Exclude extensions in filename filter in Java

Question

My Controller method (which has a method to list the files, from a path mentioned in the property file, on JSP)

private String[] getFileListing(String servers) throws IOException {
        Properties prop = new Properties();
        String propFileName = "config.properties";
        InputStream input = getClass().getClassLoader().getResourceAsStream(propFileName);

        prop.load(input);

        if (servers.equals("MS1")) {
            File f = new File(prop.getProperty("path.MS1"));
            String[] list = f.list(new FilenameFilter() {
                public boolean accept(File dir, String name) {
                    return name.toLowerCase().endsWith(".txt")||name.endsWith(".log");
                }
            });

            return list;

        } else {
            File f = new File(prop.getProperty("path.MS2"));
            String[] list = f.list(new FilenameFilter() {
                public boolean accept(File dir, String name) {
                    return name.toLowerCase().endsWith(".txt")||name.endsWith(".log");
                }
            });

            return list;
        }

    }

I want to display the log files with common extensions like- .txt or .log But the system creates files with .1 .2 .3 extensions also.

Is there a clear method to include all these file-type extensions as well?
If not, then how to display all file "excluding" some file types in the directory. (I would want to exclude some other system generated files from the directory).

Thanks!

To exclude a file type, why not just use `!name.toLowerCase().endsWith("...")`? — DodgyCodeException, May 15 '18 at 10:34

Eby Jacob · Answer 1 · 2018-05-15T13:25:12.317

0

You can return the files which don't have specific file extensions.

private String[] getFileListing(String servers) throws IOException {
        Properties prop = new Properties();
        String propFileName = "config.properties";
        InputStream input = getClass().getClassLoader().getResourceAsStream(propFileName);

        prop.load(input);

        if (servers.equals("MS1")) {
            File f = new File(prop.getProperty("path.MS1"));
            String[] list = f.list(new FilenameFilter() {
                public boolean accept(File dir) {
                    return ! (dir.toLowerCase().endsWith(".gz")||dir.endsWith(".sh")) && dir.isFile();
                }
            });

            return list;

        } else {
            File f = new File(prop.getProperty("path.MS2"));
            String[] list = f.list(new FilenameFilter() {
                public boolean accept(File dir) {
                    return ! (dir.toLowerCase().endsWith(".gz")||dir.endsWith(".sh")) && dir.isFile();
                }
            });

            return list;
        }
    }

edited May 15 '18 at 13:25

answered May 15 '18 at 10:59

Eby Jacob

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Missing parentheses around the 'OR'ed expressions? – DodgyCodeException May 15 '18 at 11:15
updated the answer based on your comment, Thanks for bringing that up. – Eby Jacob May 15 '18 at 12:11
Thanks @EbyJacob. I am able to make this work, but I get folders also along with all the files. How to exclude them in my code? – Niharika Pandey May 15 '18 at 13:04
Hi Niharika, have updated to code to exclude the subdirectories in the folder. check if this works – Eby Jacob May 15 '18 at 13:25

score 0 · Accepted Answer · answered May 15 '18 at 11:34

You could do a couple of things with this code, i'd honestly just refactor this quite a bit and have your whitelist be an ArrayList of extensions.

For example:

private String[] getFileListing(String servers) throws IOException {
    List<String> allowedExtensions = Arrays.asList("log txt".split(" "));
    Properties prop = new Properties();
    String propFileName = "config.properties";
    InputStream input = getClass().getClassLoader().getResourceAsStream(propFileName);
    prop.load(input);

    File f = new File(prop.getProperty("path." + servers));
    String[] list = f.list(new FilenameFilter() {
        public boolean accept(File dir, String name) {
            return allowedExtensions.contains(name.substring(name.lastIndexOf(".") + 1, name.length()));
        }
    });
    return list;
}

But, that being said, there are a couple of other things in your code that could be optimized, for example, as i changed above, you're checking if a servers string equals something, then loading it, i assumed because you only have MS1 and MS2, that being said, if the intention was that it loads MS2 always on every servers parameter except for MS1, you could do that like so:

private String[] getFileListing(String servers) throws IOException {
    List<String> allowedExtensions = Arrays.asList("log txt".split(" "));
    Properties prop = new Properties();
    String propFileName = "config.properties";
    InputStream input = getClass().getClassLoader().getResourceAsStream(propFileName);
    prop.load(input);

    File f = new File(prop.getProperty("path.ms2"));
    if(servers.equals("MS1")){
        f = new File(prop.getProperty("path." + servers));
    }
    String[] list = f.list(new FilenameFilter() {
        public boolean accept(File dir, String name) {
            return allowedExtensions.contains(name.substring(name.lastIndexOf(".") + 1, name.length()));
        }
    });
    return list;
}

If you want to support other things, like .log.1, or .log.2, this approach wouldn't work, but you could invert it and make the list a blacklist of extensions, or use regex to match filenames, for example, for any file ending in .log or .log.

this regex will match any filename following what appear to be your whitelist conditions:

^.+(.log|.txt)(.\d)?$

You can see this with some exmple matches here

Thank you @zack6849. I got it! – Niharika Pandey May 15 '18 at 13:17 — Niharika Pandey, May 15 '18 at 13:17

Exclude extensions in filename filter in Java

2 Answers2