Properly load file packaged inside .war file

Question

I have Java Web application that works with jFuzzyLogic library which uses rules.fcl file which is located at WEB-INF/rules/rules.fcl .

On my local server everything seems to work, but when I deploy war to Heroku, I get this error:

java.lang.NullPointerException
java.io.FileInputStream.<init>(FileInputStream.java:133)
java.io.FileInputStream.<init>(FileInputStream.java:96)
java.io.FileReader.<init>(FileReader.java:58)
net.sourceforge.jFuzzyLogic.FIS.load(FIS.java:143)
net.sourceforge.jFuzzyLogic.FIS.load(FIS.java:130)
com.vukstankovic.professionalorientation.Results.calculation(Results.java:119)

At my Results at line 119 I'm trying to load rules.fcl like this:

FIS fis = FIS.load(ctx.getRealPath("WEB-INF/rules/rules.fcl"));

At the begining of this method I have this annotation:

@Context ServletContext ctx;

What am I doing wrong?

Answer 1

You should be using ServletContext#getResourceAsStream which would load your files with designed path based on root level of war package:

InputStream inputStream = ctx.getResourceAsStream("/WEB-INF/rules/rules.fcl");

Then, it is up to you to use that stream and chain it to load your file content. It should be something like the follwoing if there a FIS#load method that accept InputStream as paramter:

boolean verbose = true; //Just choose your suitable value (verbose mode or not)
FIS fis = FIS.load(inputStream, verbose);

^{Just caught the method signature from this svn repo .}

Answer 2

Path passed to ServletContext.getRealPath() should start with a '/' character:

FIS fis = FIS.load(ctx.getRealPath("/WEB-INF/rules/rules.fcl"));

And also according to the javadoc :

This method returns null if the servlet container cannot translate the virtual path to a real path for any reason (such as when the content is being made available from a .war archive).

So if your .war archive is not extracted, this method won't work. Make sure your deployed .war file gets unpacked.