无法访问src / main / resources /下的文件

Question

I am trying to get to a file located under resources and get null :

 File propertiesFile = new File(this.getClass().getClassLoader().getResource(file).getFile());

file = Log.csv

Even if the file is directly under resource or under one of the folders under it. this.getClass().getClassLoader().getResource(file) - return null

Answer 1

this.getClass().getClassLoader().getResource(file).getFile()

capture the path till resources folder, if you have folder inside resources then you have to give that along with the file name.

for example -

resources -> folder -> test.csv

Then give file name :

String file = "folder/test.csv";

Hope this helps!

Answer 2

Resources are not real File s on the file system, but on the class path . They could be packed in a jar with an URL like "jar:file://.../xyz.jar!test.csv" . Hence use an InputStream.

InputStream in = getClass().getResourceAsStream("/test.csv");
String userHome = System.getProperty("user.home");
Path path = Paths.get(userHome, "test2.csv");
Files.copy(in, path, StandardCopyOption.REPLACE_EXISTING);

Resources should be considered read-only ; hence use them as template, initial empty file, read-only data or such.

The ClassLoader has only absolute paths under the root src/main/resources, without starting / . The Class has URLs relative to the class' package directory (but under src/main/resources), or starting with / an absolute path.