PathPattern#matchAndExtract minor refactoring

Consistent behavior with matches(PathContainer), the two had slightly
different logic for handling of empty paths.

Make matchAndExtract independantly usable without the need to call
matches(PathContainer) first. Essentially no longer raising ISE if the
pattern doesn't match but simply returning null.

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/util/pattern/PathPattern.java

@@ -175,26 +175,28 @@ else if (!hasLength(pathContainer)) {
 		MatchingContext matchingContext = new MatchingContext(pathContainer, false);
 		return this.head.matches(0, matchingContext);
 	}
-	
+
 	/**
 	 * Match this pattern to the given URI path and return extracted URI template
 	 * variables as well as path parameters (matrix variables).
 	 * @param pathContainer the candidate path to attempt to match against
-	 * @return info object with the extracted variables
-	 * @throws IllegalStateException if the path does not match the pattern
+	 * @return info object with the extracted variables, or {@code null} for no match
 	 */
+	@Nullable
 	public PathMatchInfo matchAndExtract(PathContainer pathContainer) {
-		MatchingContext matchingContext = new MatchingContext(pathContainer, true);
-		if (this.head != null && this.head.matches(0, matchingContext)) {
-			return matchingContext.getPathMatchResult();
+		if (this.head == null) {
+			return hasLength(pathContainer) ? null : PathMatchInfo.EMPTY;
 		}
 		else if (!hasLength(pathContainer)) {
-			return PathMatchInfo.EMPTY;
-		}
-		else {
-			throw new IllegalStateException(
-					"Pattern \"" + this + "\" is not a match for \"" + pathContainer.value() + "\"");
+			if (this.head instanceof WildcardTheRestPathElement || this.head instanceof CaptureTheRestPathElement) {
+				pathContainer = EMPTY_PATH; // Will allow CaptureTheRest to bind the variable to empty
+			}
+			else {
+				return null;
+			}
 		}
+		MatchingContext matchingContext = new MatchingContext(pathContainer, true);
+		return this.head.matches(0, matchingContext) ? matchingContext.getPathMatchResult() : null;
 	}
 
 	/**

spring-web/src/test/java/org/springframework/web/util/pattern/PathPatternTests.java

@@ -768,20 +768,10 @@ public void extractUriTemplateVariables() throws Exception {
 		checkCapture("/{page}.*", "/42.html", "page", "42");
 		checkCapture("/A-{B}-C", "/A-b-C", "B", "b");
 		checkCapture("/{name}.{extension}", "/test.html", "name", "test", "extension", "html");
-		try {
-			checkCapture("/{one}/", "//", "one", "");
-			fail("Expected exception");
-		}
-		catch (IllegalStateException e) {
-			assertEquals("Pattern \"/{one}/\" is not a match for \"//\"", e.getMessage());
-		}
-		try {
-			checkCapture("", "/abc");
-			fail("Expected exception");
-		}
-		catch (IllegalStateException e) {
-			assertEquals("Pattern \"\" is not a match for \"/abc\"", e.getMessage());
-		}
+
+		assertNull(checkCapture("/{one}/", "//"));
+		assertNull(checkCapture("", "/abc"));
+
 		assertEquals(0, checkCapture("", "").getUriVariables().size());
 		checkCapture("{id}", "99", "id", "99");
 		checkCapture("/customer/{customerId}", "/customer/78", "customerId", "78");

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/RequestPredicates.java

@@ -343,10 +343,10 @@ public PathPatternPredicate(PathPattern pattern) {
 		@Override
 		public boolean test(ServerRequest request) {
 			PathContainer pathContainer = request.pathContainer();
-			boolean match = this.pattern.matches(pathContainer);
-			traceMatch("Pattern", this.pattern.getPatternString(), request.path(), match);
-			if (match) {
-				mergeTemplateVariables(request, this.pattern.matchAndExtract(pathContainer).getUriVariables());
+			PathPattern.PathMatchInfo info = this.pattern.matchAndExtract(pathContainer);
+			traceMatch("Pattern", this.pattern.getPatternString(), request.path(), info != null);
+			if (info != null) {
+				mergeTemplateVariables(request, info.getUriVariables());
 				return true;
 			}
 			else {