Monday, 19 March 2012

NextReports Engine : Report Conversion

Version 5.1 of NextReports was already released, but  there is the time to look into next version.

One of the biggest feature, NextReports will resolve in version 5.2 is report conversion. This is not a 'visible' feature to the end user, but a back-end functionality.

NextReports supported from start back-end compatibility with older type of reports. Any new functionality was brought to life without breaking compatibility. For NextReports Engine users (developers) this means that anytime when a ReportUtil.loadReport(String xml) or a ReportUtil.loadReport(InputStream is) was done, no xml exception was raised.

To be more flexible in NextReports evolution, an entirely new convert process was integrated. Using a chain of xml converters, a Next report can be modified to a new structure. Practically if a report with version X is loaded by an Y version of engine, where Y > X, the load method will do the following:
  • get report version (X in this case)
  • apply a converter chain process if needed
  • load the resulted xml
To explain the second step,  for example if we have a Converter_X1 (to version X1) and a Converter_X2 (to version X2) with X < X1 < X2 < Y then conversions X->X1 and X1->X2 are needed,they are applied using a chain of responsibility order and the new version of report is set to Y.

The only differences to NextReports Engine are the signatures of the load methods from ReportUtil class which now throw a LoadReportException:

public static Report loadReport(String xml) throws LoadReportException { ... }

public static Report loadReport(InputStream is) throws LoadReportException { ... }

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