Important: Previous commit will not work. I add the actual cecker in this one.

src/main/java/eu/dnetlib/validatorapi/utils/CheckCertificate.java

@@ -0,0 +1,36 @@
+package eu.dnetlib.validatorapi.utils;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import javax.net.ssl.HttpsURLConnection;
+import javax.net.ssl.SSLPeerUnverifiedException;
+import java.net.URL;
+import java.security.cert.Certificate;
+
+public class CheckCertificate {
+    private static final Logger log = LogManager.getLogger(CheckCertificate.class);
+
+    public static boolean isValidCertificate(String httpsURL) {
+        try {
+            URL myUrl = new URL(httpsURL);
+            HttpsURLConnection conn = (HttpsURLConnection) myUrl.openConnection();
+            conn.connect();
+
+            // Get the certificate
+            Certificate[] certs = conn.getServerCertificates();
+            conn.disconnect();
+
+            return true;
+
+        } catch (SSLPeerUnverifiedException ssle) {
+            log.error("Certificate Validation Error.", ssle);
+            return false;
+
+        } catch (Exception e) {
+            log.error("Certificate Validation Error.", e);
+            return false;
+        }
+    }
+}
+