Support property references in XML files

src/gov/nasa/worldwind/Configuration.java

@@ -256,6 +256,11 @@ public static synchronized String getStringValue(String key, String defaultValue
     public static synchronized String getStringValue(String key)
     {
         Object o = getInstance().properties.getProperty(key);
+
+		if( o != null && o instanceof String )
+        {
+            o = WWUtil.replacePropertyReferences((String)o);            
+        }
         return o != null ? o.toString() : null;
     }
 

src/gov/nasa/worldwind/util/WWUtil.java

@@ -6,6 +6,7 @@
 
 package gov.nasa.worldwind.util;
 
+import gov.nasa.worldwind.Configuration;
 import gov.nasa.worldwind.avlist.*;
 import gov.nasa.worldwind.geom.*;
 import gov.nasa.worldwind.geom.coords.UTMCoord;
@@ -14,6 +15,7 @@
 import java.lang.reflect.*;
 import java.nio.*;
 import java.text.*;
+import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 /**
@@ -22,6 +24,9 @@
  */
 public class WWUtil
 {
+    static final String JAVA_CONFIG_VARIABLE = "\\$\\{([-a-zA-Z0-9._]+)\\}";
+
+    static final Pattern propPattern = Pattern.compile(JAVA_CONFIG_VARIABLE);
     /**
      * Converts a specified string to an integer value. Returns null if the string cannot be converted.
      *
@@ -1270,4 +1275,45 @@ public static void generateTriStripNormals(FloatBuffer vertices, IntBuffer indic
             normals.put(i3 + 2, (float) n3.z);
         }
     }
+
+	 /**
+     * Replace all instances of ${....} with the corresponding
+     * property defined in the {@link #org.nasa.worldwind.Configuration()}
+     * 
+     * @param in string containing ${} to be replaced
+     * 
+     * @return result of in after ${} replacement
+     */
+	public final static String replacePropertyReferences(String in)
+	{
+	    if(in == null || in.indexOf("${") == -1) return in;
+	    String result = in;
+
+	    Matcher matcher = propPattern.matcher(result);
+	    StringBuffer buf = new StringBuffer();
+	    while (matcher.find())
+	    {
+	        String replaceStr = matcher.group(1);
+
+	        //Since the Configuration.getStringValue also uses this routine
+	        //this will resolve any nested properties references
+	        String prop = Configuration.getStringValue(replaceStr);   
+
+	        //if it isn't in our Configuration, check if it is a system property
+	        if (prop == null )
+	        	//Make sure we expand any properties references in the property
+	            prop = replacePropertyReferences(System.getProperty(replaceStr));
+	        if( prop == null )
+	        {
+	        	Logging.logger().warning(String.format("Failed to find property '%s' for '%s'\n", replaceStr, in));	        	
+	        }
+	        else
+	        {
+				matcher.appendReplacement(buf, prop);
+	        } 	        	    
+	    }
+	    matcher.appendTail(buf);
+	    result = buf.toString();
+	    return result;
+	}
 }

src/gov/nasa/worldwind/util/WWXML.java

@@ -816,7 +816,8 @@ public static String getText(Element context, String path, XPath xpath)
 
         try
         {
-            return xpath.evaluate(path, context);
+            String val = xpath.evaluate(path, context);
+			return WWUtil.replacePropertyReferences(val);
         }
         catch (XPathExpressionException e)
         {

test/gov/nasa/worldwind/util/WWUtilTest.java

@@ -6,10 +6,20 @@
 
 package gov.nasa.worldwind.util;
 
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import gov.nasa.worldwind.Configuration;
+import gov.nasa.worldwind.util.WWUtil;
 import junit.framework.TestCase;
+
 import org.junit.Test;
 
+import java.io.ByteArrayOutputStream;
 import java.util.*;
+import java.util.logging.Handler;
+import java.util.logging.Logger;
+import java.util.logging.SimpleFormatter;
+import java.util.logging.StreamHandler;
 
 /**
  * Unit tests for {@link WWUtil}.
@@ -50,4 +60,43 @@ public void testParseTimeString()
         time = WWUtil.parseTimeString("invalid time");
         TestCase.assertNull(time);
     }
+
+    @Test
+    public void testReplacePropertyReferences()
+    {
+    	//Test that we can resolve nested property references 
+    	//and properties defined at the system level
+    	Configuration.setValue("a", "I am a");
+        System.setProperty("b", "${a}");
+    	Configuration.setValue("c", "${a}, ${b}");
+        String expanded = WWUtil.replacePropertyReferences("Prefix_${c}_Suffix");
+        TestCase.assertEquals("Prefix_I am a, I am a_Suffix", expanded);
+    }    
+
+    @Test
+    public void testReplacePropertyReferencesLogging()
+    {
+
+        //Test that we get a log message when the property doesn't exist
+        Logger logger = Logging.logger();
+
+        SimpleFormatter formatter = new SimpleFormatter();
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        Handler handler = new StreamHandler(out, formatter);
+        logger.addHandler(handler);
+        try
+        {
+        	WWUtil.replacePropertyReferences("${property.does.not.exist}");
+        	handler.flush();
+            String logMsg = out.toString();
+
+            assertNotNull(logMsg);
+            assertTrue(logMsg.contains("Failed to find property 'property.does.not.exist' for '${property.does.not.exist}'"));
+        }
+        finally
+        {
+        	logger.removeHandler(handler);
+        }
+    }
+
 }