path params - allow underscores in path param names

This fixes #170

restx-core/src/main/java/restx/StdRestxRequestMatcher.java

@@ -112,6 +112,11 @@ void parse() {
         void end(PathPatternParser pathPatternParser);
     }
 
+    private static boolean isValidPathParamNameChar(int curChar) {
+        //only letters/digit/underscore are authorized in path param name
+        return Character.isLetterOrDigit(curChar) || curChar == '_';
+    }
+
     private static final class CurlyBracesPathParamPathParserCharProcessor implements PathParserCharProcessor {
         private int openBr = 1;
         private boolean inRegexDef;
@@ -166,8 +171,8 @@ public void handle(int curChar, PathPatternParser pathPatternParser) {
                     inRegexDef = true;
                     pathParamRegex.append("(");
                 } else {
-                    if (!Character.isLetterOrDigit(curChar)) {
-                        //only letters are authorized in path param name
+                    if (!isValidPathParamNameChar(curChar)) {
+                        //only letters/digit/underscore are authorized in path param name
                         throw new IllegalArgumentException(String.format(
                                 "illegal path parameter definition '%s' at offset %d" +
                                         " - only letters and digits are authorized in path param name",
@@ -188,7 +193,7 @@ public void end(PathPatternParser pathPatternParser) {
         private StringBuilder pathParamName = new StringBuilder();
         @Override
         public void handle(int curChar, PathPatternParser pathPatternParser) {
-            if (!Character.isLetterOrDigit(curChar)) {
+            if (!isValidPathParamNameChar(curChar)) {
                 pathPatternParser.patternBuilder.append("([^\\/]+)");
                 pathPatternParser.stdPathPatternBuilder.append("{").append(pathParamName).append("}");
                 pathPatternParser.groupNamesBuilder.add(pathParamName.toString());

restx-samplest/src/main/java/samplest/core/ParametersResource.java

@@ -46,9 +46,9 @@ public void setVal(String val) {
         }
     }
 
-    @GET("/params/path/{a}/:b/{c:\\d+}:d")
-    public String pathparams(String a, String b, String c, String d) {
-        return "a=" + a + " b=" + b + " c=" + c + " d=" + d;
+    @GET("/params/path/{a}/:_b/{c:\\d+}:d")
+    public String pathparams(String a, String _b, String c, String d) {
+        return "a=" + a + " b=" + _b + " c=" + c + " d=" + d;
     }
 
     @GET("/params/query/withOptionalString")