Merge pull request #11202 from ptahchiev:11201

* pr/11202:
  Polish "Fix NullPointer when requesting a session that does not exist"
  Fix NullPointer when requesting a session that does not exist

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/session/SessionsEndpoint.java

@@ -60,6 +60,9 @@ public class SessionsEndpoint {
 	@ReadOperation
 	public SessionDescriptor getSession(@Selector String sessionId) {
 		Session session = this.sessionRepository.findById(sessionId);
+		if (session == null) {
+			return null;
+		}
 		return new SessionDescriptor(session);
 	}
 

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/session/SessionsEndpointTests.java

@@ -81,6 +81,12 @@ public class SessionsEndpointTests {
 		assertThat(result.isExpired()).isEqualTo(session.isExpired());
 	}
 
+	@Test
+	public void getSessionWithIdNotFound() {
+		given(this.repository.findById("not-found")).willReturn(null);
+		assertThat(this.endpoint.getSession("not-found")).isNull();
+	}
+
 	@Test
 	public void deleteSession() {
 		this.endpoint.deleteSession(session.getId());

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/session/SessionsEndpointWebIntegrationTests.java

@@ -80,6 +80,14 @@ public class SessionsEndpointWebIntegrationTests {
 				.isEqualTo(new JSONArray().appendElement(session.getId()));
 	}
 
+	@Test
+	public void sessionForIdNotFound() {
+		client.get()
+				.uri((builder) -> builder.path(
+						"/actuator/sessions/session-id-not-found").build())
+				.exchange().expectStatus().isNotFound();
+	}
+
 	@Configuration
 	protected static class TestConfiguration {