Java Creating ZIP file system and Copying and Writing into It #java #filesystem #streams #buffered #files #io

file1.txt

ABCDEFGHIJKLMNOPQRSTUVWXYZ

Main.java

package com.jwhh;

import java.io.BufferedWriter;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.Charset;
import java.nio.file.*;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class Main {

    public static void main(String[] args) {
        String[] data = {
                "Line 1",
                "Line 2 2",
                "Line 3 3 3",
                "Line 4 4 4 4",
                "Line 5 5 5 5 5"
        };

        try (FileSystem zipFs = openZip(Paths.get("myData.zip"))) {
            copyToZip(zipFs);
            writeToFileInZip1(zipFs, data);
            writeToFileInZip2(zipFs, data);
        } catch (Exception e) {
            System.out.println(e.getClass().getSimpleName() + " - " + e.getMessage());
        }
    }

    /**
     * Creates a ZIP file system (Specialized File System, not default)
     *
     * @param zipPath Path instance representing the ZIP file
     * @return custom ZIP FileSystem
     * @throws IOException
     * @throws URISyntaxException
     */
    private static FileSystem openZip(Path zipPath) throws IOException, URISyntaxException {
        // Create properties for file system provider
        Map<String, String> providerProps = new HashMap<>();
        providerProps.put("create", "true");

        // Identify file systems by creating a URI
        // ZIP using a scheme of jar:file
        URI zipUri = new URI("jar:file", zipPath.toUri().getPath(), null);

        // Create FileSystem
        return FileSystems.newFileSystem(zipUri, providerProps);
    }

    private static void copyToZip(FileSystem zipFs) throws IOException {
        // Get path from default file system of source file (shorthand)
        Path sourceFile = Paths.get("file1.txt");

        // Longhand way of getting a path within the default file system
        // Path sourceFile = FileSystems.getDefault().getPath("file1.txt");

        // Create a path within our custom file system for the destination file
        Path destFile = zipFs.getPath("/file1Copied.txt");

        Files.copy(sourceFile, destFile, StandardCopyOption.REPLACE_EXISTING);
    }

    /**
     * Traditional way to write into a file. Create BufferedWriter from Files factory method,
     * iterate through data and write into it line by line
     * @param zipFs Custom file system
     * @param data Array of string data
     * @throws IOException
     */
    private static void writeToFileInZip1(FileSystem zipFs, String[] data) throws IOException {
        try (BufferedWriter writer = Files.newBufferedWriter(zipFs.getPath("/newFile1.txt"), StandardOpenOption.CREATE)) {
            for (String d : data) {
                writer.write(d);
                writer.newLine();
            }
        }
    }

    /**
     * Convenience way of writing into a file. Specify path, iterable object (a list), default charset
     * and options for how file is opened or created
     * @param zipFs Custom file system
     * @param data Array of string data
     * @throws IOException
     */
    private static void writeToFileInZip2(FileSystem zipFs, String[] data) throws IOException {
        Files.write(zipFs.getPath("/newFile2.txt"), Arrays.asList(data), Charset.defaultCharset(), StandardOpenOption.CREATE);
    }

}