[Class] .class.getResourceAsStream（...）在某些目录的JAR文件中使用时返回null？

Question

I have a very strange problem. It appears that loading resources from inside a JAR file sometimes works and sometimes doesn't.

The Jar file consists only of the class files, the manifest and the test.txt .

When I pack it with Eclipse, it usually works well (the contents of test.txt can be accessed) but in some directories, the Resourceproblem.class.getResourceAsStream("/test.txt") returns null - although it's the same Jar file!

For example when I double click the jar file \\\\remotecomputer\\folder\\subfolder\\test.jar the test.txt inside the jar file could not be found. But it's also sometimes (?) the case when the path name is very long and contains spaces (at least on Windows XP SP3).

Any ideas?

Sample code:

import java.io.*;

import javax.swing.*;

public class Resourceproblem {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new Resourceproblem();
            }
        });
    }

    private Resourceproblem() {
        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 500);
        frame.setLocationRelativeTo(null);
        JTextArea text = new JTextArea();
        text.setEditable(false);
        frame.add(text);
        frame.setVisible(true);

        try {
            InputStream in = Resourceproblem.class.getResourceAsStream("/test.txt");
            BufferedReader br = new BufferedReader(new InputStreamReader(in));
            String line = br.readLine();
            br.close();
            in.close();
            text.setText(line);
        } catch(Exception ex) {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            ex.printStackTrace(pw);
            pw.flush();
            String s = sw.toString();
            pw.close();
            ex.printStackTrace();
            text.setText(s);
        }
    }
}

test.txt ist just a text file with a line for checking if the loading was successful.

Answer 1

I have an idea, but I have little confidence that I know what your problem is.

I used eclipse to create a jar file from your example source several times; I stored the jar file in c:\\local and in c:\\local\\one\\two three\\four, using Win7.

I am unfamiliar with the use of "/" at the front of the resource filename in the getResourceAsStream() call. Your sample program worked in each case either with or without the "/", but I would recommend removing it and seeing if that solves your problem. The file, in that case, goes in the same directory as the class that is accessing it.

I would have thought that the "/" would cause the program to look for the file at the root directory of the file system, but that doesn't seem to happen...