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Make sure the file resides in the project folder if you're referencing it via a relative path. If not, use the absolute path to the file with the file extension.
Make sure the glassfish server is running and hosts the file and is accessible to the public. If that's not the case, change the permissions of the file in the server's file system.
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java.io.FileNotFoundException: myfile.txt (No such file or directory)
at java.io.FileInputStream.open0(Native Method)