How to read a file from a java class, both are in the same jar

问题

I have following structure in jar

myjar.jar -> com -> MYProgram.class
       -> file.txt

In MYProgram i am trying to do:

getClass().getResourceAsStream("../file.txt")

I am getting NullpointerException when i try to read the inputstream..

Where is it going wrong ?

回答1:

Either use

getClass().getResourceAsStream("/file.txt")

getClass().getClassLoader().getResourceAsStream("file.txt")

(ClassLoader.getResourceAsStream always takes an "absolute" resource name.)

I don't believe navigating up the "directory hierarchy" works in getResourceAsStream - the path either has to be relative to the given class but without navigating back up the tree, or it has to be absolute to start with.

回答2:

Try the absolute path:

getClass().getResourceAsStream("/file.txt")

The Javadoc for getResourceAsStream says:

If the name begins with a '/' ('\u002f'), then the absolute name of the resource is the portion of the name following the '/'.
Otherwise, the absolute name is of the following form:
    modified_package_name/name
Where the modified_package_name is the package name of this object with '/' substituted for '.' ('\u002e').

This would turn your path into this absolute path:

/com/../file.txt

I don't think the .. notation is respected. It literally looks for the above absolute path.

来源：https://stackoverflow.com/questions/5476530/how-to-read-a-file-from-a-java-class-both-are-in-the-same-jar

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