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Rename webapp/WEB-INF/web-servlet.xml to webapp/WEB-INF/web.xml, nothing should be changed in this file. This file is used by the servlet container (Tomcat) to configure the context of the application.
Create the directories used to store the uploaded files (see property uploadedFiles.path, e.g. /usr/local/helpdesk/files or c:/helpdesk/files) and the index (see property index.path, e.g. /usr/local/helpdesk/index or c:/helpdesk/index).
Start
Simply executing ant start should start the application.
Test
Browse http://localhost:8080http://localhost:8080 and start using the application.
Each time you change a property of the configuration files, you have to restart the application (ant restart).