How to implement authentication with Apache Directory Server and Client Java API

This may not be a duplicate, but the second answer (by Nikolay Antipov) on the following question might answer your question: How to check user password in ldap whith java with given LdapContext?

This is a solution that can be used to authenticate a user with something else than the DN, for example with a uid or sAMAccountName.

The steps to do are:

1. Connect to the LDAP server
2. Authenticate with a service user of whom we know the DN and credentials
3. Search for the user you want to authenticate, search him with some attribute (for example sAMAccountName)
4. Get the DN of the user we found
5. Open another connection to the LDAP server with the found DN and the password
6. If the user is found and authentication works, you are fine

Code example:

public static boolean performAuthentication() {

    // service user
    String serviceUserDN = "cn=Mister Service,ou=Users,dc=example,dc=com";
    String serviceUserPassword = "abc123#!$";

    // user to authenticate
    String identifyingAttribute = "uid";
    String identifier = "maxdev";
    String password = "jkl987.,-";
    String base = "ou=Users,dc=example,dc=com";

    // LDAP connection info
    String ldap = "localhost";
    int port = 10389;
    String ldapUrl = "ldap://" + ldap + ":" + port;

    // first create the service context
    DirContext serviceCtx = null;
    try {
        // use the service user to authenticate
        Properties serviceEnv = new Properties();
        serviceEnv.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
        serviceEnv.put(Context.PROVIDER_URL, ldapUrl);
        serviceEnv.put(Context.SECURITY_AUTHENTICATION, "simple");
        serviceEnv.put(Context.SECURITY_PRINCIPAL, serviceUserDN);
        serviceEnv.put(Context.SECURITY_CREDENTIALS, serviceUserPassword);
        serviceCtx = new InitialDirContext(serviceEnv);

        // we don't need all attributes, just let it get the identifying one
        String[] attributeFilter = { identifyingAttribute };
        SearchControls sc = new SearchControls();
        sc.setReturningAttributes(attributeFilter);
        sc.setSearchScope(SearchControls.SUBTREE_SCOPE);

        // use a search filter to find only the user we want to authenticate
        String searchFilter = "(" + identifyingAttribute + "=" + identifier + ")";
        NamingEnumeration<SearchResult> results = serviceCtx.search(base, searchFilter, sc);

        if (results.hasMore()) {
            // get the users DN (distinguishedName) from the result
            SearchResult result = results.next();
            String distinguishedName = result.getNameInNamespace();

            // attempt another authentication, now with the user
            Properties authEnv = new Properties();
            authEnv.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
            authEnv.put(Context.PROVIDER_URL, ldapUrl);
            authEnv.put(Context.SECURITY_PRINCIPAL, distinguishedName);
            authEnv.put(Context.SECURITY_CREDENTIALS, password);
            new InitialDirContext(authEnv);

            System.out.println("Authentication successful");
            return true;
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (serviceCtx != null) {
            try {
                serviceCtx.close();
            } catch (NamingException e) {
                e.printStackTrace();
            }
        }
    }
    System.err.println("Authentication failed");
    return false;
}