FileNotFoundException while running as a jar

问题

FileInputStream fstream = new FileInputStream("abc.txt")

is throwing a FileNotFoundExceptionn while running as a jar. Why ? Normally it is able to find while running from main method.

回答1:

If your file is packaged with your jar then you should to get information using getClass().getResource(url):

FileInputStream inputStream = 
new FileInputStream(new File(getClass().getResource(/path/to/your/file/abc.txt).toURI()));

Else you need to create it always in the same path with your jar and you can get it like you do :

src/myJar.jar
src/folder/abc.txt

FileInputStream fstream = new FileInputStream("folder/abc.txt");

You can read here also :

How do I load a file from resource folder? and File loading by getClass().getResource()

回答2:

class MyClass{

    InputStream fstream = this.getClass().getResourceAsStream("abc.txt");

}

This code should be used. And the files(in this case abc.txt) should be kept , in the Object references class location. That means , this.getClass refers to the location of some folder i.e, com/myfolder/MyClass.java folder .

So we should keep the abc.txt in com/myfolder this location.

回答3:

You can use FileInputStream only when you actually have a file on the computer's filesystem. When you package your text file in the jar file for your program, it is not a file in the filesystem. It is an entry inside the jar file.

The good news is that it is even easier, in Java, to access the file this way: it is in your classpath, so you can use getResourceAsStream().

InputStream stream = getClass().getResourceAsStream("abc.txt");

If you have your classpath set up correctly, this will work regardless of whether it is a file in a directory (such as during development), or an entry in a jar file (such as when released).

回答4:

It's because your working directory will probably be different under the two environments. Try adding the line

System.out.println(new File("abc.txt").getAbsolutePath());

to see where it is actually looking for the file.

回答5:

Maybe not the most elegant but this is how you can cover all the options in Scala

def loadFile(path: String) = {
    val f = new File(path)
    if (f.exists) {
      loadFileFromPath(path)
    } else {
      val r = Try {
        val in = ClassLoader.getSystemResourceAsStream(path)
        new InputStreamReader(in)
      }.getOrElse{
        val in = getClass.getResourceAsStream(s"/$path")
        new InputStreamReader(in)
      }
      loadFileFromInputStream(r)
    }
  }

来源：https://stackoverflow.com/questions/41762124/filenotfoundexception-while-running-as-a-jar

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java

jar

filenotfoundexception