How to get file directory structure as JSON in Java?

Question

What i am trying to accomplish is pretty straight forward. I want to create a method, which accept a root directory param as input, and return the file folder structure comes under input directory as JSON data. I started from the code below;

public class dirscan {
    public static void main (String args[]) {
        displayIt(new File("D:\MyDir"));
    }

    public static void displayIt(File node) {
        System.out.println(node.getAbsoluteFile());
        if (node.isDirectory()) {
            String[] subNote = node.list();
            for (String filename : subNote) {
                displayIt(new File(node, filename));
            }
        }
    }
}

It prints directory and file list. I implemented an array list, and modified it as below;

public class DirScan {
    static List<String> allList = new ArrayList<String>();

    public static void main(String args[]) {
        List<String> mylist = displayIt(new File("D:\Books"));
        for (String filename : mylist) {
            System.out.println(filename);
        }
    }

    public static List<String> displayIt(File node) {
        allList.add(node.getAbsoluteFile().toString());
        if (node.isDirectory()) {
            String[] subNote = node.list();
            for (String filename : subNote) {
                displayIt(new File(node, filename));
            }
        }
        return allList;
    }
}

It also does the same. What i am trying to accomplish is, to return the directory listing as JSON, something like an array, array inside array solution. Is this possible?

Answer 1

If you would like to create a JSON it is better to work with Objects, so a possible solution can be:

This is a class representing a file.

public class CustomFile {

    private String name;

    public CustomFile(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "CustomFile [name=" + name + "]";
    }

}

This is a class representing a folder.

public class CustomFolder {

    private String name;

    List<CustomFile> files;

    List<CustomFolder> folders;

    public CustomFolder(String name) {
        files = new ArrayList<>();
        folders = new ArrayList<>();
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<CustomFile> getFiles() {
        return files;
    }

    public void addFile(CustomFile file) {
        this.files.add(file);
    }

    public List<CustomFolder> getFolders() {
        return folders;
    }

    public void addFolder(CustomFolder folder) {
        this.folders.add(folder);
    }

    @Override
    public String toString() {
        return "CustomFolder [name=" + name + ", files=" + files + ", folders=" + folders + "]";
}

And the main functionality:

public class Main {
    static List<String> allList = new ArrayList<String>();

    public static void main(String[] args) throws IOException {
        CustomFolder parentFolder = new CustomFolder("path/to/folder");
        CustomFolder mylist = displayIt(parentFolder);
        ObjectMapper mapper = new ObjectMapper();
        System.out.println(mapper.writeValueAsString(mylist));
    }

    public static CustomFolder displayIt(CustomFolder parentFolder) throws IOException {
        File node = new File(parentFolder.getName());
        if (node.isDirectory()) {
            String[] subNote = node.list();
            for (String filename : subNote) {
                String path = node + "\\" + filename;
                if (new File(path).isDirectory()) {
                    CustomFolder folder = new CustomFolder(path);
                    parentFolder.addFolder(folder);
                    displayIt(folder);
                } else {
                    parentFolder.addFile(new CustomFile(path));
                }
            }
        }
        return parentFolder;
    }

}

For the JSON you need to include the jackson-mapper-asl artifact.

You should check it carefully before add to your program because i didn't test it much, but you can get the feeling.