Java LDAP - 确定给定组中的用户是否？

import javax.naming.directory.*;
import javax.naming.*;

public class LDAPSearch {
    public static void main(String[] args) {
        String ldapUrl = "ldap://localhost:389";
        String bindDn = "cn=admin,dc=example,dc=com";
        String bindPassword = "password";
        String searchBase = "ou=users,dc=example,dc=com";
        String searchFilter = "(memberOf=cn=groupName,ou=groups,dc=example,dc=com)";

        try {
            // Set up environment for authentication
            Hashtable<String, String> env = new Hashtable<String, String>();
            env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
            env.put(Context.PROVIDER_URL, ldapUrl);
            env.put(Context.SECURITY_AUTHENTICATION, "simple");
            env.put(Context.SECURITY_PRINCIPAL, bindDn);
            env.put(Context.SECURITY_CREDENTIALS, bindPassword);

            // Create initial context
            DirContext ctx = new InitialDirContext(env);

            // Create search controls
            SearchControls ctls = new SearchControls();
            ctls.setReturningAttributes(new String[]{"cn"});

            // Search for objects
            NamingEnumeration<SearchResult> answer = ctx.search(searchBase, searchFilter, ctls);

            // Print the answer
            while (answer.hasMore()) {
                SearchResult sr = answer.next();
                System.out.println("User: " + sr.getAttributes().get("cn").get());
            }

            // Close the context when we're done
            ctx.close();
        } catch (NamingException e) {
            e.printStackTrace();
        }
    }
}