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Extracting files with zip4j is temporary. (Extracted for reading, but not displayed in the cache file)

I work with zip4j and do packaging and extraction, but I wonder how easy it is to extract the file without putting the files in the cache.

Here is the code I found in another thread:

public static void main() { String source = "C:\\Users\\gamecaching\\Cache.zip"; String destination = "C:\\Users\\gamecaching\\"; String password = "mypassword"; try { ZipFile zipFile = new ZipFile(source); if (zipFile.isEncrypted()) { zipFile.setPassword(password); } zipFile.extractAll(destination); } catch (ZipException e) { e.printStackTrace(); } }

How to get it only for extraction while the program is running (& & extracted files that do not appear in the directory) and delete it after the program exits.

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4 answers

After creating the zipfile

 ZipFile zipFile = new ZipFile(source);

you can scroll through each file in a zip file as follows:

 ArrayList fileHeaderList = zipFile.getFileHeaders();

For each ZipFile:

 for (int i = 0; i < fileHeaderList.size(); i++) { FileHeader fileHeader = (FileHeader)fileHeaderList.get(i);

Then you can get inputStream by doing this

 is = zipFile.getInputStream(fileHeader);

You now have an InputStream to read.

A more detailed example of working with streams is given below (taken from the Zip4j sample package .) Although this example is still written to a file, it demonstrates the use of streams with a zip file. I suggest looking at a few examples in the examples package.

 import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import java.util.List; import net.lingala.zip4j.core.ZipFile; import net.lingala.zip4j.exception.ZipException; import net.lingala.zip4j.io.ZipInputStream; import net.lingala.zip4j.model.FileHeader; import net.lingala.zip4j.unzip.UnzipUtil; /** * Example demonstrating the use of InputStreams to extract files from the * ZipFile */ public class ExtractAllFilesWithInputStreams { private final int BUFF_SIZE = 4096; public ExtractAllFilesWithInputStreams() { ZipInputStream is = null; OutputStream os = null; try { // Initiate the ZipFile ZipFile zipFile = new ZipFile( "C:\\ZipTest\\ExtractAllFilesWithInputStreams.zip"); String destinationPath = "c:\\ZipTest"; // If zip file is password protected then set the password if (zipFile.isEncrypted()) { zipFile.setPassword("password"); } // Get a list of FileHeader. FileHeader is the header information // for all the files in the ZipFile List fileHeaderList = zipFile.getFileHeaders(); // Loop through all the fileHeaders for (int i = 0; i < fileHeaderList.size(); i++) { FileHeader fileHeader = (FileHeader) fileHeaderList.get(i); if (fileHeader != null) { // Build the output file String outFilePath = destinationPath + System.getProperty("file.separator") + fileHeader.getFileName(); File outFile = new File(outFilePath); // Checks if the file is a directory if (fileHeader.isDirectory()) { // This functionality is up to your requirements // For now I create the directory outFile.mkdirs(); continue; } // Check if the directories(including parent directories) // in the output file path exists File parentDir = outFile.getParentFile(); if (!parentDir.exists()) { parentDir.mkdirs(); } // Get the InputStream from the ZipFile is = zipFile.getInputStream(fileHeader); // Initialize the output stream os = new FileOutputStream(outFile); int readLen = -1; byte[] buff = new byte[BUFF_SIZE]; // Loop until End of File and write the contents to the // output stream while ((readLen = is.read(buff)) != -1) { os.write(buff, 0, readLen); } // Please have a look into this method for some important // comments closeFileHandlers(is, os); // To restore File attributes (ex: last modified file time, // read only flag, etc) of the extracted file, a utility // class can be used as shown below UnzipUtil.applyFileAttributes(fileHeader, outFile); System.out.println("Done extracting: " + fileHeader.getFileName()); } else { System.err.println("fileheader is null. Shouldn't be here"); } } } catch (ZipException e) { e.printStackTrace(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } finally { try { closeFileHandlers(is, os); } catch (IOException e) { e.printStackTrace(); } } } private void closeFileHandlers(ZipInputStream is, OutputStream os) throws IOException { // Close output stream if (os != null) { os.close(); os = null; } // Closing inputstream also checks for CRC of the the just extracted // file. If CRC check has to be skipped (for ex: to cancel the unzip // operation, etc) use method is.close(boolean skipCRCCheck) and set the // flag, skipCRCCheck to false // NOTE: It is recommended to close outputStream first because Zip4j // throws an exception if CRC check fails if (is != null) { is.close(); is = null; } } public static void main(String[] args) { new ExtractAllFilesWithInputStreams(); } }
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example obtained from ExtractAllFilesWithInputStreams:

 import java.io.BufferedInputStream; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.util.HashMap; import java.util.List; import java.util.Map; import net.lingala.zip4j.core.ZipFile; import net.lingala.zip4j.exception.ZipException; import net.lingala.zip4j.io.ZipInputStream; import net.lingala.zip4j.model.FileHeader; public class StackoverFlow18974389 { public static void main(String[] args) { Map<String, InputStream> inMemoryFiles = new HashMap<>(); try { ZipFile zipFile = new ZipFile("test.zip"); List fileHeaderList = zipFile.getFileHeaders(); for (int i = 0; i < fileHeaderList.size(); i++) { FileHeader fileHeader = (FileHeader) fileHeaderList.get(i); ZipInputStream is = zipFile.getInputStream(fileHeader); int uncompressedSize = (int) fileHeader.getUncompressedSize(); OutputStream os = new ByteArrayOutputStream(uncompressedSize); int bytesRead; byte[] buffer = new byte[4096]; while ((bytesRead = is.read(buffer)) != -1) { os.write(buffer, 0, bytesRead); } byte[] uncompressedBytes = ((ByteArrayOutputStream) os).toByteArray(); inMemoryFiles.put(fileHeader.getFileName(), new ByteArrayInputStream(uncompressedBytes)); is.close(); } } catch (ZipException | IOException ex) { ex.printStackTrace(System.err); } // very simple example how to access the files from the map for (String fileName : inMemoryFiles.keySet()) { System.out.print("in memory file: " + fileName); InputStream is = new BufferedInputStream(inMemoryFiles.get(fileName)); long length = 0; try { while (is.read() != -1) { length++; } } catch (IOException ex) { ex.printStackTrace(System.err); } System.out.println(" size. " + length); } } }
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To read a specific zip file entry, use: zipFile.getInputStream(FileHeader) . To read all entries:

 for (FileHeader entry: zipFile:getFileHeaders()){ zipFile.getInputStream(FileHeader); }
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When I did a Google search in the "trial zip file zip4j" I got into this thread, so I decided to use existing examples for people to create a method for checking zip files. Maybe this will be useful:

 import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileNotFoundException; import java.io.IOException; import java.io.OutputStream; import java.util.List; import net.lingala.zip4j.core.ZipFile; import net.lingala.zip4j.exception.ZipException; import net.lingala.zip4j.io.ZipInputStream; import net.lingala.zip4j.model.FileHeader; import org.apache.commons.io.output.NullOutputStream; /** * Example demonstrating testing Zip files using net.lingala.zip4j * * Changes: * - Created static method testZipFile * - Uses Buffered IO * - Uses Apache Commons' NullOutputStream() for /dev/null * - Uses enhanced for loop * - Skip CRC check * - Removed unapplicable code */ public class Zip4jTestZipFile { public static void main(String[] args) { File zipfile = new File("D:\\JDeveloper\\mywork\\Gas_Market_Systems\\GMS-FLISTCopy\\test\\inetpub\\tmp.lem\\FLIST_COUNTRYNWO_20140411.zip"); testZipFile(zipfile); } /* Adapted from SrikanthLingala answer (http://stackoverflow.com/a/18974782/1213722) */ public static void testZipFile(File zipfile) { ZipInputStream is = null; OutputStream os = new NullOutputStream(); // org.apache.commons.io.output.NullOutputStream /* Buffered IO */ BufferedInputStream bis = null; BufferedOutputStream bos = new BufferedOutputStream(os); try { // Initiate the ZipFile ZipFile zipFile = new ZipFile(zipfile); // If zip file is password protected then set the password if (zipFile.isEncrypted()) { zipFile.setPassword("password"); } // Get a list of FileHeader. FileHeader is the header information // for all the files in the ZipFile List<FileHeader> fileHeaderList = zipFile.getFileHeaders(); // Loop through all the fileHeaders for (FileHeader fileHeader : fileHeaderList) { if (fileHeader != null) { // Removed: Build the output file // Removed: directory checks // Removed: parent directory checks // Get the InputStream from the ZipFile is = zipFile.getInputStream(fileHeader); bis = new BufferedInputStream(is); // Removed: Initialize the output stream int readLen = -1; // Loop until End of File and write the contents to the // output stream while ((readLen = bis.read()) != -1) { bos.write(readLen); } // Please have a look into this method for some important // comments closeFileHandlers(is, os); // Removed: restore File attributes System.out.println("Done testing: " + fileHeader.getFileName()); } else { System.err.println("fileheader is null. Shouldn't be here"); } } } catch (ZipException e) { e.printStackTrace(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } finally { try { closeFileHandlers(is, os); } catch (IOException e) { e.printStackTrace(); } } } private static void closeFileHandlers(ZipInputStream is, OutputStream os) throws IOException { // Close output stream if (os != null) { os.close(); os = null; } // Closing inputstream also checks for CRC of the the just extracted // file. If CRC check has to be skipped (for ex: to cancel the unzip // operation, etc) use method is.close(boolean skipCRCCheck) and set the // flag, skipCRCCheck to false // NOTE: It is recommended to close outputStream first because Zip4j // throws an exception if CRC check fails if (is != null) { // is.close(); boolean skipCRCCheck = false; is.close(skipCRCCheck); is = null; } } }
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Source: https://habr.com/ru/post/954478/

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