domainExpiration/src/main/java/com/example/demo/demos/web/util/CertUtil.java

package com.example.demo.demos.web.util;


import javax.net.ssl.HttpsURLConnection;
import java.net.URL;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;

public class CertUtil {
    public static X509Certificate getCertificate(String url){
        URL u = null;
        HttpsURLConnection conn = null;
        try {
            u = new URL("https://"+url);
            conn = (HttpsURLConnection) u.openConnection();
            conn.connect();

            // 获取服务器证书链
            Certificate[] certificates = conn.getServerCertificates();
            // 通常证书链的第一个证书是服务器证书
            X509Certificate serverCert = (X509Certificate) certificates[0];

            return serverCert;
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if (conn != null) {
                conn.disconnect();
            }
        }
        return null;
    }
}