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Microsoft JDBC Driver for SQL Server. The Azure Key Vault feature in Microsoft JDBC Driver for SQL Server depends on Azure SDK for JAVA and Azure Active Directory Library For Java.

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/*
 * Microsoft JDBC Driver for SQL Server
 * 
 * Copyright(c) Microsoft Corporation All rights reserved.
 * 
 * This program is made available under the terms of the MIT License. See the LICENSE file in the project root for more information.
 */
package com.microsoft.sqlserver.jdbc.dns;

import java.util.Set;

import javax.naming.NameNotFoundException;
import javax.naming.NamingException;

public final class DNSKerberosLocator {

    private DNSKerberosLocator() {
    }

    /**
     * Tells whether a realm is valid.
     *
     * @param realmName
     *            the realm to test
     * @return true if realm is valid, false otherwise
     * @throws NamingException
     *             if DNS failed, so realm existence cannot be determined
     */
    public static boolean isRealmValid(String realmName) throws NamingException {
        if (realmName == null || realmName.length() < 2) {
            return false;
        }
        if (realmName.startsWith(".")) {
            realmName = realmName.substring(1);
        }
        try {
            Set records = DNSUtilities.findSrvRecords("_kerberos._udp." + realmName);
            return !records.isEmpty();
        }
        catch (NameNotFoundException wrongDomainException) {
            return false;
        }
    }
}