Metacat

Modified the documentation.

Change it from an interface to an abstract class in the document.

add MapStore/Loader test for the IndexEvents -- adding and removing events in the DB table through hazelcast. https://projects.ecoinformatics.org/ecoinfo/issues/5944

move IndexEvent into metacat-common. Perparation for Metacat responding to events and writing them to a persistent store. https://projects.ecoinformatics.org/ecoinfo/issues/5944

Rename a method to isEnabled.

Remove the obsoleted class.

Add a class to repsent the enabled engine list.

use ContentTypeInputStream interface (and ByteArray implementation) to specify the desired content-type of the InputStream returned by MN.query().

Remove the code to throw an exception if the subjects is null in the query method.

changed the xpath to get solr_spec_version.