Validate that sslInfo is not null in SslHealthIndicator constructor

The SslHealthIndicator constructor previously did not validate if the
provided SslInfo instance was null. This could potentially lead to a
NullPointerException later when the doHealthCheck method is invoked
if the SslInfo bean was not properly configured or available.

This commit adds an Assert.notNull check for the sslInfo parameter
to ensure fail-fast behavior during application startup or bean
creation. This aligns with the common practice in other Spring Boot
components and health indicators where essential dependencies are
validated in the constructor.

See gh-45013

Signed-off-by: geniuus <cross_man@naver.com>

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/ssl/SslHealthIndicator.java

@@ -28,12 +28,14 @@ import org.springframework.boot.info.SslInfo;
 import org.springframework.boot.info.SslInfo.BundleInfo;
 import org.springframework.boot.info.SslInfo.CertificateChainInfo;
 import org.springframework.boot.info.SslInfo.CertificateInfo;
+import org.springframework.util.Assert;
 
 /**
  * {@link HealthIndicator} that checks the certificates the application uses and reports
  * {@link Status#OUT_OF_SERVICE} when a certificate is invalid.
  *
  * @author Jonatan Ivanov
+ * @author Young Jae You
  * @since 3.4.0
  */
 public class SslHealthIndicator extends AbstractHealthIndicator {
@@ -41,6 +43,8 @@ public class SslHealthIndicator extends AbstractHealthIndicator {
 	private final SslInfo sslInfo;
 
 	public SslHealthIndicator(SslInfo sslInfo) {
+		super("SSL health check failed");
+		Assert.notNull(sslInfo, "'sslInfo' must not be null");
 		this.sslInfo = sslInfo;
 	}