SSLContextを使ってSSLの有効期限を取得する

import java.io.InputStream;
import java.security.KeyStore;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;
import java.util.Date;

import javax.net.SocketFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.servlet.ServletContext;

public class CertCheck {
    static final long ONE_DAY = 1000L * 60 * 60 * 24;
    private Long limitDate = null;
    private Long period = null;

    public boolean doCheck(String host, ServletContext servletContext) {
        try {
            Date now = new Date();
            KeyStore keyStore = KeyStore.getInstance("JKS");
            InputStream stream = servletContext
                    .getResourceAsStream("/cert/cacerts");
            keyStore.load(stream, "changeit".toCharArray());
            TrustManagerFactory tmf = TrustManagerFactory.getInstance("PKIX");
            tmf.init(keyStore);

            SSLContext context = SSLContext.getInstance("TLS");
            TrustManager[] tms = { new DoNothingTrustManager() };
            context.init(null, tms, null);

            SocketFactory sf = context.getSocketFactory();
            SSLSocket soc = (SSLSocket) sf.createSocket(host, 443);

            soc.startHandshake();
            SSLSession session = soc.getSession();
            Certificate[] certArray = session.getPeerCertificates();

            try {
                if (certArray == null || certArray.length <= 0) {
                    throw new Exception("No certifications!");
                } else {
                    X509Certificate cert = (X509Certificate) certArray[0];
                    Date limit = cert.getNotAfter();
                    this.limitDate = limit.getTime();
                    this.period = ((limit.getTime() - now.getTime()) / ONE_DAY);
                    return true;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }
}