Properly expand URI vars with regex

Before this commit UriComponents was capable of expanding URI vars that
may have contained a regular expressions (as supported with
@RequestMapping for example). However if the regular expressions
contained any nested "{}" the expand did not work correctly.

This commit sanitizes a URI template source removing any content
between nested "{}" prior to expanding. This works since we only care
about the URI variable name.

Issue: SPR-13311

spring-web/src/main/java/org/springframework/web/util/UriComponents.java

@@ -219,6 +219,9 @@ public abstract class UriComponents implements Serializable {
 		if (source.indexOf('{') == -1) {
 			return source;
 		}
+		if (source.indexOf(':') != -1) {
+			source = sanitizeSource(source);
+		}
 		Matcher matcher = NAMES_PATTERN.matcher(source);
 		StringBuffer sb = new StringBuffer();
 		while (matcher.find()) {
@@ -236,6 +239,27 @@ public abstract class UriComponents implements Serializable {
 		return sb.toString();
 	}
 
+	/**
+	 * Remove nested "{}" such as in URI vars with regular expressions.
+	 */
+	private static String sanitizeSource(String source) {
+		int level = 0;
+		StringBuilder sb = new StringBuilder();
+		for (char c : source.toCharArray()) {
+			if (c == '{') {
+				level++;
+			}
+			if (c == '}') {
+				level--;
+			}
+			if (level > 1 || (level == 1 && c == '}')) {
+				continue;
+			}
+			sb.append(c);
+		}
+		return sb.toString();
+	}
+
 	private static String getVariableName(String match) {
 		int colonIdx = match.indexOf(':');
 		return (colonIdx != -1 ? match.substring(0, colonIdx) : match);

spring-web/src/test/java/org/springframework/web/util/UriComponentsTests.java

@@ -16,10 +16,6 @@
 
 package org.springframework.web.util;
 
-import static org.hamcrest.Matchers.*;
-import static org.junit.Assert.*;
-import static org.springframework.web.util.UriComponentsBuilder.*;
-
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.ObjectInputStream;
@@ -27,9 +23,17 @@ import java.io.ObjectOutputStream;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.Arrays;
+import java.util.Collections;
 
 import org.junit.Test;
 
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.hamcrest.Matchers.not;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+import static org.springframework.web.util.UriComponentsBuilder.fromUriString;
+
 /**
  * @author Arjen Poutsma
  * @author Phillip Webb
@@ -82,6 +86,16 @@ public class UriComponentsTests {
 		assertEquals("http://example.com/1 2 3 4", uriComponents.toUriString());
 	}
 
+	// SPR-13311
+
+	@Test
+	public void expandWithRegexVar() {
+		String template = "/myurl/{name:[a-z]{1,5}}/show";
+		UriComponents uriComponents = UriComponentsBuilder.fromUriString(template).build();
+		uriComponents = uriComponents.expand(Collections.singletonMap("name", "test"));
+		assertEquals("/myurl/test/show", uriComponents.getPath());
+	}
+
 	// SPR-12123
 
 	@Test