Reusing key in properties file

Question

I want to do something like;
file.environment=D
file.name.incoming=${file.environment}this.txt
file.name.outgoing=${file.environment}that.txtI presume this is not possible to do this in java.util.properties. Is there a package that does this? Or should I just override load() and search/replace the values?

Answer 1

* PropertyResolver.java
* Created on 1 December 2006, 09:45
* Copyright (c) Esmond Pitt, 2006, 2008. All rights reserved.
* Permission is hereby granted for non-commercial use provided this copyright notice is preserved.
import java.util.Enumeration;
import java.util.Properties;
import java.util.Stack;
* ResolvedProperties scans a string and substitutes properties named
* by the syntax ${propertyname} by their values.
* Example: ${user.dir} is replaced by Properties.getProperty("user.dir")
* @author Esmond Pitt
* @version $Revision: 3 $
public class ResolvedProperties extends Properties
      * Creates a new instance of ResolvedProperties using System.getProperties.
     public ResolvedProperties()
     public ResolvedProperties(Properties defaults)
          super(defaults);
     @Override
     public String     getProperty(String name)
          String     value = super.getProperty(name);
          return value != null ? resolve(value) : null;
     @Override
     public String     getProperty(String name, String defaultValue)
          // Note that this must call this.getProperty(String name),
          // not the other way around, as that's what the superclass does.
          // Otherwise you get a stack overflow.
          String     value = getProperty(name);
          return value != null ? value : defaultValue;
     public String resolve(String string)
          StringBuffer     sb = new StringBuffer();
          Stack<StringBuffer>     stack = new Stack<StringBuffer>();
          for(int i=0; i < string.length(); i++)
               char     c = string.charAt(i);
               switch (c)
                    case '$':
                         if (i+1 < string.length() && string.charAt(i+1) == '{')
                              stack.push(sb);
                              sb = new StringBuffer();
                              i++;
                         break;
                    case '}':
                         if (stack.isEmpty())
                              throw new IllegalArgumentException("unexpected '}'");
                         String     name = sb.toString();
                         sb = stack.pop();
                         sb.append(super.getProperty(name, null));
                         break;
                    default:
                         sb.append(c);
                         break;
          if (!stack.isEmpty())
               throw new IllegalArgumentException("expected '}'");
          return sb.toString();
     public static void     main(String[] args)
          ResolvedProperties     pr = new ResolvedProperties();
          pr.setProperty("first.name", "Esmond");
          pr.setProperty("surname", "Pitt");
          pr.setProperty("degrees", "B.A.");
          pr.setProperty("memberships", "MIEEE FACS");
          pr.setProperty("FullName", "${first.name} ${surname} ${degrees} ${memberships}");
          String     s = pr.getProperty("FullName");
          System.out.println(s);
}