View System Requests

IBIS-PH View System Requests

• User makes a request (via a browser) to an application server/application
• Application server determines the application (via context mapping)
• Request goes through a filter chain (according to the filter request mapping)
• Request then is handed to the servlet (according to the servlet request mapping)
• Servlet looks up the appropriate controller object
• Servlet calls the controller object's "handleRequest" method
• Controller determines the appropriate XML data model and XSLT view object then creates and returns a ModelAndView object
• Servlet then calls the returned ModelAndView object to get the view
• Servlet then calls the View object's "render" method with the model passed as an argument
• View's render method does the XSLT/XML transformation and returns the response
• Filter/response wrapping is then given control as the response bubbles back up through the filter chain (FILO)
• Response is streamed back to the user/browser that made the request

URL Request Anatomy

protocol://address:port/application_context/resource
  ?parameter_1_name=parameter_1_value
  &parameter_2_name=parameter_2_value
  . . . 
  &parameter_N_name=parameter_N_value
		

http://ibis.health.utah.gov:8080/ibisph-view/query/result
  ?GraphicType=jpeg&GraphicName=StackedArea
		

http://ibis.health.utah.gov/home/welcome.html
		

General IBIS Request Flow Overview

1. User makes a request
2. Request hits Java app server via "http://server_address_or_dns_name:IP_port". The Java app server determines the application by using an application context map. In the Tomcat Java app server it has a configuration file (config/server.xml) that contains among other settings, an application context to the application's deployment directory.
3. The web application (based on the context) is then handed the request. The application control first checks for servlet filters and wraps the request and response as applicable. Servlet filters are controlled with URL mappings. These mappings and filter control properties are specified in the application's "web.xml" file (located within the application's "WEB-INF" directory. See the filters page for more information about the IBIS-PH View System's Filters. The order the filters are listed corrsponds 1:1 with the order which the filters are applied in the filter chain.
4. The application's Java servlets are then called. Again specified and controlled with URL mappings like the filters in the "web.xml" file. The IBIS-PH View System uses only one servlet - the Spring Framework's Web MVC RequestDispatcher servlet. This servlet is not part of the IBIS Java code. It exists as part of the Spring Web MVC Framework.
5. The servlet init parameter named "contextConfigLocation" controls the RequestDispatcher's main configuration properties. This property contains "/WEB-INF/config/beans/dispatcher_servlet.xml". This property file specifies a special Spring MVC Web bean object named "SimpleUrlHandlerMapping". This bean configuration also contains a list mapping of URL to controllers.
6. The Spring Web MVC Framework is centered around the Spring Controller, the Spring Model, and the Spring View interfaces/objects. The RequestDispatcher uses this SimpleUrlHandlerMapping object to look up which controller should handle which request based again on the URL. The controllers can either handle the response or return a Spring Model and View object which are then used by the servlet to return a response to the requestor. The IBIS controllers typically contain some logic/business rules to determine which XML document/data file to be used (model). The view object to use is typically the transformation engine with the XSLT being specified by as a property of the view.
7. The RequestDispatcher servlet uses the Model and View object returned by the controller call to create the response to the user's request.

Main IBIS Request Flows