Chapter 17 Using the Asynchronous Interface

This chapter shows you how to use the Asynchronous Interface to LDAP in Java applications.

• "Synchronous vs. Asynchronous Connections"
• "Common Uses for the Asynchronous Interface"
• "New Classes in the Asynchronous Interface"
• "Performing Asynchronous Searches"
• "Where to Go for More Information"

• LDAPMessage, which is the base class for LDAP request and response messages.
• LDAPResponse, which extends LDAPMessage, represents a message received from an LDAP server in response to a request.
• LDAPExtendedResponse, which extends LDAPResponse. It is the response that an LDAP server returns when handling an extended operation request.
• LDAPResponseListener queues LDAPResponse messages.
• LDAPSearchResult, which extends LDAPMessage. It contains a single LDAP entry and is one of the responses that an LDAP server can return when handling a search request.
• LDAPSearchResultReference, which extends LDAPMessage. It contains a referral and is one of the responses that an LDAP server can return when handling a search request.
• LDAPSearchListener queues search results and references.

1. Connect to all the servers.
2. Create a response listener for one search.
3. Share the response listener all the other searches.
4. Obtain and process the results.
5. Disconnect from the servers.

import netscape.ldap.*;

import java.util.*;

/* This example multiplexes the input from three different servers */

public class MultiplexServers {

   public static void main( String[] args )

   {

      try {

         LDAPAsynch[] ld = new LDAPAsynch[3];

         String[] hosts = { "foo1", "foo2", "foo3" };

         int[] ports = { 389, 389, 2018 }

         String[] bases =

            { "o=Airius.com", "o=Acme.com", "dc=Acme,dc=com" };

         /* search for all entries with surname of Jensen */

         String MY_FILTER = "sn=Jensen";

         for( int i = 0; i < ld.length; i++ ) {

            ld[i] = new LDAPAsynch();

            /* Connect to server */

            ld[i].connect( hosts[i], ports[i] );

         }

         /* Get a response listener for one search */

         LDAPSearchListener l =

            ld[0].search( bases[0],

                          ld.SCOPE_SUB,

                          MY_FILTER,

                          null,

                          false,

                          (LDAPSearchListener)null );

         /* Share the listener */

         for( i = 1; i < ld.length; i++ ) {

            ld[i].search( bases[i],

                          ld[i].SCOPE_SUB,

                          MY_FILTER,

                          null,

                          false,

                          l );

         }

         /* Loop on results until finished */

         LDAPMessage msg;

         while( (msg = l.getResponse()) != null ) {

            if ( msg instanceof LDAPSearchResultReference ) {

               String[] urls =

                  ((LDAPSearchResultReference)msg).getUrls();

               // Do something with the referrals...

            } else if ( msg instanceof LDAPSearchResult ) {

               LDAPEntry entry =

                  ((LDAPSearchResult)msg).getEntry();

               // The rest of the processing is the same as for

               // a synchronous search

               System.out.println( entry.getDN() );

            } else {

               // A search response

               LDAPResponse res = (LDAPResponse)msg;

               int status = res.getResultCode();

               if ( status == LDAPException.SUCCESS ) {

                  // Nothing to do

               } else {

                  String err =

                     LDAPException.errorCodeToString(status);

                  throw new LDAPException(

                                          err,

                                          status,

                                          res.getErrorMessage(),

                                          res.getMatchedDN() );

               }

            }

         }

      } catch ( LDAPException e ) {

         System.err.println( e.toString() );

      }

      /* Done, so disconnect */

      if ( ld.isConnected() ) {

         ld.disconnect();

      }

   }

}

1. Connect to the server.
2. Create a response listener for one search.
3. Share (multiplex) the response listener with the other searches.
4. Obtain and process the results.
5. Disconnect from the server.

import netscape.ldap.*;

import java.util.*;

/* This example multiplexes the input from three searches in

different subtrees of the same server */

public class MultiplexTrees {

   public static void main( String[] args )

   {

      try {

         LDAPAsynch ld = new LDAPAsynch();

         /* Connect to server */

         String MY_HOST = "localhost";

         int MY_PORT = 389;

         ld.connect( MY_HOST, MY_PORT );

         String MY_FILTER = "sn=Jensen";

         String[] bases =

            { "o=Airius.com", "o=Acme.com", "dc=Acme,dc=com" };

         /* Get a response listener for one search */

         LDAPSearchListener l =

            ld.search( bases[0],

                       ld.SCOPE_SUB,

                       MY_FILTER,

                       null,

                       false,

                       (LDAPSearchListener)null );

         /* Share the listener */

         for( i = 1; i < bases.length; i++ ) {

            ld.search( bases[i],

                       ld.SCOPE_SUB,

                       MY_FILTER,

                       null,

                       false,

                       l );

         }

         /* Loop on results until finished */

         LDAPMessage msg;

         while( (msg = l.getResponse()) != null ) {

            /* The rest is the same as in the previous example */

            /* ... */