Can Google App Engine read from app using JXL but not Apache POI?

[slugmandrew via StackOverflow]

I've been using JXL for a while to process excel files from inside the webapp folder. This works in both development and production. I just inject a ServletContext and call something like:

Workbook.getWorkbook(new File(servletContext.getRealPath("WEB-INF/myfile.xls"))) and JXL can read the file and process it.

Now I need to switch to using Apache POI, as JXL can only read .xls files, and not .xlsx ones (which can have more than 65536 rows).

When I try to do the same using POI I get an exception:

[ERROR] java.security.AccessControlException: access denied ("java.io.FilePermission" "C:\Users\Drew\IntelliJ\UsavApp\target\UsavAppV7-1.0-SNAPSHOT\WEB-INF\myfile.xlsx" "write")
[ERROR]     at java.security.AccessControlContext.checkPermission(AccessControlContext.java:372)
[ERROR]     at java.security.AccessController.checkPermission(AccessController.java:559)
[ERROR]     at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
[ERROR]     at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:429)
[ERROR]     at java.lang.SecurityManager.checkWrite(SecurityManager.java:979)
[ERROR]     at java.io.RandomAccessFile.<init>(RandomAccessFile.java:229)
[ERROR]     at org.apache.poi.poifs.nio.FileBackedDataSource.newSrcFile(FileBackedDataSource.java:130)
[ERROR]     at org.apache.poi.poifs.nio.FileBackedDataSource.<init>(FileBackedDataSource.java:46)
[ERROR]     at org.apache.poi.poifs.filesystem.NPOIFSFileSystem.<init>(NPOIFSFileSystem.java:218)
[ERROR]     at org.apache.poi.poifs.filesystem.NPOIFSFileSystem.<init>(NPOIFSFileSystem.java:166)
[ERROR]     at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:278)
[ERROR]     at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:250)
[ERROR]     at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:229)
[ERROR]     at com.utilitiessavings.usavappv7.server.handler.parse.ParseElecTariffBooksHandler.processTariffsFromExcel(ParseElecTariffBooksHandler.java:108)
[ERROR]     at com.utilitiessavings.usavappv7.server.handler.parse.ParseElecTariffBooksHandler.execute(ParseElecTariffBooksHandler.java:91)
[ERROR]     at com.utilitiessavings.usavappv7.server.handler.parse.ParseElecTariffBooksHandler.execute(ParseElecTariffBooksHandler.java:39)
...etc

From reading around I gather POI isn't totally compatible with GAE, but most people talk about creating files from scratch, or writing them to the local disk. I'm not doing either of those so I wanted to be sure this is a limitation of App Engine and not something I'm doing.

My guess from the exception would be that POI needs write access even to read the file, whereas JXL didn't. Anyone shed any light on this?

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http://stackoverflow.com/questions/34676553/can-google-app-engine-read-from-app-using-jxl-but-not-apache-poi

[Gagravarr via StackOverflow]

Promoting a comment to an answer - in a case like this you should explicitly tell Apache POI to open your file in read-only mode

For a .xlsx file, do that with

OPCPackage pkg = OPCPackage.open(new File("input.xlsx"), PackageAccess.READ);
XSSFWorkbook wb = new XSSFWorkbook(pkg);

For a .xls file, do that with

NPOIFSFileSystem fs = new NPOIFSFileSystem(new File("input.xls"), true);
HSSFWorkbook wb = new HSSFWorkbook(fs);

Reading from an InputStream is always read-only, it's with Files where there's an option

See the constructor javadocs for a little bit more details

Please DO NOT REPLY directly to this email but go to StackOverflow:

http://stackoverflow.com/questions/34676553/can-google-app-engine-read-from-app-using-jxl-but-not-apache-poi/34742262#34742262

[Gagravarr via StackOverflow]

Promoting a comment to an answer - in a case like this you should explicitly tell Apache POI to open your file in read-only mode

For a .xlsx file, do that with

OPCPackage pkg = OPCPackage.open(new File("input.xlsx"), PackageAccess.READ);
XSSFWorkbook wb = new XSSFWorkbook(pkg);

For a .xls file, do that with

NPOIFSFileSystem fs = new NPOIFSFileSystem(new File("input.xls"), true);
HSSFWorkbook wb = new HSSFWorkbook(fs);

If you're using WorkbookFactory, then you can do that by passing in null for the password and setting the read-only flag with

Workbook wb = WorkbookFactory.create(new File("input.xlsx"), null, true);

In general, reading from an InputStream is always read-only, it's with Files where there's an option for read-only vs read-write

See the constructor javadocs for a little bit more details, and the WorkbookFactory one too.