Support additional nullness signal for Actuator endpoints

This commit expands the detection of optional parameters for Actuator
Endpoints. Before this commit, JSpecify's `@Nullable` annotation was
not detected.

See gh-46854

Signed-off-by: wonyongg <111210881+wonyongg@users.noreply.github.com>

Author: wonyongg

configuration-metadata/spring-boot-configuration-processor/build.gradle

@@ -36,6 +36,7 @@ architectureCheck {
 
 dependencies {
 	testCompileOnly("com.google.code.findbugs:jsr305:3.0.2")
+	testCompileOnly("org.jspecify:jspecify")
 
 	testImplementation(enforcedPlatform(project(":platform:spring-boot-dependencies")))
 	testImplementation(project(":test-support:spring-boot-test-support"))

configuration-metadata/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/MetadataGenerationEnvironment.java

@@ -52,10 +52,13 @@
  * @author Stephane Nicoll
  * @author Scott Frederick
  * @author Moritz Halbritter
+ * @author Wonyong Hwang
  */
 class MetadataGenerationEnvironment {
 
-	private static final String NULLABLE_ANNOTATION = "org.springframework.lang.Nullable";
+	private static final Set<String> NULLABLE_ANNOTATIONS = Set.of(
+			"org.springframework.lang.Nullable",
+			"org.jspecify.annotations.Nullable");
 
 	private static final Set<String> TYPE_EXCLUDES = Set.of("com.zaxxer.hikari.IConnectionCustomizer",
 			"groovy.lang.MetaClass", "groovy.text.markup.MarkupTemplateEngine", "java.io.Writer", "java.io.PrintWriter",
@@ -265,6 +268,12 @@ AnnotationMirror getAnnotation(Element element, String type) {
 					return annotation;
 				}
 			}
+
+			for (AnnotationMirror annotation : element.asType().getAnnotationMirrors()) {
+				if (type.equals(annotation.getAnnotationType().toString())) {
+					return annotation;
+				}
+			}
 		}
 		return null;
 	}
@@ -368,7 +377,12 @@ AnnotationMirror getNameAnnotation(Element element) {
 	}
 
 	boolean hasNullableAnnotation(Element element) {
-		return getAnnotation(element, NULLABLE_ANNOTATION) != null;
+		for (String nullableAnnotation : NULLABLE_ANNOTATIONS) {
+			if (getAnnotation(element, nullableAnnotation) != null) {
+				return true;
+			}
+		}
+		return false;
 	}
 
 	boolean hasOptionalParameterAnnotation(Element element) {

configuration-metadata/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationprocessor/EndpointMetadataGenerationTests.java

@@ -35,6 +35,8 @@
 import org.springframework.boot.configurationsample.endpoint.SpecificEndpoint;
 import org.springframework.boot.configurationsample.endpoint.UnrestrictedAccessEndpoint;
 import org.springframework.boot.configurationsample.endpoint.incremental.IncrementalEndpoint;
+import org.springframework.boot.configurationsample.endpoint.NullableParameterEndpoint;
+import org.springframework.boot.configurationsample.endpoint.OptionalParameterEndpoint;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatRuntimeException;
@@ -45,6 +47,7 @@
  * @author Stephane Nicoll
  * @author Scott Frederick
  * @author Moritz Halbritter
+ * @author Wonyong Hwang
  */
 class EndpointMetadataGenerationTests extends AbstractMetadataGenerationTests {
 
@@ -192,6 +195,38 @@ void shouldFailIfEndpointWithSameIdButWithConflictingEnabledByDefaultSetting() {
 					"Existing property 'management.endpoint.simple.access' from type org.springframework.boot.configurationsample.endpoint.SimpleEndpoint has a conflicting value. Existing value: unrestricted, new value from type org.springframework.boot.configurationsample.endpoint.SimpleEndpoint3: none");
 	}
 
+	@Test
+	void nullableParameterEndpoint() {
+		ConfigurationMetadata metadata = compile(NullableParameterEndpoint.class);
+		assertThat(metadata).has(Metadata.withGroup("management.endpoint.nullable").fromSource(NullableParameterEndpoint.class));
+		assertThat(metadata).has(access("nullable", Access.UNRESTRICTED));
+		assertThat(metadata).has(cacheTtl("nullable"));
+		assertThat(metadata.getItems()).hasSize(3);
+	}
+
+	@Test
+	void optionalParameterEndpoint() {
+		ConfigurationMetadata metadata = compile(OptionalParameterEndpoint.class);
+		assertThat(metadata).has(Metadata.withGroup("management.endpoint.optional").fromSource(OptionalParameterEndpoint.class));
+		assertThat(metadata).has(access("optional", Access.UNRESTRICTED));
+		assertThat(metadata).has(cacheTtl("optional"));
+		assertThat(metadata.getItems()).hasSize(3);
+	}
+
+	@Test
+	void nullableAndOptionalParameterEquivalence() {
+		ConfigurationMetadata nullableMetadata = compile(NullableParameterEndpoint.class);
+		ConfigurationMetadata optionalMetadata = compile(OptionalParameterEndpoint.class);
+
+		assertThat(nullableMetadata.getItems()).hasSize(3);
+		assertThat(optionalMetadata.getItems()).hasSize(3);
+
+		assertThat(nullableMetadata).has(access("nullable", Access.UNRESTRICTED));
+		assertThat(optionalMetadata).has(access("optional", Access.UNRESTRICTED));
+		assertThat(nullableMetadata).has(cacheTtl("nullable"));
+		assertThat(optionalMetadata).has(cacheTtl("optional"));
+	}
+
 	private Metadata.MetadataItemCondition access(String endpointId, Access defaultValue) {
 		return defaultAccess(endpointId, endpointId, defaultValue);
 	}

configuration-metadata/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/endpoint/NullableParameterEndpoint.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.configurationsample.endpoint;
+
+import org.springframework.boot.configurationsample.Endpoint;
+import org.springframework.boot.configurationsample.ReadOperation;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * An endpoint with @Nullable parameter to test.
+ *
+ * @author Wonyong Hwang
+ */
+@Endpoint(id = "nullable")
+public class NullableParameterEndpoint {
+
+	@ReadOperation
+	public String invoke(@Nullable String parameter) {
+		return "test with " + parameter;
+	}
+
+}

configuration-metadata/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/endpoint/OptionalParameterEndpoint.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+ package org.springframework.boot.configurationsample.endpoint;
+
+ import org.springframework.boot.configurationsample.Endpoint;
+ import org.springframework.boot.configurationsample.ReadOperation;
+ import org.springframework.boot.configurationsample.OptionalParameter;
+ 
+ /**
+  * An endpoint with @OptionalParameter to compare with @Nullable behavior.
+  *
+  * @author Wonyong Hwang
+  */
+ @Endpoint(id = "optional")
+ public class OptionalParameterEndpoint {
+ 
+     @ReadOperation
+     public String invoke(@OptionalParameter String parameter) {
+         return "test with " + parameter;
+     }
+ 
+ }