Align server contextual names with OTel conventions

This commit ensures that the matching path pattern for the request being
observed is used in the conytextual name, as advised in the OTel HTTP
server semantic conventions.

If the path pattern is not available, no additional value is provided
and the "http {method}" baseline is being used.

Fixes gh-29424

Author: bclozel

spring-web/src/main/java/org/springframework/http/observation/DefaultServerRequestObservationConvention.java

@@ -76,6 +76,10 @@ public String getName() {
 
 	@Override
 	public String getContextualName(ServerRequestObservationContext context) {
+		if (context.getPathPattern() != null) {
+			return String.format("http %s %s", context.getCarrier().getMethod().toLowerCase(),
+					context.getPathPattern());
+		}
 		return "http " + context.getCarrier().getMethod().toLowerCase();
 	}
 

spring-web/src/main/java/org/springframework/http/observation/reactive/DefaultServerRequestObservationConvention.java

@@ -79,6 +79,10 @@ public String getName() {
 
 	@Override
 	public String getContextualName(ServerRequestObservationContext context) {
+		if (context.getPathPattern() != null) {
+			return String.format("http %s %s", context.getCarrier().getMethod().name().toLowerCase(),
+					context.getPathPattern().toString());
+		}
 		return "http " + context.getCarrier().getMethod().name().toLowerCase();
 	}
 

spring-web/src/test/java/org/springframework/http/observation/DefaultServerRequestObservationConventionTests.java

@@ -50,6 +50,12 @@ void shouldHaveContextualName() {
 		assertThat(convention.getContextualName(this.context)).isEqualTo("http get");
 	}
 
+	@Test
+	void contextualNameShouldUsePathPatternWhenAvailable() {
+		this.context.setPathPattern("/test/{name}");
+		assertThat(convention.getContextualName(this.context)).isEqualTo("http get /test/{name}");
+	}
+
 	@Test
 	void supportsOnlyHttpRequestsObservationContext() {
 		assertThat(this.convention.supportsContext(this.context)).isTrue();

spring-web/src/test/java/org/springframework/http/observation/reactive/DefaultServerRequestObservationConventionTests.java

@@ -49,6 +49,14 @@ void shouldHaveContextualName() {
 		assertThat(convention.getContextualName(context)).isEqualTo("http get");
 	}
 
+	@Test
+	void contextualNameShouldUsePathPatternWhenAvailable() {
+		ServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.get("/test/resource"));
+		ServerRequestObservationContext context = new ServerRequestObservationContext(exchange);
+		context.setPathPattern(PathPatternParser.defaultInstance.parse("/test/{name}"));
+		assertThat(convention.getContextualName(context)).isEqualTo("http get /test/{name}");
+	}
+
 	@Test
 	void supportsOnlyHttpRequestsObservationContext() {
 		ServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.post("/test/resource"));