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/*
*
* Copyright (c) 2006 The Apache Software Foundation
*
* Licensed 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.qpid.configuration;
import java.util.ArrayList;
import java.util.Iterator;
/**
* Based on code in Apache Ant, this utility class handles property expansion. This
* is most useful in config files and so on.
*/
public class PropertyUtils
{
/**
* Replaces <code>${xxx}</code> style constructions in the given value
* with the string value of the corresponding data types. Replaces only system
* properties
*
* @param value The string to be scanned for property references.
* May be <code>null</code>, in which case this
* method returns immediately with no effect.
* @return the original string with the properties replaced, or
* <code>null</code> if the original string is <code>null</code>.
* @throws PropertyException if the string contains an opening
* <code>${</code> without a closing
* <code>}</code>
*/
public static String replaceProperties(String value) throws PropertyException
{
if (value == null)
{
return null;
}
ArrayList<String> fragments = new ArrayList<String>();
ArrayList<String> propertyRefs = new ArrayList<String>();
parsePropertyString(value, fragments, propertyRefs);
StringBuffer sb = new StringBuffer();
Iterator j = propertyRefs.iterator();
for (String fragment : fragments)
{
if (fragment == null)
{
String propertyName = (String) j.next();
// try to get it from the project or keys
// Backward compatibility
String replacement = System.getProperty(propertyName);
if (replacement == null)
{
throw new PropertyException("Property ${" + propertyName +
"} has not been set");
}
fragment = replacement;
}
sb.append(fragment);
}
return sb.toString();
}
/**
* Default parsing method. Parses the supplied value for properties which are specified
* using ${foo} syntax. $X is left as is, and $$ specifies a single $.
* @param value the property string to parse
* @param fragments is populated with the string fragments. A null means "insert a
* property value here. The number of nulls in the list when populated is equal to the
* size of the propertyRefs list
* @param propertyRefs populated with the property names to be added into the final
* String.
*/
private static void parsePropertyString(String value, ArrayList<String> fragments,
ArrayList<String> propertyRefs)
throws PropertyException
{
int prev = 0;
int pos;
//search for the next instance of $ from the 'prev' position
while ((pos = value.indexOf("$", prev)) >= 0)
{
//if there was any text before this, add it as a fragment
if (pos > 0)
{
fragments.add(value.substring(prev, pos));
}
//if we are at the end of the string, we tack on a $
//then move past it
if (pos == (value.length() - 1))
{
fragments.add("$");
prev = pos + 1;
}
else if (value.charAt(pos + 1) != '{')
{
//peek ahead to see if the next char is a property or not
//not a property: insert the char as a literal
if (value.charAt(pos + 1) == '$')
{
// two $ map to one $
fragments.add("$");
prev = pos + 2;
}
else
{
// $X maps to $X for all values of X!='$'
fragments.add(value.substring(pos, pos + 2));
prev = pos + 2;
}
}
else
{
// property found, extract its name or bail on a typo
int endName = value.indexOf('}', pos);
if (endName < 0)
{
throw new PropertyException("Syntax error in property: " +
value);
}
String propertyName = value.substring(pos + 2, endName);
fragments.add(null);
propertyRefs.add(propertyName);
prev = endName + 1;
}
}
//no more $ signs found
//if there is any tail to the file, append it
if (prev < value.length())
{
fragments.add(value.substring(prev));
}
}
}
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