter;
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Collections;
 import java.util.Dictionary;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Hashtable;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 import java.util.Set;

 import org.osgi.framework.BundleContext;
 import org.osgi.framework.InvalidSyntaxException;
 import org.osgi.service.cm.Configuration;
 import org.osgi.service.cm.ConfigurationAdmin;
 import org.osgi.service.log.LogService;

 /**
  * Configures bundles managed by the <code>ConfigurationAdmin</code>. This Configurator uses text files as configuration
  * files containing properties. When a configuration file is added, the properties are being read and added. If the
  * config file is removed, the properties are removed as well.
  * <p>
  * The configuration files should be stored in the configuration directory (often the 'conf' directory) of the OSGi
  * framework and should have the format: &lt;pid&gt;.cfg
  * <p>
  * Note: this Configurator is based upon the principle in the FileInstall bundle Peter Kriens wrote. (see
  * http://www.aqute.biz/Code/FileInstall for more information)
  */
 public class Configurator implements Runnable {
     private static final String DELIM_START = "${";
     private static final String DELIM_STOP = "}";

     private static final FileFilter FILENAME_FILTER = new FileFilter() {
         public boolean accept(File file) {
             return !file.isHidden() && (file.getName().endsWith(".cfg") || file.isDirectory());
         }
     };

     private static final String FACTORY_INSTANCE_KEY = "factory.instance.pid";

     private volatile LogService m_log; /* injected by dependency manager */
     private volatile ConfigurationAdmin m_configAdmin; /* injected by dependency manager */
     private volatile BundleContext m_context; /* injected by dependency manager */

     private final File m_configDir;
     private final long m_pollInterval;
     private final Map<String, Long> m_checksums = new HashMap<>();
     private final Map<String, Map<String, Long>> m_foundFactories = new HashMap<>();
     private final boolean m_reconfig;

     private Thread m_configThread;

     /**
      * Instantiates a new configurator.
      *
      * @param dir
      *            The directory to watch.
      * @param pollInterval
      *            The poll iterval in ms.
      * @param reconfig
      *            Whether or not to use reconfiguration: if <code>false</code>, existing configuration values will not
      *            be overwritten, only new values (for a given pid) will be added.
      */
     public Configurator(File dir, long pollInterval, boolean reconfig) {
         if ((dir == null) || !dir.isDirectory() || (pollInterval < 0)) {
             throw new IllegalArgumentException("Bad arguments; either not an existing directory or an invalid interval.");
         }
         m_configDir = dir;
         m_pollInterval = pollInterval;
         m_reconfig = reconfig;
     }

     /**
      * Starts the Configuration timer.
      */
     synchronized void start() {
         if (m_configThread == null) {
             m_configThread = new Thread(this, "Apache ACE Configurator");
         }
         m_configThread.setDaemon(true);
         m_configThread.start();
     }

     /**
      * Stops the Configuration timer.
      *
      * @throws InterruptedException
      */
     synchronized void stop() throws InterruptedException {
         // Join in stop to prevent race condition, careful with bundle location setting to null
         m_configThread.interrupt();
         m_configThread.join();
         m_configThread = null;
         m_checksums.clear();
     }

     /**
      * Starts the actual Timer task, and calls the configurator to make sure the configurations are performed. Checking
      * whether a new configuration is present, will be done with an interval that can be defined via a system property.
      */
     public void run() {
         try {
             while (!Thread.interrupted()) {
                 doConfigs();
                 Thread.sleep(m_pollInterval);
             }
         }
         catch (InterruptedException ex) {
             // We are requested to stop.
         }
     }

     /**
      * Enables the actual configuring of OSGi ManagedServices. It makes sure all new configurations are added, changed
      * configurations are updated, and old configurations are removed. Configurations are updated when the timestamp or
      * the size of the new configuration has changed.
      */
     private void doConfigs() {
         Set<String> pids = new HashSet<>(m_checksums.keySet());

         File[] files = m_configDir.listFiles(FILENAME_FILTER);
         for (int i = 0; (files != null) && (i < files.length); i++) {
             File file = files[i];
             String pid = parsePid(file);

             if (file.isDirectory()) {
                 doFactoryConfigs(pid, file.listFiles(FILENAME_FILTER));
             }
             else {
                 Long newChecksum = new Long(file.lastModified() ^ file.length());
                 Long oldChecksum = (Long) m_checksums.get(pid); // may be null, intended
                 if (!newChecksum.equals(oldChecksum)) {
                     m_checksums.put(pid, newChecksum);
                     processConfigFile(file, null);
                 }
                 pids.remove(pid);
             }
         }
         for (String pid : pids) {
             deleteConfig(pid, null);
             m_checksums.remove(pid);
         }
     }

     private void doFactoryConfigs(String factoryPid, File[] newInstances) {
         if (!m_foundFactories.containsKey(factoryPid)) {
             m_foundFactories.put(factoryPid, new HashMap<String, Long>());
         }
         Map<String, Long> instances = m_foundFactories.get(factoryPid);
         Set<String> instancesPids = new HashSet<>(instances.keySet());

         for (int j = 0; j < newInstances.length; j++) {
             File instanceConfigFile = newInstances[j];
             String instancePid = parsePid(instanceConfigFile);

             Long newChecksum = new Long(instanceConfigFile.lastModified() ^ instanceConfigFile.length());
             Long oldChecksum = (Long) instances.get(instancePid);
             if (!newChecksum.equals(oldChecksum)) {
                 instances.put(instancePid, newChecksum);
                 processConfigFile(instanceConfigFile, factoryPid);
             }
             instancesPids.remove(instancePid);
         }

         for (String instancePid : instancesPids) {
             deleteConfig(instancePid, factoryPid);
             instances.remove(instancePid);
         }
     }

     /**
      * Sets the Configuration and calls update() to do the actual configuration on the ManagedService. If and only if
      * the configuration did not exist before or has changed. A configuration has changed if the length or the
      * lastModified date has changed.
      */
     private void processConfigFile(File configFile, String factoryPid) {
         try (InputStream in  = new FileInputStream(configFile)) {
             Properties properties = new Properties();
             properties.load(in);

             String pid = parsePid(configFile);
             properties = substVars(properties);
             configure(pid, factoryPid, properties);
         }
         catch (IOException ex) {
             m_log.log(LogService.LOG_ERROR, "Unable to read configuration from file: " + configFile.getAbsolutePath(), ex);
         }
     }

     private void configure(String pid, String factoryPid, Properties properties) {
         try {
             Configuration config = getConfiguration(pid, factoryPid);

             Dictionary<String, Object> props = config.getProperties();
             if (props == null) {
                 props = new Hashtable<>();
             }

             List<String> curKeys = Collections.list(props.keys());
             for (Object key : properties.keySet()) {
                 if (curKeys.contains(key) && !m_reconfig) {
                     m_log.log(LogService.LOG_DEBUG, "Using previously configured value for bundle=" + pid + " key=" + key);
                 } else {
                     props.put((String) key, properties.get(key));
                 }
             }

             if (factoryPid != null) {
                 props.put(FACTORY_INSTANCE_KEY, factoryPid + "_" + pid);
             }

             config.update(props);
             m_log.log(LogService.LOG_DEBUG, "Updated configuration for pid '" + pid + "' (" + props + ")");
         }
         catch (IOException ex) {
             m_log.log(LogService.LOG_ERROR, "Unable to update configuration for pid '" + pid + "'", ex);
         }
     }

     private Configuration getConfiguration(String pid, String factoryPid) throws IOException {
         if (factoryPid != null) {
             Configuration[] configs = null;
             try {
                 configs = m_configAdmin.listConfigurations("(" + FACTORY_INSTANCE_KEY + "=" + factoryPid + "_" + pid + ")");
             }
             catch (InvalidSyntaxException e) {
                 m_log.log(LogService.LOG_ERROR, "Exception during lookup of configuration of managed service factory instance '" + pid + "'", e);
             }
             if ((configs == null) || (configs.length == 0)) {
                 return m_configAdmin.createFactoryConfiguration(factoryPid, null);
             }
             else {
                 return configs[0];
             }
         }
         else {
             return m_configAdmin.getConfiguration(pid, null);
         }
     }

     /**
      * Removes a configuration from ConfigAdmin.
      */
     protected void deleteConfig(String pid, String factoryPid) {
         try {
             Configuration config = getConfiguration(pid, factoryPid);
             config.delete();
             m_log.log(LogService.LOG_DEBUG, "Removed configuration for pid '" + pid + "'");
         }
         catch (Exception e) {
             m_log.log(LogService.LOG_ERROR, "Unable to remove configuration for pid '" + pid + "'", e);
         }
     }

     /**
      * Remove the config extension (.cfg) and return the resulting String.
      */
     protected String parsePid(File file) {
         String name = file.getName();
         if (file.isDirectory()) {
             // factory pid
             return name;
         }
         else {
             return name.substring(0, name.length() - 4);
         }
     }

     /**
      * Performs variable substitution for a complete set of properties
      *
      * @see #substVars(String, String, java.util.Map, java.util.Properties)
      * @param properties
      *            Set of properties to apply substitution on.
      * @return Same set of properties with all variables substituted.
      */
     private Properties substVars(Properties properties) {
         for (Map.Entry<Object, Object> entry : properties.entrySet()) {
             String name = (String) entry.getKey();
             String value = (String) entry.getValue();
             properties.setProperty(name, substVars(value, name, null, properties));
         }
         return properties;
     }

     /**
      * <p>
      * This method performs property variable substitution on the specified value. If the specified value contains the
      * syntax <tt>${&lt;prop-name&gt;}</tt>, where <tt>&lt;prop-name&gt;</tt> refers to either a configuration property
      * or a system property, then the corresponding property value is substituted for the variable placeholder. Multiple
      * variable placeholders may exist in the specified value as well as nested variable placeholders, which are
      * substituted from inner most to outer most. Configuration properties override system properties.
      * </p>
      *
      * @param val
      *            The string on which to perform property substitution.
      * @param currentKey
      *            The key of the property being evaluated used to detect cycles.
      * @param cycleMap
      *            Map of variable references used to detect nested cycles.
      * @param configProps
      *            Set of configuration properties.
      * @return The value of the specified string after system property substitution.
      * @throws IllegalArgumentException
      *             If there was a syntax error in the property placeholder syntax or a recursive variable reference.
      */
     private String substVars(String val, String currentKey, Map<String, String> cycleMap, Properties configProps) throws IllegalArgumentException {
         // If there is currently no cycle map, then create
         // one for detecting cycles for this invocation.
         if (cycleMap == null) {
             cycleMap = new HashMap<>();
         }

         // Put the current key in the cycle map.
         cycleMap.put(currentKey, currentKey);

         // Assume we have a value that is something like:
         // "leading ${foo.${bar}} middle ${baz} trailing"

         // Find the first ending '}' variable delimiter, which
         // will correspond to the first deepest nested variable
         // placeholder.
         int stopDelim = val.indexOf(DELIM_STOP);

         // Find the matching starting "${" variable delimiter
         // by looping until we find a start delimiter that is
         // greater than the stop delimiter we have found.
         int startDelim = val.indexOf(DELIM_START);
         while (stopDelim >= 0) {
             int idx = val.indexOf(DELIM_START, startDelim + DELIM_START.length());
             if ((idx < 0) || (idx > stopDelim)) {
                 break;
             }
             else if (idx < stopDelim) {
                 startDelim = idx;
             }
         }

         // If we do not have a start or stop delimiter, then just
         // return the existing value.
         // ACE-401: be liberal to the content, and do not throw an exception in case we see something that resembles a substitution but is in fact nothing...
         if ((startDelim < 0) || (stopDelim < 0) || (startDelim > stopDelim)) {
             return val;
         }

         // At this point, we have found a variable placeholder so
         // we must perform a variable substitution on it.
         // Using the start and stop delimiter indices, extract
         // the first, deepest nested variable placeholder.
         String variable = val.substring(startDelim + DELIM_START.length(), stopDelim);

         // Verify that this is not a recursive variable reference.
         if (cycleMap.get(variable) != null) {
             throw new IllegalArgumentException("recursive variable reference: " + variable);
         }

         // Get the value of the deepest nested variable placeholder.
         // Try to configuration properties first.
         String substValue = (configProps != null) ? configProps.getProperty(variable, null) : null;
         if (substValue == null) {
             // Ignore unknown property values, check whether it is defined as framework or system property...
             substValue = m_context.getProperty(variable);
             if (substValue == null) {
                 // Still not found, then ignore this substitution...
                 return val;
             }
         }

         // Remove the found variable from the cycle map, since
         // it may appear more than once in the value and we don't
         // want such situations to appear as a recursive reference.
         cycleMap.remove(variable);

         // Append the leading characters, the substituted value of
         // the variable, and the trailing characters to get the new
         // value.
         val = val.substring(0, startDelim) + substValue + val.substring(stopDelim + DELIM_STOP.length(), val.length());

         // Now perform substitution again, since there could still
         // be substitutions to make.
         val = substVars(val, currentKey, cycleMap, configProps);

         // Return the value.
         return val;
     }
 }
	/*
	* 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.ace.configurator;

	import java.io.File;
	import java.io.FileFilter;
	import java.io.FileInputStream;
	import java.io.IOException;
	import java.io.InputStream;
	import java.util.Collections;
	import java.util.Dictionary;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.Hashtable;
	import java.util.List;
	import java.util.Map;
	import java.util.Properties;
	import java.util.Set;

	import org.osgi.framework.BundleContext;
	import org.osgi.framework.InvalidSyntaxException;
	import org.osgi.service.cm.Configuration;
	import org.osgi.service.cm.ConfigurationAdmin;
	import org.osgi.service.log.LogService;

	/**
	* Configures bundles managed by the <code>ConfigurationAdmin</code>. This Configurator uses text files as configuration
	* files containing properties. When a configuration file is added, the properties are being read and added. If the
	* config file is removed, the properties are removed as well.
	* <p>
	* The configuration files should be stored in the configuration directory (often the 'conf' directory) of the OSGi
	* framework and should have the format: <pid>.cfg
	* <p>
	* Note: this Configurator is based upon the principle in the FileInstall bundle Peter Kriens wrote. (see
	* http://www.aqute.biz/Code/FileInstall for more information)
	*/
	public class Configurator implements Runnable {
	private static final String DELIM_START = "${";
	private static final String DELIM_STOP = "}";

	private static final FileFilter FILENAME_FILTER = new FileFilter() {
	public boolean accept(File file) {
	return !file.isHidden() && (file.getName().endsWith(".cfg") \|\| file.isDirectory());
	}
	};

	private static final String FACTORY_INSTANCE_KEY = "factory.instance.pid";

	private volatile LogService m_log; /* injected by dependency manager */
	private volatile ConfigurationAdmin m_configAdmin; /* injected by dependency manager */
	private volatile BundleContext m_context; /* injected by dependency manager */

	private final File m_configDir;
	private final long m_pollInterval;
	private final Map<String, Long> m_checksums = new HashMap<>();
	private final Map<String, Map<String, Long>> m_foundFactories = new HashMap<>();
	private final boolean m_reconfig;

	private Thread m_configThread;

	/**
	* Instantiates a new configurator.
	*
	* @param dir
	* The directory to watch.
	* @param pollInterval
	* The poll iterval in ms.
	* @param reconfig
	* Whether or not to use reconfiguration: if <code>false</code>, existing configuration values will not
	* be overwritten, only new values (for a given pid) will be added.
	*/
	public Configurator(File dir, long pollInterval, boolean reconfig) {
	if ((dir == null) \|\| !dir.isDirectory() \|\| (pollInterval < 0)) {
	throw new IllegalArgumentException("Bad arguments; either not an existing directory or an invalid interval.");
	}
	m_configDir = dir;
	m_pollInterval = pollInterval;
	m_reconfig = reconfig;
	}

	/**
	* Starts the Configuration timer.
	*/
	synchronized void start() {
	if (m_configThread == null) {
	m_configThread = new Thread(this, "Apache ACE Configurator");
	}
	m_configThread.setDaemon(true);
	m_configThread.start();
	}

	/**
	* Stops the Configuration timer.
	*
	* @throws InterruptedException
	*/
	synchronized void stop() throws InterruptedException {
	// Join in stop to prevent race condition, careful with bundle location setting to null
	m_configThread.interrupt();
	m_configThread.join();
	m_configThread = null;
	m_checksums.clear();
	}

	/**
	* Starts the actual Timer task, and calls the configurator to make sure the configurations are performed. Checking
	* whether a new configuration is present, will be done with an interval that can be defined via a system property.
	*/
	public void run() {
	try {
	while (!Thread.interrupted()) {
	doConfigs();
	Thread.sleep(m_pollInterval);
	}
	}
	catch (InterruptedException ex) {
	// We are requested to stop.
	}
	}

	/**
	* Enables the actual configuring of OSGi ManagedServices. It makes sure all new configurations are added, changed
	* configurations are updated, and old configurations are removed. Configurations are updated when the timestamp or
	* the size of the new configuration has changed.
	*/
	private void doConfigs() {
	Set<String> pids = new HashSet<>(m_checksums.keySet());

	File[] files = m_configDir.listFiles(FILENAME_FILTER);
	for (int i = 0; (files != null) && (i < files.length); i++) {
	File file = files[i];
	String pid = parsePid(file);

	if (file.isDirectory()) {
	doFactoryConfigs(pid, file.listFiles(FILENAME_FILTER));
	}
	else {
	Long newChecksum = new Long(file.lastModified() ^ file.length());
	Long oldChecksum = (Long) m_checksums.get(pid); // may be null, intended
	if (!newChecksum.equals(oldChecksum)) {
	m_checksums.put(pid, newChecksum);
	processConfigFile(file, null);
	}
	pids.remove(pid);
	}
	}
	for (String pid : pids) {
	deleteConfig(pid, null);
	m_checksums.remove(pid);
	}
	}

	private void doFactoryConfigs(String factoryPid, File[] newInstances) {
	if (!m_foundFactories.containsKey(factoryPid)) {
	m_foundFactories.put(factoryPid, new HashMap<String, Long>());
	}
	Map<String, Long> instances = m_foundFactories.get(factoryPid);
	Set<String> instancesPids = new HashSet<>(instances.keySet());

	for (int j = 0; j < newInstances.length; j++) {
	File instanceConfigFile = newInstances[j];
	String instancePid = parsePid(instanceConfigFile);

	Long newChecksum = new Long(instanceConfigFile.lastModified() ^ instanceConfigFile.length());
	Long oldChecksum = (Long) instances.get(instancePid);
	if (!newChecksum.equals(oldChecksum)) {
	instances.put(instancePid, newChecksum);
	processConfigFile(instanceConfigFile, factoryPid);
	}
	instancesPids.remove(instancePid);
	}

	for (String instancePid : instancesPids) {
	deleteConfig(instancePid, factoryPid);
	instances.remove(instancePid);
	}
	}

	/**
	* Sets the Configuration and calls update() to do the actual configuration on the ManagedService. If and only if
	* the configuration did not exist before or has changed. A configuration has changed if the length or the
	* lastModified date has changed.
	*/
	private void processConfigFile(File configFile, String factoryPid) {
	try (InputStream in = new FileInputStream(configFile)) {
	Properties properties = new Properties();
	properties.load(in);

	String pid = parsePid(configFile);
	properties = substVars(properties);
	configure(pid, factoryPid, properties);
	}
	catch (IOException ex) {
	m_log.log(LogService.LOG_ERROR, "Unable to read configuration from file: " + configFile.getAbsolutePath(), ex);
	}
	}

	private void configure(String pid, String factoryPid, Properties properties) {
	try {
	Configuration config = getConfiguration(pid, factoryPid);

	Dictionary<String, Object> props = config.getProperties();
	if (props == null) {
	props = new Hashtable<>();
	}

	List<String> curKeys = Collections.list(props.keys());
	for (Object key : properties.keySet()) {
	if (curKeys.contains(key) && !m_reconfig) {
	m_log.log(LogService.LOG_DEBUG, "Using previously configured value for bundle=" + pid + " key=" + key);
	} else {
	props.put((String) key, properties.get(key));
	}
	}

	if (factoryPid != null) {
	props.put(FACTORY_INSTANCE_KEY, factoryPid + "_" + pid);
	}

	config.update(props);
	m_log.log(LogService.LOG_DEBUG, "Updated configuration for pid '" + pid + "' (" + props + ")");
	}
	catch (IOException ex) {
	m_log.log(LogService.LOG_ERROR, "Unable to update configuration for pid '" + pid + "'", ex);
	}
	}

	private Configuration getConfiguration(String pid, String factoryPid) throws IOException {
	if (factoryPid != null) {
	Configuration[] configs = null;
	try {
	configs = m_configAdmin.listConfigurations("(" + FACTORY_INSTANCE_KEY + "=" + factoryPid + "_" + pid + ")");
	}
	catch (InvalidSyntaxException e) {
	m_log.log(LogService.LOG_ERROR, "Exception during lookup of configuration of managed service factory instance '" + pid + "'", e);
	}
	if ((configs == null) \|\| (configs.length == 0)) {
	return m_configAdmin.createFactoryConfiguration(factoryPid, null);
	}
	else {
	return configs[0];
	}
	}
	else {
	return m_configAdmin.getConfiguration(pid, null);
	}
	}

	/**
	* Removes a configuration from ConfigAdmin.
	*/
	protected void deleteConfig(String pid, String factoryPid) {
	try {
	Configuration config = getConfiguration(pid, factoryPid);
	config.delete();
	m_log.log(LogService.LOG_DEBUG, "Removed configuration for pid '" + pid + "'");
	}
	catch (Exception e) {
	m_log.log(LogService.LOG_ERROR, "Unable to remove configuration for pid '" + pid + "'", e);
	}
	}

	/**
	* Remove the config extension (.cfg) and return the resulting String.
	*/
	protected String parsePid(File file) {
	String name = file.getName();
	if (file.isDirectory()) {
	// factory pid
	return name;
	}
	else {
	return name.substring(0, name.length() - 4);
	}
	}

	/**
	* Performs variable substitution for a complete set of properties
	*
	* @see #substVars(String, String, java.util.Map, java.util.Properties)
	* @param properties
	* Set of properties to apply substitution on.
	* @return Same set of properties with all variables substituted.
	*/
	private Properties substVars(Properties properties) {
	for (Map.Entry<Object, Object> entry : properties.entrySet()) {
	String name = (String) entry.getKey();
	String value = (String) entry.getValue();
	properties.setProperty(name, substVars(value, name, null, properties));
	}
	return properties;
	}

	/**
	* <p>
	* This method performs property variable substitution on the specified value. If the specified value contains the
	* syntax <tt>${<prop-name>}</tt>, where <tt><prop-name></tt> refers to either a configuration property
	* or a system property, then the corresponding property value is substituted for the variable placeholder. Multiple
	* variable placeholders may exist in the specified value as well as nested variable placeholders, which are
	* substituted from inner most to outer most. Configuration properties override system properties.
	* </p>
	*
	* @param val
	* The string on which to perform property substitution.
	* @param currentKey
	* The key of the property being evaluated used to detect cycles.
	* @param cycleMap
	* Map of variable references used to detect nested cycles.
	* @param configProps
	* Set of configuration properties.
	* @return The value of the specified string after system property substitution.
	* @throws IllegalArgumentException
	* If there was a syntax error in the property placeholder syntax or a recursive variable reference.
	*/
	private String substVars(String val, String currentKey, Map<String, String> cycleMap, Properties configProps) throws IllegalArgumentException {
	// If there is currently no cycle map, then create
	// one for detecting cycles for this invocation.
	if (cycleMap == null) {
	cycleMap = new HashMap<>();
	}

	// Put the current key in the cycle map.
	cycleMap.put(currentKey, currentKey);

	// Assume we have a value that is something like:
	// "leading ${foo.${bar}} middle ${baz} trailing"

	// Find the first ending '}' variable delimiter, which
	// will correspond to the first deepest nested variable
	// placeholder.
	int stopDelim = val.indexOf(DELIM_STOP);

	// Find the matching starting "${" variable delimiter
	// by looping until we find a start delimiter that is
	// greater than the stop delimiter we have found.
	int startDelim = val.indexOf(DELIM_START);
	while (stopDelim >= 0) {
	int idx = val.indexOf(DELIM_START, startDelim + DELIM_START.length());
	if ((idx < 0) \|\| (idx > stopDelim)) {
	break;
	}
	else if (idx < stopDelim) {
	startDelim = idx;
	}
	}

	// If we do not have a start or stop delimiter, then just
	// return the existing value.
	// ACE-401: be liberal to the content, and do not throw an exception in case we see something that resembles a substitution but is in fact nothing...
	if ((startDelim < 0) \|\| (stopDelim < 0) \|\| (startDelim > stopDelim)) {
	return val;
	}

	// At this point, we have found a variable placeholder so
	// we must perform a variable substitution on it.
	// Using the start and stop delimiter indices, extract
	// the first, deepest nested variable placeholder.
	String variable = val.substring(startDelim + DELIM_START.length(), stopDelim);

	// Verify that this is not a recursive variable reference.
	if (cycleMap.get(variable) != null) {
	throw new IllegalArgumentException("recursive variable reference: " + variable);
	}

	// Get the value of the deepest nested variable placeholder.
	// Try to configuration properties first.
	String substValue = (configProps != null) ? configProps.getProperty(variable, null) : null;
	if (substValue == null) {
	// Ignore unknown property values, check whether it is defined as framework or system property...
	substValue = m_context.getProperty(variable);
	if (substValue == null) {
	// Still not found, then ignore this substitution...
	return val;
	}
	}

	// Remove the found variable from the cycle map, since
	// it may appear more than once in the value and we don't
	// want such situations to appear as a recursive reference.
	cycleMap.remove(variable);

	// Append the leading characters, the substituted value of
	// the variable, and the trailing characters to get the new
	// value.
	val = val.substring(0, startDelim) + substValue + val.substring(stopDelim + DELIM_STOP.length(), val.length());

	// Now perform substitution again, since there could still
	// be substitutions to make.
	val = substVars(val, currentKey, cycleMap, configProps);

	// Return the value.
	return val;
	}
	}