Improve expanding in MvcUriComponentsBuilder

Before this change MvcUriComponentsBuilder could not create a
UriComponentsBuilder for methods where the mapping has a URI variable
and no matching method argument for it.

For example a URI variable may be in the type-level mapping but not
all methods may have an @PathVariable argument for it.

This fix addresses the shortcoming such that MvcUriComponentsBuilder
expands the method argument values available to it and leaves remaining
URI variables to be further expanded via UriComponents.expand().

Issue: SPR-11391

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/MvcUriComponentsBuilderTests.java

@@ -34,6 +34,7 @@ import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.context.request.RequestContextHolder;
 import org.springframework.web.context.request.ServletRequestAttributes;
 import org.springframework.web.util.UriComponents;
+import org.springframework.web.util.UriComponentsBuilder;
 
 import java.util.Arrays;
 import java.util.List;
@@ -134,6 +135,15 @@ public class MvcUriComponentsBuilderTests {
 		assertThat(queryParams.get("offset"), contains("10"));
 	}
 
+	// SPR-11391
+
+	@Test
+	public void testFromMethodNameTypeLevelPathVariableWithoutArgumentValue() throws Exception {
+		UriComponents uriComponents = fromMethodName(UserContactController.class, "showCreate", 123).build();
+
+		assertThat(uriComponents.getPath(), is("/user/123/contacts/create"));
+	}
+
 	@Test
 	public void testFromMethodNameNotMapped() throws Exception {
 		UriComponents uriComponents = fromMethodName(UnmappedController.class, "unmappedMethod").build();
@@ -290,4 +300,13 @@ public class MvcUriComponentsBuilderTests {
 		}
 	}
 
+	@RequestMapping("/user/{userId}/contacts")
+	static class UserContactController {
+
+		@RequestMapping("/create")
+		public String showCreate(@PathVariable Integer userId) {
+			return null;
+		}
+	}
+
 }