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Getting resources for Java projects has always been fairly confusing to me, as the documentation doesn't explain it very well in my opinion, and I end up having to re-learn it every time I need to use it in a project. Most recently, using JavaFX, I was trying to load an image. The constructor requires a string representing the file path. I had come up with a very hacky method of doing this in the past, but I recently came across this StackOverflow post, and the accepted answer shows a very simple way of referencing the top level of the Eclipse project so that I can access source folders in the build path and easily locate my image files.

Is there a name for this particular delimeter? Are there other delimeters like it? Would there be problems using this notation when running this code in an executable JAR?

Any information would be greatly appreciated. And if this isn't the best way to approach this and someone could give me an adequate, simple explanation on how to do this in the future or a link to an article that explains it well, that would be great.

Darin Beaudreau
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2 Answers2

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You can get resources using a relative path or an absolute path. Relative paths start from the "working directory", which is the directory your application runs from. An absolute path is unambiguous. The working directory is checked before the classpath. This is what is used in places like 

new File(filepath).

When you run Java, there is also the classpath to consider. Another way some people look for resources is 

ClassLoader.getResource(String)

and 

ClassLoader.getResourceAsStream(String)

The ClassLoader can accept the String as a relative path and will check each location along the classpath. https://docs.oracle.com/javase/7/docs/api/java/lang/ClassLoader.html#getResourceAsStream(java.lang.String)

People get results by putting their files within the src folder because that usually gets copied over to the place where the class files are generated, which is included on the classpath. The "top level" that you speak of is the working directory. Eclipse sets the working directory to the project root by default.

ProgrammersBlock
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The relevant wikipedia page covers the file: scheme nicely.

But we live in a messy world, and various pieces of software may conform to older standards, or not conform completely with any standards, or may include support for alternate syntaxes. Understanding the correct syntax to use with a particular software system is unfortunately not always straightforward.

cybersam
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  • But in this case, the path didn't resolve to the C:\ drive. It referred to the project root (parent of the src folder in Eclipse projects). So with "file:res/images/etc.png", and with the "res" folder existing in the same directory as the src folder, it would get the image from the res folder. Or am I not understanding the Wiki entry? – Darin Beaudreau Jun 30 '17 at 01:37
  • Actually, it didn't refer to "the project root" - it refers to "the current directory for the process" - and your IDE just happens to set the current directory to the project root. But no such guarantee when you start the application by hand from while you are in another directory. – Erwin Bolwidt Jun 30 '17 at 01:44
  • So this would be a bad idea for an executable JAR, then? – Darin Beaudreau Jun 30 '17 at 01:46
  • I was really talking about using the "file:" scheme in general. But, with respect to relative path URIs, that is not always supported by whatever software you are using, or if it is supported the "base path" may not be the "obvious" one. Again, I am talking in general. – cybersam Jun 30 '17 at 01:47