Reading files from Jar file recursively

JarReader.java

package xyz.com;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Reading files from jar file URL, taking care of nested jar
 * <ul>
 * <li>jar:file:/C:/Temp/single.jar!/foo</li>
 * <li>jar:file:/C:/Temp/outer.jar!/lib/inner.jar!/foo</li>
 * </ul>
 * @author Trung
 */
public class JarReader {

	private static final Logger logger =
			LoggerFactory.getLogger(JarReader.class);

	public static void read(URL jarUrl, InputStreamCallback callback) throws IOException {
		if (!"jar".equals(jarUrl.getProtocol())) {
			throw new IllegalArgumentException("Jar protocol is expected but get " + jarUrl.getProtocol());
		}
		if (callback == null) {
			throw new IllegalArgumentException("Callback must not be null");
		}
		String jarPath = jarUrl.getPath().substring(5);
		String[] paths = jarPath.split("!");
		FileInputStream jarFileInputStream = new FileInputStream(paths[0]);
		readStream(jarFileInputStream, paths[0], 1, paths, callback);
	}

	private static void readStream(InputStream jarFileInputStream, String name, int i, String[] paths, InputStreamCallback callback) throws IOException {
		if (i == paths.length) {
			callback.onFile(name, jarFileInputStream);
			return;
		}
		ZipInputStream jarInputStream = new ZipInputStream(jarFileInputStream);
		try {
			ZipEntry jarEntry = null;
			while ((jarEntry = jarInputStream.getNextEntry()) != null) {
				String jarEntryName = "/" + jarEntry.getName();
				if (!jarEntry.isDirectory() && jarEntryName.startsWith(paths[i])) {
					byte[] byteArray = copyStream(jarInputStream, jarEntry);
					logger.debug("Entry {} with size {} and data size {}", jarEntryName, jarEntry.getSize(), byteArray.length);
					readStream(new ByteArrayInputStream(byteArray), jarEntryName, i + 1, paths, callback);
				}
			}
		} finally {
			jarInputStream.close();
		}
	}

	private static byte[] copyStream(InputStream inputStream) throws IOException {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[4 * 1024];
            int n;

            while ((n = inputStream.read(buffer)) > -1) {
                baos.write(buffer, 0, n);
            }
            baos.close();

            return baos.toByteArray();
        }

	public static interface InputStreamCallback {
		void onFile(String name, InputStream is) throws IOException;
	}
}

thx for this, I really search since a long time for that 😃 👍

thx for this

copyStream can be simplified:

        private static byte[] copyStream(InputStream inputStream) throws IOException {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[4 * 1024];
            int n;

            while ((n = inputStream.read(buffer)) > -1) {
                baos.write(buffer, 0, n);
            }
            baos.close();

            return baos.toByteArray();
        }