我找到了使用如何将.cer证书导入Java密钥库?(Patrick M的回答).

I found the solution using Using UnboundID SDK with an SSL certificate file to connect to LDAP server in Android app and How to import a .cer certificate into a java keystore? (answer of Patrick M).

现在，我可以从用户界面获取证书并通过SSL连接到LDAP了:)

Now I can take a certificate from UI and connect to LDAP via SSL :)

import com.unboundid.ldap.sdk.LDAPConnection;
import com.unboundid.util.ssl.SSLUtil;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import java.io.ByteArrayInputStream;
import java.security.KeyStore;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;

String base64EncodedCertificateString = "...";
ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(base64EncodedCertificateString.getBytes());
KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
trustStore.load(null);
CertificateFactory cf = CertificateFactory.getInstance("X.509");
int i = 0;
while (byteArrayInputStream.available() > 0) {
    Certificate cert = cf.generateCertificate(byteArrayInputStream);
    trustStore.setCertificateEntry("cert " + i++, cert);
}

TrustManagerFactory tmf = TrustManagerFactory.getInstance("X509");
tmf.init(trustStore);
TrustManager[] trustManagers = tmf.getTrustManagers();
SSLUtil sslUtil = new SSLUtil(trustManagers);
SSLSocketFactory socketFactory = sslUtil.createSSLSocketFactory();
LDAPConnection connection = new LDAPConnection(socketFactory);
connection.connect("place.myserver.com", 636);