Generating one excel file out of three other input excel files. Best approach?

[jonmikelm <jm...@ibermatica.com>]

Hi all,

I am adapting an old application originally developed with JExcelAPI to make
it compatible with xlsx file format using POI(3.8). One of the
functionalities consists in generating a new excel file out of three other
input excel files:

1. Input data file: 300-400 columns and 4000-8000 rows
2. Parametrization file: 4 sheets containing data which is used to process
the input data file and write it into the output file. (Sheet1: 1000-1500
rows, 25 columns - Sheets 2,3 & 4: 150-200 rows, 5 columns)
3. Template file: 2 sheets. The first 100 rows of each sheet(they are hidden
for the end user) contain data (lists) that are referred by de rows below.
4. The resulted file, contains 2 sheets, 35 columns and 1000 - 1500 rows
each.

I have replaced/adapted line by line every reference to the old JExcelAPI
library using POI (3.8), without changing the logic of the program. The
algorithm is as follows:

1. Parametrization file is read(ss usermodel) and cached in memory using 4
hashmaps (1 per sheet).
2. Output Workbook object is created from the template file.
3. Input data file is read(ss usermodel), matching cells with the
parametrization hashmap values in memory and writting the processed values
into the output Workbook object.
4. The output Workbook object is written to a File. 

The process is quite slower using POI than using the old API. 

Which would be the optimun/faster aproach to manage this?

thanks & regards

Jon Mikel






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