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Chapter 12. Deploying Crystal Enterprise... > Interaction Between the Web Componen...

Interaction Between the Web Component Server and the Web Connector

To demonstrate the interaction between the Web connector and the Web Component Server, it’s easiest to review the process of displaying a Crystal Report on a Crystal Viewer to examine exactly what traffic is being passed between the browser, Web server, Web connector, and the Crystal Enterprise report processing tier. Chapter 3 introduced this concept.

  1. A request is made from the browser to the Web server for a specific report file. In this example, the user has clicked on a hyperlink (http://<Server Name>/directory/myreport.rpt), meaning that a request has been made to view a Crystal Report within the Crystal Viewer.

  2. The connector on the Web server forwards the request to the Web Component Server.

  3. The Web Component Server calls a plug-in; in this example it will call wcs_xn_reportviewer.dll. This plug-in tells the Web Component Server to send the appropriate HTML to the browser that will load a Crystal Report Viewer.

  4. After the viewer has been loaded in the browser the viewer will request the same report file. To speed up the report delivery process the browser will be told by the WCS to load only the first page of the report. If the end user requires more pages of the report they will be served up on demand.

  5. The viewer’s request is received by the Web server and forwarded to the connector.

  6. The connector forwards the request to the WCS. The plug-in parses the query string and tells the WCS to check with the APS.

  7. The WCS asks the APS whether a guest account is available to access the report. This emulates a Crystal Reports .rpt request. One of the differences between Crystal Reports and Crystal Enterprise is that the APS keeps track of every Crystal Enterprise user, so a guest account is necessary. The concept is similar to the way anonymous authentication is used by Internet Information Server.

  8. The APS returns the name of an available Cache Server. The WCS now checks with the connector to determine the location of the report file. (Remember that the connector can be configured to resolve the physical location of the report file through virtual directory mapping.)

  9. The connector will check its configuration to see whether it resolves this URL to a specific directory for .rpt files. If not, the connector will ask the Web Server for the physical directory that this URL references.

  10. The WCS goes to the specified Cache Server and asks for incomplete page 1 of the report (the viewer’s URL request). The Cache Server checks for a cached copy of the page. If the page is not available, it forwards the request to a Page Server. The Cache Server knows which Page Server to pass the request to because the Page Server has broadcast its presence on the CORBA Bus.

  11. The Page Server goes to the location (as specified either by the connector or the Web server) and retrieves a copy of the report. The Page Server processes the report.

  12. The incomplete page is placed in cache and returned to the browser. Subsequent pages of the report may be requested by the user—in this case, the pages will be retrieved directly from the Cache Server.



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