Load resource from Jar file : JarFile « File « Java Tutorial

1. Java Tutorial
2. File
3. JarFile

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipInputStream;


public final class JarResources {
  Hashtable htSizes = new Hashtable();
  Hashtable htJarContents = new Hashtable();
  private String jarFileName;
  public JarResources(String jarFileName) throws Exception {
    this.jarFileName = jarFileName;
    ZipFile zf = new ZipFile(jarFileName);
    Enumeration e = zf.entries();
    while (e.hasMoreElements()) {
      ZipEntry ze = (ZipEntry) e.nextElement();


      htSizes.put(ze.getName(), new Integer((int) ze.getSize()));
    }
    zf.close();

    // extract resources and put them into the hashtable.
    FileInputStream fis = new FileInputStream(jarFileName);
    BufferedInputStream bis = new BufferedInputStream(fis);
    ZipInputStream zis = new ZipInputStream(bis);
    ZipEntry ze = null;
    while ((ze = zis.getNextEntry()) != null) {
      if (ze.isDirectory()) {
        continue;
      }


      int size = (int) ze.getSize();
      // -1 means unknown size.
      if (size == -1) {
        size = ((Integer) htSizes.get(ze.getName())).intValue();
      }

      byte[] b = new byte[(int) size];
      int rb = 0;
      int chunk = 0;
      while (((int) size - rb) > 0) {
        chunk = zis.read(b, rb, (int) size - rb);
        if (chunk == -1) {
          break;
        }
        rb += chunk;
      }

      htJarContents.put(ze.getName(), b);
    }
  }

  public byte[] getResource(String name) {
    return (byte[]) htJarContents.get(name);
  }
  private String dumpZipEntry(ZipEntry ze) {
    StringBuffer sb = new StringBuffer();
    if (ze.isDirectory()) {
      sb.append("d ");
    } else {
      sb.append("f ");
    }

    if (ze.getMethod() == ZipEntry.STORED) {
      sb.append("stored   ");
    } else {
      sb.append("defalted ");
    }

    sb.append(ze.getName());
    sb.append("\t");
    sb.append("" + ze.getSize());
    if (ze.getMethod() == ZipEntry.DEFLATED) {
      sb.append("/" + ze.getCompressedSize());
    }

    return (sb.toString());
  }

  public static void main(String[] args) throws Exception {
    JarResources jr = new JarResources("a.jar");
    byte[] buff = jr.getResource("b.gif");
  }
}