使用类路径在Java中加载CSV

Question

How to load csv file using classpath? Before this I tried loading file using FileReader which works fine when running locally but when deployed into external server throws exceptions like FileNotFound. Below code works in local, but when deployed the jar on tomcat folder www/[jar] throws this exception Unfortunately, I cannot provide the original code. here is the gist:

BufferedReader br = new BufferedReader(new FileReader("src/SSR.csv"));
    while ((line = br.readLine()) != null) {
        // use comma as separator
        String[] cols = line.split(",");
        map.put(cols[1],cols[0]); 

Answer 1

There are two things you should consider here

1. As our colleagues have already stated, when the code runs in jar and you want to load a classpath resource you cannot go with FileReader approach that you've stated.

Your current code assumes that the CSV is somewhere in FileSystem outside the artifact, which is probably not true, so it just won't find the file.

The correct approach here will be using getClass().getResourceAsStream() / getClass().getClassLoader().getResourceAsStream()

2. CSV files can be complicated although their structure looks dead simple. So if you work on a real-life project and not on some kind of homework for studying purposes, I strongly suggest you use 3rdparty libraries for working with CSV:

   • Open CSV
   • Super CSV
   • Commons-CSV

...to name a few

Answer 2

Since you tagged the question with spring I would like to point you to the Resource Implementations that the Spring Framework provide. The documentation can be found under:

Spring Support for Resources

For your csv file something along the lines of

Resource csv = context.getResource("classpath:some/resource/path/my.csv");
InputStream inputstream = csv.getInputStream();

should be a starting point. The Resource Interface provides a

File getFile() throws IOException;

method, but this does only work when the File resides in the filesystem. So for your case you should use the approach with the inputstream I think.

EDIT: Here you can find another answer with the use of the ClassPathResource https://stackoverflow.com/a/44412189/7634201