rJava NoSuchFileException when running jar from R

Question

I'm trying to run a runnable JAR file from R, using the rJava package. This jar has to write and read some files to/from external folders, that are in the same path as the jar file itself, like this:

mypath/myjar.jar
mypath/folder1
mypath/folder2
mypath/input_file1.txt
mypath/input_file2.txt

The program works fine if I call it by opening a console in "mypath" and running the jar the following way:

java -jar myjar.jar input_file1.txt input_file2.txt false

But when I try to run this code in R, using rJava, the code crashes at some point, because it can't find neither mypath/folder1 nor mypath/folder2, even though the working directory is correctly defined as "mypath".

jinit(".",force.init=TRUE) # this starts the JVM
.jaddClassPath("myjar.jar")
jobject <- .jnew("package_name/Main")  ## call the constructor

result_java <- rJava::.jcall(obj = jobject, returnSig = "V", method = "main", c("input_file1.txt","input_file2.txt","false"))

In fact, the java program is called, it is able to actually find the input files which are also in mypath, but for some reason crashes when it tries to write to folders in mypath (such as folder1 and folder2) with the error:

Error executing task java.nio.file.NoSuchFileException: folder1/some_file.txt

I really have no idea what's going on, spent hours on this. Am I missing something really obvious here?

score 0 · Answer 1 · answered Oct 02 '17 at 06:48

When you run your code using Java, you are inside mypath and locations folder1 and folder2 are visible to your code.

Maybe, you should pass (as argument) location of directory, and instead of accessing folder1 in your Java code, you should access explicit path.

result_java <- 
   rJava::.jcall(
     obj = jobject, 
     returnSig = "V", 
     method = "main",
       c( 
         "input_file1.txt",
         "input_file2.txt",
         "false",
         "full_path_to_your_mypath_location"))

Then, inside main, you could simply open full_path_to_your_mypath_location/some_file.txt. When you start R, you probably no longer inside directory with your code. You can also try to change dir

setwd(full_path_to_your_mypath_location)

rJava NoSuchFileException when running jar from R

1 Answers1