Perhaps with JNDI ?

I have used several more or less randomly chosen LDAP browsers to
communicate with an Exchange server without any problems. I don't
believe that OpenLDAP or JLDAP are incapable of this, so perhaps you
need to check your configuration or ensure that the LDAP server is
enabled in Exchange.

At any rate searching for Java LDAP gives many hits, including this
one (which I have just confirmed with our Exchange server):

http://www-unix.mcs.anl.gov/~gawor/ldap/

/gordon

Depending on where the data is stored that you want to access you may
not even need to access the Exchange server itself.

let me explain a bit:

Exchange uses ADS for it's infrastructure. Exchange really only controls
the storage of your mail, not the configuration of email addresses and
other things.

The following is based on personal experience with a project (not my
senior project that I talk about later) I worked on within the past year
for my job:
If you want to let a user access their outlook contacts then you will be
accessing something on the user's machine, not on the exchange server
(data from the exchange server is cached in outlook which alleviates the
need for you to go to the server in that case). This requires MAPI due
to a patch that Microsoft includes in Office 2000 SP3 (and included in
Office 2003) that shows a warning message to the user EVERYTIME a
non-approved application attempts to access the outlook address book
(due to all those worms a while back that did this unhindered).  All
MAPI apps are already approved to access the outlook address book and so
that warning will not appear.

If you need to do the above then you will need a Java API for MAPI and
as I mentioned in my earlier post, I only know of J-Integra that
provides that capability.

On the other hand, if you want to be able to access Exchange's Global
Address List (and get uncached and up-to-date data) and you want to
provide your own graphical interface (as in you don't want the Outlook
address book interface) then you can query the address book information
yourself. The actual entries are *not* on the exchange server but on the
active directory server. An Exchange address list is just a LDAP query
itself that Exchange stores so that you don't have to worry about always
adding a new user to the list; the query is auto-populated.

If you formulate your query correctly then you can get all the Contact
objects or just all objects that have an email address or whatever you
want.  This does not require MAPI and only requires, in your case, a
Java API that can talk LDAP. JNDI in Java can do this and in fact I have
written an application (and continue to work on it; it was my senior
project) that talks with various LDAP directory servers (ADS, OpenLDAP,
Sun) using the  LDAP protocol.

Based on that, you could do something very similar and provide your own
GUI. My program hasn't been publicly released and I don't expect to be
until the first of the year (fully functional but I'm adding a bunch of
features I want in before it goes public).

Decide what data you need first and how you want to present it. This
will dictate whether an API (such as JNDI) is already out there or if
you need to license one.

brandon