Posts Tagged 'document'

Apache POI Speed Optimizations

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Category: Framework

Published on Monday, 29 October 2012 23:39

Written by Administrator

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The Apache POI Project's mission is to create and maintain Java APIs for manipulating various file formats based upon the Office Open XML standards (OOXML) and Microsoft's OLE 2 Compound Document format (OLE2). In short, you can read and write MS Excel files using Java. In addition, you can read and write MS Word and MS PowerPoint files using Java. Apache POI is your Java Excel solution (for Excel 97-2008). We have a complete API for porting other OOXML and OLE2 formats and welcome others to participate.

Switch Off logging

From the documentation at http://poi.apache.org/utils/logging.html

Logging in POI is used only as a debugging mechanism, not a normal runtime logging system. Logging is ONLY for autopsie type debugging, and should NEVER be enabled on a production system. Enabling logging will reduce performance by at least a factor of 100. If you are not developing POI or trying to debug why POI isn't reading a file correctly, then DO NOT enable logging. You've been warned.

In order to effectively disable the logging functionality in Apache POI you must use an alternative logger. This is accomplished by providing a property to the POILogFactory to override the default logger. You can add one of these –D to your JVM settings

-Dorg.apache.poi.util.POILogger=org.apache.poi.util.NullLogger

-Dorg.apache.poi.util.POILogger=org.apache.commons.logging.impl.NoOpLog

I found Apache POI to slightly better perform with the NoOpLog of apache common!

Recompile poi with more adapted settings

You can create a custom build of Apache POI 3.8 and alter the following properties to better match the size of the excel files you are generating or reading:

org.apache.poi.hssf.usermodel.HSSFRow#INITIAL_CAPACITY=5;

org.apache.poi.hssf.usermodel.HSSFSheet#INITIAL_CAPACITY= 20;    // used for compile-time optimization.  This is the initial size for the collection of rows.  It is currently set to 20.  If you generate larger sheets you may benefit by setting this to a higher number and recompiling a custom edition of HSSFSheet.

org.apache.poi.hssf.usermodel.HSSFWorkbook#INITIAL_CAPACITY=3;  // used for compile-time performance/memory optimization.  This determines the  initial capacity for the sheet collection.  Its currently set to 3.Changing it in this release will decrease performance since you're never allowed to have more or less than three sheets!     

http://poi.apache.org/apidocs/org/apache/poi/hssf/usermodel/HSSFWorkbook.html#INITIAL_CAPACITY

Don’t use xlsx, prefer xls!

This will only work if you do not reach xls limitations which may avoid you to go to that extreme solution. XLS is not compressed (XLSX is xml based and compressed) and your workbook may double size in memory as a result!

For example, data beyond 256 (IV) columns by 65,536 rows will not be saved in xls! In Excel 2010 and Excel 2007, the worksheet size is 16,384 columns by 1,048,576 rows, but the worksheet size of Excel 97-2003 is only 256 columns by 65,536 rows. Data in cells outside of this column and row limit is lost in Excel 97-2003. But there is a lot more limitations listed at office.com…

The biggest side effect was that my excel file went from 354kb to 967kb, but the speed increase was quite interesting: more than 44% less evaluation time.

Small localized optimization

I don’t think these bring a lot of speed, JIT should optimize this bad piece of code for us but it is always worth trying Speeding up org.apache.poi.hssf.usermodel.HSSFRow.compareTo() and http://affy.blogspot.ch/2004/04/poi-optimization-speeding-_108265938673224937.html

Linux Incompatibility List

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Category: Newsflash

Published on Sunday, 19 September 2004 00:00

Written by Administrator

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The Linux Incompatibility List is an attempt to catalog and document hardware/peripherals of all kinds that do not work with the Linux operating system. Fortunately, at this point in time, there is far, far more hardware that works without any problems with Linux, so this site aims to make Linux users aware of hardware to avoid

Metro: another tentative of user lock-in?

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Category: Krosoft case

Published on Tuesday, 14 June 2005 00:00

Written by Administrator

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Another lock-in of users  format full of promise by Microsoft: Metro
Metro will be based on XML (eXtensible Markup Language), an open standard widely used on the internet.
read more here:
Metro is basically M$ response to the widely use Adobe PDF (Portable Document File) file format...There is some articles which try to explain why M$ is now trying to control PDF:  Microsoft gunning for Adobe's PDF format? and  Microsoft Metro Threatens Adobe Acrobat, a very good article on what Metro may change in our lives.

Metro Specification and Reference Guide is available on M$ HERE

Note: If You ever want to create, read, modifiy PDF using Java, there is a huge list of open source libraries and tools list HERE

Free 96-page report details benefits of Open Source software

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Category: Supporting

Published on Wednesday, 22 September 2004 00:00

Written by Administrator

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Computer Sciences Corp. (CSC) has published a 96-page report on Open Source software and its potential benefits to business and government. This whitepaper provides an introduction to the report and its findings.