Added loadGroupURL to STGroup and URL constructor to STGroupFile

- Changes necessary to support classpath resources in a variety of
different deployment scenarios

See Antlr4 PR: antlr/antlr4#2280

src/org/stringtemplate/v4/STGroup.java

@@ -626,23 +626,32 @@ protected void importTemplates(STGroup g, boolean clearOnUnload) {
 
 	public List<STGroup> getImportedGroups() { return imports; }
 
-	/** Load a group file with full path {@code fileName}; it's relative to root by {@code prefix}. */
-	public void loadGroupFile(String prefix, String fileName) {
-		if ( verbose ) System.out.println(this.getClass().getSimpleName()+
-										  ".loadGroupFile(group-file-prefix="+prefix+", fileName="+fileName+")");
+	public void loadGroupURL(String prefix, URL url) {
 		GroupParser parser;
 		try {
-			URL f = new URL(fileName);
-			ANTLRInputStream fs = new ANTLRInputStream(f.openStream(), encoding);
+			ANTLRInputStream fs = new ANTLRInputStream(url.openStream(), encoding);
 			GroupLexer lexer = new GroupLexer(fs);
-			fs.name = fileName;
+			fs.name = url.toString();
 			CommonTokenStream tokens = new CommonTokenStream(lexer);
 			parser = new GroupParser(tokens);
 			parser.group(this, prefix);
 		}
 		catch (Exception e) {
+			errMgr.IOError(null, ErrorType.CANT_LOAD_GROUP_FILE, e, url.toString());
+		}
+	}
+
+	/** Load a group file with full path {@code fileName}; it's relative to root by {@code prefix}. */
+	public void loadGroupFile(String prefix, String fileName) {
+		if ( verbose ) System.out.println(this.getClass().getSimpleName()+
+										  ".loadGroupFile(group-file-prefix="+prefix+", fileName="+fileName+")");
+		try {
+			URL url = new URL(fileName);
+			loadGroupURL(prefix, url);
+		} catch (Exception e) {
 			errMgr.IOError(null, ErrorType.CANT_LOAD_GROUP_FILE, e, fileName);
 		}
+
 	}
 
 	/** Load template file into this group using absolute {@code fileName}. */

src/org/stringtemplate/v4/STGroupFile.java

@@ -57,6 +57,8 @@ public class STGroupFile extends STGroup {
     /** Load a file relative to current directory or from root or via CLASSPATH. */
 	public STGroupFile(String fileName) { this(fileName, '<', '>'); }
 
+	public STGroupFile(URL url) { this(url, "UTF-8",'<', '>'); }
+
 	public STGroupFile(String fileName, char delimiterStartChar, char delimiterStopChar) {
 		super(delimiterStartChar, delimiterStopChar);
 		if ( !fileName.endsWith(GROUP_FILE_EXTENSION) ) {
@@ -138,7 +140,7 @@ public void load() {
 		// no prefix since this group file is the entire group, nothing lives
 		// beneath it.
 		if ( verbose ) System.out.println("loading group file "+url.toString());
-        loadGroupFile("/", url.toString());
+        loadGroupURL("/", url);
 		if ( verbose ) System.out.println("found "+templates.size()+" templates in "+url.toString()+" = "+templates.keySet());
     }