util/src/main/java/org/apache/karaf/util/InterpolationHelper.java - karaf - 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.karaf.util;

 import java.util.HashMap;
 import java.util.Map;

 import org.osgi.framework.BundleContext;

 /**
  * Enhancement of the standard <code>Properties</code>
  * managing the maintain of comments, etc.
  */
 public class InterpolationHelper {

     private InterpolationHelper() {
     }

     private static final char ESCAPE_CHAR = '\\';
     private static final String DELIM_START = "${";
     private static final String DELIM_STOP = "}";


     /**
      * Callback for substitution
      */
     public interface SubstitutionCallback {

         public String getValue(String key);

     }

     /**
      * Perform substitution on a property set
      *
      * @param properties the property set to perform substitution on
      */
     public static void performSubstitution(Map<String, String> properties) {
         performSubstitution(properties, (BundleContext) null);
     }

     /**
      * Perform substitution on a property set
      *
      * @param properties the property set to perform substitution on
      */
     public static void performSubstitution(Map<String, String> properties, final BundleContext context) {
         performSubstitution(properties, new SubstitutionCallback() {
             public String getValue(String key) {
                 String value = null;
                 if (context != null) {
                     value = context.getProperty(key);
                 }
                 if (value == null) {
                     value = System.getProperty(value, "");
                 }
                 return value;
             }
         });
     }

     /**
      * Perform substitution on a property set
      *
      * @param properties the property set to perform substitution on
      */
     public static void performSubstitution(Map<String, String> properties, SubstitutionCallback callback) {
         for (String name : properties.keySet()) {
             String value = properties.get(name);
             properties.put(name, substVars(value, name, null, properties, callback));
         }
     }


     /**
      * <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.
      * @param callback    the callback to obtain substitution values
      * @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.
      */
     public static String substVars(String val,
                                    String currentKey,
                                    Map<String, String> cycleMap,
                                    Map<String, String> configProps,
                                    SubstitutionCallback callback)
             throws IllegalArgumentException {
         if (cycleMap == null) {
             cycleMap = new HashMap<String, String>();
         }

         // 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);
         while (stopDelim > 0 && val.charAt(stopDelim - 1) == ESCAPE_CHAR) {
             stopDelim = val.indexOf(DELIM_STOP, stopDelim + 1);
         }

         // 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.
         if ((startDelim < 0) || (stopDelim < 0)) {
             return unescape(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 = (String) ((configProps != null) ? configProps.get(variable) : null);
         if (substValue == null) {
             if (variable.length() <= 0) {
                 substValue = "";
             } else {
                 if (callback != null) {
                     substValue = callback.getValue(variable);
                 }
                 if (substValue == null) {
                     substValue = System.getProperty(variable, "");
                 }
             }
         }

         // 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, callback);

         // Remove escape characters preceding {, } and \
         val = unescape(val);

         // Return the value.
         return val;
     }

     private static String unescape(String val) {
         int escape = val.indexOf(ESCAPE_CHAR);
         while (escape >= 0 && escape < val.length() - 1) {
             char c = val.charAt(escape + 1);
             if (c == '{' || c == '}' || c == ESCAPE_CHAR) {
                 val = val.substring(0, escape) + val.substring(escape + 1);
             }
             escape = val.indexOf(ESCAPE_CHAR, escape + 1);
         }
         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.karaf.util;

	import java.util.HashMap;
	import java.util.Map;

	import org.osgi.framework.BundleContext;

	/**
	* Enhancement of the standard <code>Properties</code>
	* managing the maintain of comments, etc.
	*/
	public class InterpolationHelper {

	private InterpolationHelper() {
	}

	private static final char ESCAPE_CHAR = '\\';
	private static final String DELIM_START = "${";
	private static final String DELIM_STOP = "}";


	/**
	* Callback for substitution
	*/
	public interface SubstitutionCallback {

	public String getValue(String key);

	}

	/**
	* Perform substitution on a property set
	*
	* @param properties the property set to perform substitution on
	*/
	public static void performSubstitution(Map<String, String> properties) {
	performSubstitution(properties, (BundleContext) null);
	}

	/**
	* Perform substitution on a property set
	*
	* @param properties the property set to perform substitution on
	*/
	public static void performSubstitution(Map<String, String> properties, final BundleContext context) {
	performSubstitution(properties, new SubstitutionCallback() {
	public String getValue(String key) {
	String value = null;
	if (context != null) {
	value = context.getProperty(key);
	}
	if (value == null) {
	value = System.getProperty(value, "");
	}
	return value;
	}
	});
	}

	/**
	* Perform substitution on a property set
	*
	* @param properties the property set to perform substitution on
	*/
	public static void performSubstitution(Map<String, String> properties, SubstitutionCallback callback) {
	for (String name : properties.keySet()) {
	String value = properties.get(name);
	properties.put(name, substVars(value, name, null, properties, callback));
	}
	}


	/**
	* <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.
	* @param callback the callback to obtain substitution values
	* @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.
	*/
	public static String substVars(String val,
	String currentKey,
	Map<String, String> cycleMap,
	Map<String, String> configProps,
	SubstitutionCallback callback)
	throws IllegalArgumentException {
	if (cycleMap == null) {
	cycleMap = new HashMap<String, String>();
	}

	// 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);
	while (stopDelim > 0 && val.charAt(stopDelim - 1) == ESCAPE_CHAR) {
	stopDelim = val.indexOf(DELIM_STOP, stopDelim + 1);
	}

	// 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.
	if ((startDelim < 0) \|\| (stopDelim < 0)) {
	return unescape(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 = (String) ((configProps != null) ? configProps.get(variable) : null);
	if (substValue == null) {
	if (variable.length() <= 0) {
	substValue = "";
	} else {
	if (callback != null) {
	substValue = callback.getValue(variable);
	}
	if (substValue == null) {
	substValue = System.getProperty(variable, "");
	}
	}
	}

	// 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, callback);

	// Remove escape characters preceding {, } and \
	val = unescape(val);

	// Return the value.
	return val;
	}

	private static String unescape(String val) {
	int escape = val.indexOf(ESCAPE_CHAR);
	while (escape >= 0 && escape < val.length() - 1) {
	char c = val.charAt(escape + 1);
	if (c == '{' \|\| c == '}' \|\| c == ESCAPE_CHAR) {
	val = val.substring(0, escape) + val.substring(escape + 1);
	}
	escape = val.indexOf(ESCAPE_CHAR, escape + 1);
	}
	return val;
	}

	}