We Keep Coding

Updating a file in a zip archive

I want to update a file inside a zip archive without the need to create a new archive. I am aware that it could be done by creating a new archive, coping over all other files and add the changed one in.
Here is the code to demonstrate the issue. The first section creates the initial zip archive containing one file with the content Hello world!. The second section should replace that content with Bye, bye!. The last section is unpacking the zip again so that the content can be expected:
try {
// Create the initial zip archive with the original file content
File file1 = new File(ReplaceFileInZipDemo.class.getResource("/helloworld.txt").toURI());
File zipFile = new File("output.zip");
FileOutputStream fos = new FileOutputStream(zipFile);
ZipOutputStream zipOut = new ZipOutputStream(fos);
FileInputStream fis = new FileInputStream(file1);
ZipEntry zipEntry = new ZipEntry(file1.getName());
zipOut.putNextEntry(zipEntry);
byte[] bytes = new byte[1024];
int length;
while ((length = fis.read(bytes)) >= 0) {
zipOut.write(bytes, 0, length);
}
fis.close();
zipOut.close();
fos.close();
// Replace the original file content with a different file content, updating the file.
File file2 = new File(ReplaceFileInZipDemo.class.getResource("/goodbyeworld.txt").toURI());
Path zipfile = zipFile.toPath();
FileSystem fs = FileSystems.newFileSystem(zipfile, null);
Path pathInZipfile = fs.getPath(file1.getName());
Files.copy(file2.toPath() , pathInZipfile, StandardCopyOption.REPLACE_EXISTING );
// Extract the content of the updated file
String destinationDir = System.getProperty("java.io.tmpdir");
File targetDir = new File(destinationDir);
ZipInputStream i = new ZipInputStream(new FileInputStream(zipFile));
ZipEntry entry = null;
System.out.println("Original file content:");
Files.readAllLines(file1.toPath(), StandardCharsets.UTF_8).forEach(line -> System.out.println(line));
System.out.println("Expected replaced file content");
Files.readAllLines(file2.toPath(), StandardCharsets.UTF_8).forEach(line -> System.out.println(line));
while ((entry = i.getNextEntry()) != null) {
File destFile = new File(targetDir, entry.getName());
String name = destFile.getAbsolutePath();
File f = new File(name);
try (OutputStream o = Files.newOutputStream(f.toPath())) {
IOUtils.copy(i, o);
}
System.out.println("Content of extracted file " + name);
Files.readAllLines(f.toPath(), StandardCharsets.UTF_8).forEach(line -> System.out.println(line));
}
} catch (Exception e) {
e.printStackTrace();
}
The output that I get is this:
Original file content:
Hello world!
Expected replaced file content
Bye, bye!
Content of extracted file /tmp/helloworld.txt
Hello world!
The only reason that I could imagine this is not working as expected is because the content of the replacement comes from a file with a different name than in the archive. But when adding Files.delete(pathInZipfile); to remove the original file completely it is still there.
How can I replace the content of a file in an archive with the content of another file?

Android file storage

I have a zip file in assets. On first run of app, zip file (all files and folders) gets unzipped and stored in internal storage area. The base unzipped path is getFilesDir(). Since zip also contains folders, i could not use openFileOutput as it gave an error, contains a path separator. So i have used FileOutputStream instead which is now working fine. Since FileOutputStream does not expect private flag. Are these unzipped files and folders are private to my app or can they be accessed from other apps?
Here's the code,
`public boolean unpackZip(InputStream is, String path) throws IOException {
String filename;
ZipInputStream zis = new ZipInputStream(new BufferedInputStream(is));
ZipEntry ze;
byte[] buffer = new byte[1024];
int count;
while ((ze = zis.getNextEntry()) != null) {
filename = ze.getName();
// Need to create directories if not exists, or
// it will generate an Exception...
if (ze.isDirectory()) {
File fmd = new File(path + filename);
fmd.mkdirs();
continue;
}
FileOutputStream fout = new FileOutputStream(path + filename);
while ((count = zis.read(buffer)) != -1) {
fout.write(buffer, 0, count);
}
fout.close();
zis.closeEntry();
}
zis.close();
return true;
}`

getting error while unzipping

My UnZip class does not unzip whole the file. This class is called from another activity. My zip file is saved in the main directory of the phone's internal storage. The zip file has folders and some video.
What's wrong with this unzip?
What and how should I read file from zip' decompress and unzip is the same meaning?
Thanks for your help!
public class Unzip {
private static final String INPUT_ZIP_FILE = "sdcard/downloaded_issue.zip";
private static final String OUTPUT_FOLDER = "sdcard/Atlantis/";
public static void main()
{
Unzip unZip = new Unzip();
unZip.unZipIt(INPUT_ZIP_FILE, OUTPUT_FOLDER);
}
/**
* Unzip it
* #param zipFile input zip file
* #param outputFolder zip file output folder
*/
public void unZipIt(String zipFile, String outputFolder){
byte[] buffer = new byte[1024];
try{
//create output directory is not exists
File folder = new File(OUTPUT_FOLDER);
if(!folder.exists()){
folder.mkdir();
}
//get the zip file content
ZipInputStream zis =
new ZipInputStream(new FileInputStream(zipFile));
//get the zipped file list entry
ZipEntry ze = zis.getNextEntry();
while(ze!=null){
String fileName = ze.getName();
File newFile = new File(outputFolder + File.separator + fileName);
System.out.println("file unzip : "+ newFile.getAbsoluteFile());
//create all non exists folders
//else you will hit FileNotFoundException for compressed folder
new File(newFile.getParent()).mkdirs();
FileOutputStream fos = new FileOutputStream(newFile);
int len;
while ((len = zis.read(buffer)) > 0) {
fos.write(buffer, 0, len);
}
fos.close();
if (ze.isDirectory()) {
ze = zis.getNextEntry();
}
}
zis.closeEntry();
zis.close();
System.out.println("Done");
}catch(IOException ex){
ex.printStackTrace();
}
}
}

I think your 'while' loop is broken; you're only fetching the next entry if that next entry is a directory, while I assume you're probably trying to skip the directories.
Anyway, since you create the folders for all files you encounter, you can just skip the folder entries and write the file entries. The only exception would be the creation of empty folders.
Replacing the while-loop by this code should work:
while(ze!=null){
String fileName = ze.getName();
File newFile = new File(outputFolder + File.separator + fileName);
System.out.println("file unzip : "+ newFile.getAbsoluteFile());
//create all non exists folders
//else you will hit FileNotFoundException for compressed folder
if (ze.isDirectory()) {
// create the folder
newFile.mkdirs();
}
else {
// create the parent folder and write to disk
new File(newFile.getParent()).mkdirs();
FileOutputStream fos = new FileOutputStream(newFile);
int len;
while ((len = zis.read(buffer)) > 0) {
fos.write(buffer, 0, len);
}
fos.close();
}
// get the next item
ze = zis.getNextEntry();
}

How to access a zip file into a zip file in Java

I'm trying to read .srt files that are located in zip file itself located in a zip file. I succeed to read .srt files that were in a simple zip with the extract of code below :
for (Enumeration enume = fis.entries(); enume.hasMoreElements();) {
ZipEntry entry = (ZipEntry) enume.nextElement();
fileName = entry.toString().substring(0,entry.toString().length()-4);
try {
InputStream in = fis.getInputStream(entry);
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String ext = entry.toString().substring(entry.toString().length()-4, entry.toString().length());
But now i don't know how i could get to the zip file inside the zip file.
I tried using ZipFile fis = new ZipFile(filePath) with filePath being the path of the zip file + the name of zip file inside. It didn't recognize the path so i don't know if i am clear.
Thanks.

ZipFile only works with real files, because it's intended for use as a random access mechanism which needs to be able to seek directly to specific locations in the file to read entries by name. But as VGR suggests in the comments, while you can't get random access to the zip-inside-a-zip you can use ZipInputStream, which provides strictly sequential access to the entries and works with any InputStream of zip-format data.
However, ZipInputStream has a slightly odd usage pattern compared to other streams - calling getNextEntry reads the entry metadata and positions the stream to read that entry's data, you read from the ZipInputStream until it reports EOF, then you (optionally) call closeEntry() before moving on to the next entry in the stream.
The critical point is that you must not close() the ZipInputStream until you have finished reading the final entry, so depending what you want to do with the entry data you might need to use something like the commons-io CloseShieldInputStream to guard against the stream getting closed prematurely.
try(ZipInputStream outerZip = new ZipInputStream(fis)) {
ZipEntry outerEntry = null;
while((outerEntry = outerZip.getNextEntry()) != null) {
if(outerEntry.getName().endsWith(".zip")) {
try(ZipInputStream innerZip = new ZipInputStream(
new CloseShieldInputStream(outerZip))) {
ZipEntry innerEntry = null;
while((innerEntry = innerZip.getNextEntry()) != null) {
if(innerEntry.getName().endsWith(".srt")) {
// read the data from the innerZip stream
}
}
}
}
}
}

Find the code to extract .zip files recursively:
public void extractFolder(String zipFile) throws ZipException, IOException {
System.out.println(zipFile);
int BUFFER = 2048;
File file = new File(zipFile);
ZipFile zip = new ZipFile(file);
String newPath = zipFile.substring(0, zipFile.length() - 4);
new File(newPath).mkdir();
Enumeration zipFileEntries = zip.entries();
// Process each entry
while (zipFileEntries.hasMoreElements())
{
// grab a zip file entry
ZipEntry entry = (ZipEntry) zipFileEntries.nextElement();
String currentEntry = entry.getName();
File destFile = new File(newPath, currentEntry);
//destFile = new File(newPath, destFile.getName());
File destinationParent = destFile.getParentFile();
// create the parent directory structure if needed
destinationParent.mkdirs();
if (!entry.isDirectory())
{
BufferedInputStream is = new BufferedInputStream(zip
.getInputStream(entry));
int currentByte;
// establish buffer for writing file
byte data[] = new byte[BUFFER];
// write the current file to disk
FileOutputStream fos = new FileOutputStream(destFile);
BufferedOutputStream dest = new BufferedOutputStream(fos,
BUFFER);
// read and write until last byte is encountered
while ((currentByte = is.read(data, 0, BUFFER)) != -1) {
dest.write(data, 0, currentByte);
}
dest.flush();
dest.close();
is.close();
}
if (currentEntry.endsWith(".zip"))
{
// found a zip file, try to open
extractFolder(destFile.getAbsolutePath());
}
}
}

Cannot delete zip file after unzipping?

I am facing an unusal issue.I am building a tool which is scheduled to run every 5 mins.
It will pick up the zip files from a particular directory and extract files (depending on the file name) to a destination. I am using zipentry to get each filename in zip file and then extracting as required then I back them (zip files, once I finish all the files in a zip) to a particular directory and then delete the zip file. But sometimes (not always) the zip files do not get deleted. Since I am using fileutils.forcedelete(). I am getting an exception: unable to delete file. So I changed to the code to using fileutils.forcedeleteonexit() still some files remain in the source.
Here is a sample of my code:
sourceFile=new file(zipfile);
zipFile = new ZipFile(sourceFile);
zEnum = (Enumeration<ZipEntry>) zipFile.entries();
for (int a = 0; a < zipFile.size(); a++)
{
ZipEntry zE = zEnum.nextElement();
//Function uses zip4j for extracting. No streams used.
extract(String sourceZipFile, String fileNameToExtract, String outputFolder);
}
//I tried it with finally either
zipFile.close();
//Using fileutils to copy. No streams used.
copyFile(sourceFile, backup);
FileUtils.forceDeleteOnExit(sourceFile);
There are no streams used but I am getting a lock on files sometimes (not always).
What seems to be the bug here? Is it the zip4j extraction that is causing the problem or anything else? I am using zip4j 1.3.1.

I think your problem related with OS file buffers, that sometimes are not flushed when you are trying to delete file.
Did you try to use sourceFile.deleteOnExit() instead FileUtils.forceDeleteOnExit(sourceFile)?
Also you can try to check sourceFile.canWrite before deleting (may be it may helps)
You can also try to use FileInputStream() before deleting:
FileInputStream fi = new FileInputStream(sourceFile);
fi.getFD().sync();

Use apache-commons IO's FileDeleteStrategy. Something like:
FileDeleteStrategy.FORCE.delete(file);
Update:
It should be the way IO is being handled in your application. I have written simple code which copies a zip file to a temporary zip, deflates the temporary zip and after few seconds deletes it. Here you go:
public class ZipTest {
private static String dirPath = "/home/ubuntuuser/Desktop/";
public static void main(String[] args) throws Exception {
File myzip = new File(dirPath + "content.zip");
String tempFileStr = dirPath + "content_temp.zip";
File tempFile = new File(tempFileStr);
String unzipFolderStr = dirPath + "unzip";
copyUsingChannels(myzip, tempFile);
// copyUsingStreams(myzip, tempFile);
unZip(tempFileStr, unzipFolderStr);
Thread.sleep(3000);
tempFile.delete();
}
private static void copyUsingStreams(File myzip, File tempFile)
throws IOException, FileNotFoundException {
byte[] barray = new byte[1024];
if (!tempFile.exists())
{
tempFile.createNewFile();
}
FileOutputStream fos = new FileOutputStream(tempFile);
FileInputStream fis = new FileInputStream(myzip);
int length = 0;
while ((length = fis.read(barray)) != -1)
{
fos.write(barray, 0, length);
}
fis.close();
fos.close();
}
public static void copyUsingChannels(final File srcFile, final File destFile) throws Exception
{
if (!destFile.exists())
{
destFile.createNewFile();
}
FileChannel source = new FileInputStream(srcFile).getChannel();
FileChannel destination = new FileOutputStream(destFile).getChannel();
source.transferTo(0, source.size(), destination);
source.close();
destination.close();
}
private static void unZip(String zipFile, String outputFolder) throws Exception {
byte[] buffer = new byte[1024];
File folder = new File(outputFolder);
if (!folder.exists()) {
folder.mkdir();
}
ZipInputStream zis = new ZipInputStream(new FileInputStream(zipFile));
ZipEntry ze = zis.getNextEntry();
while (ze != null) {
String fileName = ze.getName();
File newFile = new File(outputFolder + File.separator + fileName);
System.out.println("file unzip : " + newFile.getAbsoluteFile());
new File(newFile.getParent()).mkdirs();
if (ze.isDirectory())
{
newFile.mkdir();
ze = zis.getNextEntry();
continue;
}
FileOutputStream fos = new FileOutputStream(newFile);
int len;
while ((len = zis.read(buffer)) > 0) {
fos.write(buffer, 0, len);
}
fos.close();
ze = zis.getNextEntry();
}
zis.closeEntry();
zis.close();
}
}