Introduction

public class TraditionalPersonRepoImpl implements PersonRepo {
   public List<String> getAllPersonNames() {
      Hashtable env = new Hashtable();
      env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
      env.put(Context.PROVIDER_URL, "ldap://localhost:389/dc=example,dc=com");

      DirContext ctx;
      try {
         ctx = new InitialDirContext(env);
      } catch (NamingException e) {
         throw new RuntimeException(e);
      }

      List<String> list = new LinkedList<String>();
      NamingEnumeration results = null;
      try {
         SearchControls controls = new SearchControls();
         controls.setSearchScope(SearchControls.SUBTREE_SCOPE);
         results = ctx.*search*("", *"(objectclass=person)"*, controls);

         while (results.hasMore()) {
            SearchResult searchResult = (SearchResult) results.next();
            Attributes attributes = searchResult.getAttributes();
            *Attribute attr = attributes.get("cn");
            String cn = attr.get().toString();*
            list.add(cn);
         }
      } catch (NameNotFoundException e) {
         // The base context was not found.
         // Just clean up and exit.
      } catch (NamingException e) {
         throw new RuntimeException(e);
      } finally {
         if (results != null) {
            try {
               results.close();
            } catch (Exception e) {
               // Never mind this.
            }
         }
         if (ctx != null) {
            try {
               ctx.close();
            } catch (Exception e) {
               // Never mind this.
            }
         }
      }
      *return list;*
   }
}

import static org.springframework.ldap.query.LdapQueryBuilder.query;

public class PersonRepoImpl implements PersonRepo {
   private LdapClient ldapClient;

   public void setLdapClient(LdapClient ldapClient) {
      this.ldapClient = ldapClient;
   }

   public List<String> getAllPersonNames() {
      return ldapClient.search().query(
            *query().where("objectclass").is("person")*
         ).toObject((Attributes attrs) ->
            *attrs.get("cn").get().toString();*
         );
   }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:ldap="http://www.springframework.org/schema/ldap"
       xsi:schemaLocation="http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/ldap https://www.springframework.org/schema/ldap/spring-ldap.xsd">

   <ldap:context-source
          url="ldap://localhost:389"
          base="dc=example,dc=com"
          username="cn=Manager"
          password="secret" />

   <bean id="ldapClient" class="org.springframework.ldap.core.LdapClient" factory-method="create">
        <constructor-arg ref="contextSource" />
    </bean>

   <bean id="personRepo" class="com.example.repo.PersonRepoImpl">
      <property name="ldapClient" ref="ldapClient" />
   </bean>
</beans>