为什么我无法从资源中获取文件？

Question

Why can't I get a file from resources?

URL resource = getClass().getClassLoader().getResource("input data/logic test.csv");
    System.out.println("Found "+resource);

    CSVParser parser = new CSVParserBuilder().withSeparator(';').build();
    CSVReader reader = new CSVReaderBuilder(new FileReader(resource.getFile())).withSkipLines(1).withCSVParser(parser).build();

Console output:

Found file:/home/alexandr/Repos/OTUS/first_home_work/target/classes/input%20data/logic%20test.csv 

Exception in thread "main" java.io.FileNotFoundException: /home/alexandr/Repos/OTUS/first_home_work/target/classes/input%20data/logic%20test.csv (Нет такого файла или каталога)

Answer 1

There is an inherent logic problem with this line:

CSVReader reader = new CSVReaderBuilder(
    new FileReader(resource.getFile()))..

Once the CSV is part of a Jar, it will no longer be accessible as a File object. But something like this should work directly for the URL.

CSVReader reader = new CSVReaderBuilder(
    new InputStreamReader(resource.openStream()))..

change space for _ in directory name and file name, and working

This will only work while the resource is not in a Jar file.

Answer 2

It's:

try (InputStream raw = ClassThisIn.class.getResourceAsStream(""input data/logic test.csv")) {
    InputStreamReader isr = new InputStreamReader(raw, StandardCharsets.UTF_8);
    BufferedReader br = new BufferedReader(isr);
    // now use br as if it was your filereader.
}

This addresses many issues:

1. Still works regardless of how you're running it: Your snippet only works if running as straight class files (vs., say, in a jar), and doesn't work if spaces are involved.
2. Still works even if your class is subclassed ( getClass().getClassLoader().getResource won't, which is why you should not do that).
3. Still works even if the platform local charset encoding is weird (the snippet in this answer is explicit about it. That's always a good idea).
4. Doesn't have a resource leak. Your code never safely closes the reader you open. If you open resources, either do so in a try-with-resources construct, or, store the resource in a field and implement AutoClosable.

Answer 3

我在目录名和文件名中更改了 _ 的空间，然后工作.... omg。

Answer 4

The answer is in your console output - the file was simply not found. I would try the same code you have written, but use a file without spaces in it - and see if the file is still not found.