This articles serves as a troubleshooting guide.
When Liferay is configured to export users from the portal to LDAP, the following error is encountered:
09:18:31,903 ERROR [LoginAction:128] com.liferay.portal.ModelListenerException: javax.naming.directory.InvalidAttributeValueException: [LDAP: error code 21 - ERR_04083 The type cant be null]; remaining name 'cn=test2,ou=users,dc=example,dc=com'
com.liferay.portal.ModelListenerException: javax.naming.directory.InvalidAttributeValueException: [LDAP: error code 21 - ERR_04083 The type cant be null]; remaining name 'cn=test2,ou=users,dc=example,dc=com'
This error is caused because a necessary mapping for the export is missing and not being passed to the LDAP client. This results in a "null" error