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    <p>I wrote some code to read files from zips as if they were virtual folders, you're welcome to take a look at this, and get an idea of how it works. Now, when you say "without decompressing" that's not possible, but I assume you mean "without decompressing it to disk". This code does decompress it, but it does it in memory, not on disk.</p> <pre class="lang-java prettyprint-override"><code>import java.io.*; import java.util.Deque; import java.util.LinkedList; import java.util.logging.Level; import java.util.logging.Logger; import java.util.zip.ZipEntry; import java.util.zip.ZipException; import java.util.zip.ZipFile; import java.util.zip.ZipInputStream; /** * Allows read operations to happen transparently on a zip file, as if it were a * folder. Nested zips are also supported. All operations are read only. * Operations on a ZipReader with a path in an actual zip are expensive, so it's * good to keep in mind this when using the reader, you'll have to balance * between memory usage (caching) or CPU use (re-reading as needed). */ public class ZipReader { /** * The top level zip file, which represents the actual file on the file system. */ private final File topZip; /** * The chain of Files that this file represents. */ private final Deque&lt;File&gt; chainedPath; /** * The actual file object. */ private final File file; /** * Whether or not we have to dig down into the zip, or if * we can use trivial file operations. */ private final boolean isZipped; /** * Creates a new ZipReader object, which can be used to read from a zip * file, as if the zip files were simple directories. All files are checked * to see if they are a zip. * * &lt;p&gt;{@code new ZipReader(new File("path/to/container.zip/with/nested.zip/file.txt"));}&lt;/p&gt; * * * @param file The path to the internal file. This needn't exist, according * to File, as the zip file won't appear as a directory to other classes. * This constructor will however throw a FileNotFoundException if it * determines that the file doesn't exist. */ public ZipReader(File file){ chainedPath = new LinkedList&lt;File&gt;(); this.file = file; //make sure file is absolute file = file.getAbsoluteFile(); //We need to walk up the parents, putting those files onto the stack which are valid Zips File f = file; chainedPath.addFirst(f); //Gotta add the file itself to the path for everything to work File tempTopZip = null; while ((f = f.getParentFile()) != null) { chainedPath.addFirst(f); try { //If this works, we'll know we have our top zip file. Everything else will have //to be in memory, so we'll start with this if we have to dig deeper. if (tempTopZip == null) { ZipFile zf = new ZipFile(f); tempTopZip = f; } } catch (ZipException ex) { //This is fine, it's just not a zip file } catch (IOException ex) { Logger.getLogger(ZipReader.class.getName()).log(Level.SEVERE, null, ex); } } //If it's not a zipped file, this will make operations easier to deal with, //so let's save that information isZipped = tempTopZip != null; if(isZipped){ topZip = tempTopZip; } else { topZip = file; } } /** * Returns if this file exists or not. Note this is a non-trivial operation. * * @return */ public boolean exists(){ if(!topZip.exists()){ return false; //Don't bother trying } try{ getInputStream().close(); return true; } catch(IOException e){ return false; } } /** * Returns true if this file is read accessible. Note that if the file is a zip, * the permissions are checked on the topmost zip file. * @return */ public boolean canRead(){ return topZip.canRead(); } /** * Returns true if this file has write permissions. Note that if the file is nested * in a zip, then this will always return false * @return */ public boolean canWrite(){ if(isZipped){ return false; } else { return topZip.canWrite(); } } /* * This function recurses down into a zip file, ultimately returning the InputStream for the file, * or throwing exceptions if it can't be found. */ private InputStream getFile(Deque&lt;File&gt; fullChain, String zipName, final ZipInputStream zis) throws FileNotFoundException, IOException { ZipEntry entry; InputStream zipReader = new InputStream() { @Override public int read() throws IOException { if (zis.available() &gt; 0) { return zis.read(); } else { return -1; } } @Override public void close() throws IOException { zis.close(); } }; boolean isZip = false; while ((entry = zis.getNextEntry()) != null) { //This is at least a zip file isZip = true; Deque&lt;File&gt; chain = new LinkedList&lt;File&gt;(fullChain); File chainFile = null; while ((chainFile = chain.pollFirst()) != null) { if (chainFile.equals(new File(zipName + File.separator + entry.getName()))) { //We found it. Now, chainFile is one that is in our tree //We have to do some further analyzation on it break; } } if (chainFile == null) { //It's not in the chain at all, which means we don't care about it at all. continue; } if (chain.isEmpty()) { //It was the last file in the chain, so no point in looking at it at all. //If it was a zip or not, it doesn't matter, because this is the file they //specified, precisely. Read it out, and return it. return zipReader; } //It's a single file, it's in the chain, and the chain isn't finished, so that //must mean it's a container (or it's being used as one, anyways). Let's attempt to recurse. ZipInputStream inner = new ZipInputStream(zipReader); return getFile(fullChain, zipName + File.separator + entry.getName(), inner); } //If we get down here, it means either we recursed into not-a-zip file, or //the file was otherwise not found if (isZip) { //if this is the terminal node in the chain, it's due to a file not found. throw new FileNotFoundException(zipName + " could not be found!"); } else { //if not, it's due to this not being a zip file throw new IOException(zipName + " is not a zip file!"); } } /** * Returns a raw input stream for this file. If you just need the string contents, * it would probably be easer to use getFileContents instead, however, this method * is necessary for accessing binary files. * @return An InputStream that will read the specified file * @throws FileNotFoundException If the file is not found * @throws IOException If you specify a file that isn't a zip file as if it were a folder */ public InputStream getInputStream() throws FileNotFoundException, IOException { if (!isZipped) { return new FileInputStream(file); } else { return getFile(chainedPath, topZip.getAbsolutePath(), new ZipInputStream(new FileInputStream(topZip))); } } /** * If the file is a simple text file, this function is your best option. It returns * the contents of the file as a string. * @return * @throws FileNotFoundException If the file is not found * @throws IOException If you specify a file that isn't a zip file as if it were a folder */ public String getFileContents() throws FileNotFoundException, IOException { if (!isZipped) { return FileUtility.read(file); } else { return getStringFromInputStream(getInputStream()); } } /* * Converts an input stream into a string */ private String getStringFromInputStream(InputStream is) throws IOException { BufferedReader din = new BufferedReader(new InputStreamReader(is)); StringBuilder sb = new StringBuilder(); try { String line; while ((line = din.readLine()) != null) { sb.append(line).append("\n"); } } catch (IOException ex) { throw ex; } finally { try { is.close(); } catch (Exception ex) { } } return sb.toString(); } /** * Delegates the equals check to the underlying File object. * @param obj * @return */ @Override public boolean equals(Object obj) { if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final ZipReader other = (ZipReader) obj; return other.file.equals(this.file); } /** * Delegates the hashCode to the underlying File object. * @return */ @Override public int hashCode() { return file.hashCode(); } } </code></pre>
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    1. POJava: searching inside zips inside zips
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