Allow separator configuration in PathPatternParser

This commit allows to configure a custom path separator when parsing and
matching path patterns with `PathPatternParser`, but also when parsing
incoming paths as `PathContainer` instances.

Closes gh-23092

spring-web/src/test/java/org/springframework/http/server/DefaultPathContainerTests.java

@@ -27,6 +27,7 @@ import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 
 /**
  * Unit tests for {@link DefaultPathContainer}.
@@ -111,15 +112,18 @@ public class DefaultPathContainerTests {
 		testPath("//%20/%20", "//%20/%20", Arrays.asList("/", "/", "%20", "/", "%20"));
 	}
 
-	private void testPath(String input, String value, List<String> expectedElements) {
-
-		PathContainer path = PathContainer.parsePath(input);
+	private void testPath(String input, String separator, String value, List<String> expectedElements) {
+		PathContainer path = PathContainer.parsePath(input, separator);
 
 		assertThat(path.value()).as("value: '" + input + "'").isEqualTo(value);
 		assertThat(path.elements().stream()
 				.map(PathContainer.Element::value).collect(Collectors.toList())).as("elements: " + input).isEqualTo(expectedElements);
 	}
 
+	private void testPath(String input, String value, List<String> expectedElements) {
+		testPath(input, "/", value, expectedElements);
+	}
+
 	@Test
 	public void subPath() throws Exception {
 		// basic
@@ -137,4 +141,14 @@ public class DefaultPathContainerTests {
 		assertThat(path.subPath(2).value()).isEqualTo("/b/");
 	}
 
+	@Test
+	public void pathWithCustomSeparator() throws Exception {
+		testPath("a.b.c", ".", "a.b.c", Arrays.asList("a", ".", "b", ".", "c"));
+	}
+
+	@Test
+	public void emptySeparator() {
+		assertThatIllegalArgumentException().isThrownBy(() -> PathContainer.parsePath("path", ""));
+	}
+
 }

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

@@ -408,6 +408,15 @@ public class PathPatternParserTests {
 		assertThat(patterns.get(1)).isEqualTo(p2);
 	}
 
+	@Test
+	public void separatorTests() {
+		PathPatternParser parser = new PathPatternParser();
+		parser.setSeparator('.');
+		String rawPattern = "first.second.{last}";
+		PathPattern pattern = parser.parse(rawPattern);
+		assertThat(pattern.computePatternString()).isEqualTo(rawPattern);
+	}
+
 	private PathPattern parse(String pattern) {
 		PathPatternParser patternParser = new PathPatternParser();
 		return patternParser.parse(pattern);