Resolution:
The sample program:LDAPSearchLoginModule.java is provided through TIBCOmmunity at http://www.tibcommunity.com/docs/DOC-1250.

To setup LDAP authorization using this sample program, you need to do followings:

1. Build the sample java program into a jar file, for example: jaas_ldap.jar

2. Create the JAAS configuration file: jaas_ldap.conf, for example:

============================================
EMSUserAuthentication {
com.tibco.example.LDAPSearchLoginModule required
       ems_ldap.url="ldap://some_ldap_server:389"
       ems_ldap.binding_name="cn=Administrator,cn=users,dc=test,dc=some_company,dc=com"
       ems_ldap.binding_password="AdministratorPassword"
       ems_ldap.user_base_dn="cn=users,dc=test,dc=some_company,dc=com"
       ems_ldap.user_attribute="cn"
       ems_ldap.scope="subtree"
       ems_ldap.debug="enabled"
       ems_ldap.retries="10"
       ems_ldap.retry_delay="1000";
};
============================================

3. Modify the tibemsd-jaas.conf under {EMS_install_dir}/samples/security directory:

1). set jaas_config_file to jaas_ldap.conf.
2). set jaas_classpath to include jaas_ldap.jar
3). comment out the JACI prameters if you don't use JACI.
4). make sure jar_library is set to the correct JVM shared library installed on the machine.

Start EMS 5.x server with the configure file:tibemsd-jaas.conf and test external LDAP authorization.

How to setup external LDAP authorization using JAAS plugin feature in EMS 5.x?