Read zip archive java

2 Examples to read Zip Files in Java, ZipFile vs ZipInputStream — Tutorial

ZIP format is one of the most popular compression mechanisms in the computer world. A Zip file may contain multiple files or folders in compressed format. Java API provides extensive support to read Zip files, all classes related to zip file processing are located in the java.util.zip package. One of the most common tasks related to zip archive is to read a Zip file and display what entries it contains, and then extract them in a folder. In this tutorial, we will learn how to do this task in Java. There are two ways you can iterate over all items in a given zip archive, you can use either java.util.zip.ZipFile or java.util.zip.ZipInputStream . Since a Zip file contains several items, each of them has a header field containing the size of items in a number of bytes. This means you can iterate all entries without actually decompressing the zip file.

The ZipFile class accepts a java.io.File or String file name, it opens a ZIP file for reading, and the UTF-8 charset is used to decode the entry names and comments.

The main benefit of using ZipFile over ZipInputStream is that it uses random access to iterate over different entries, while ZipInputStream is sequential, because it works with the stream, due to which it’s not able to move positions freely.

It has to read and decompress all zip data in order to reach EOF for each entry and read the header of the next entry. That’s why it’s better to use ZipFile class over ZipInputStream for iterating over all entries from the archive.

We will learn more about how to use read Zip files in Java, by following an example. By the way, code should work with zip file created by any zip utility e.g. WinZip , WinRAR, or any other tool, .ZIP format permits multiple compression algorithms. I have tested with Winzip in Windows 8, but it should work with zip files created by any tool.

How to Read a Zip archive in Java? Example

In this example, I have used ZipFile class to iterate over each file from a Zip archive. getEntry() method of ZipFile returns an entry, which has all metadata including name, size, and modified date and time.

You can ask ZipFile f or InputStream corresponding to this file entry for extracting real data. This means, you only incur the cost of decompression when you really need to. By using java.util.zip.ZipFile , you can check each entry and only extract certain entries, depending upon your logic.

ZipFile is good for both sequential and random access of individual file entries. On the other hand, if you are using ZipInptStream then like any other InputStream, you will need to process all entries sequentially, as shown in the second example.

The key point to remember, especially if you are processing large zip archives is that Java 6 only support zip file up to 2GB. Thankfully Java 7 supports zip64 mode, which can be used to process large zip files with a size of more than 2GB.

Java Program to read Zip File in Java

Here is a complete Java Program to read zip files in Java, you can copy and paste this code to your IDE like Eclipse and IntelliJIDEA to run this code.

import java.io.BufferedInputStream; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.util.Date; import java.util.Enumeration; import java.util.zip.ZipEntry; import java.util.zip.ZipFile; import java.util.zip.ZipInputStream; /** * Java program to iterate and read file entries from Zip archive. * This program demonstrate two ways to retrieve files from Zip * using ZipFile and by using ZipInputStream class. * @author Javin */ public class ZipFileReader < // This Zip file contains 11 PNG images private static final String FILE_NAME = "C:\\temp\\pics.zip"; private static final String OUTPUT_DIR = "C:\\temp\\Images\\"; private static final int BUFFER_SIZE = 8192; public static void main(String args[]) throws IOException < // Prefer ZipFile over ZipInputStream readUsingZipFile(); // readUsingZipInputStream(); > /* * Example of reading Zip archive using ZipFile class */ private static void readUsingZipFile() throws IOException < final ZipFile file = new ZipFile(FILE_NAME); System.out.println("Iterating over zip file : " + FILE_NAME); try < final Enumeration? extends ZipEntry> entries = file.entries(); while (entries.hasMoreElements()) < final ZipEntry entry = entries.nextElement(); System.out.printf("File: %s Size %d Modified on %TD %n", entry.getName(), entry.getSize(), new Date(entry.getTime())); extractEntry(entry, file.getInputStream(entry)); > System.out.printf("Zip file %s extracted successfully in %s", FILE_NAME, OUTPUT_DIR); > finally < file.close(); > > /* * Example of reading Zip file using ZipInputStream in Java. */ private static void readUsingZipInputStream() throws IOException < BufferedInputStream bis = new BufferedInputStream(new FileInputStream(FILE_NAME)); final ZipInputStream is = new ZipInputStream(bis); try < ZipEntry entry; while ((entry = is.getNextEntry()) != null) < System.out.printf("File: %s Size %d Modified on %TD %n", entry.getName(), entry.getSize(), new Date(entry.getTime())); extractEntry(entry, is); > > finally < is.close(); > > /* * Utility method to read data from InputStream */ private static void extractEntry(final ZipEntry entry, InputStream is) throws IOException < String exractedFile = OUTPUT_DIR + entry.getName(); FileOutputStream fos = null; try < fos = new FileOutputStream(exractedFile); final byte[] buf = new byte[BUFFER_SIZE]; int read = 0; int length; while ((length = is.read(buf, 0, buf.length)) >= 0) < fos.write(buf, 0, length); > > catch (IOException ioex) < fos.close(); > > > Output: Iterating over zip file : C:\temp\pics.zip File: Image (11).png Size 21294 Modified on 10/24/13 File: Image (1).png Size 22296 Modified on 11/19/13 File: Image (2).png Size 10458 Modified on 10/24/13 File: Image (3).png Size 18425 Modified on 11/19/13 File: Image (4).png Size 31888 Modified on 11/19/13 File: Image (5).png Size 27454 Modified on 11/19/13 File: Image (6).png Size 67608 Modified on 11/19/13 File: Image (7).png Size 8659 Modified on 11/19/13 File: Image (8).png Size 40015 Modified on 11/19/13 File: Image (9).png Size 17062 Modified on 10/24/13 File: Image (10).png Size 42467 Modified on 10/24/13 Zip file C:\temp\pics.zip extracted successfully in C:\temp\Images\

In order to run this file, make you must have, a zip file with the name pics.zip in C:\temp , and output directory C:\temp\Images available, otherwise it will throw java.lang.NullPointerException. After the successful run of this program, you can see the contents of the zip file extracted inside the output directory.

By the way, as an exercise, you can enhance this program to get the name of the zip file from the user and create an output directory of the same name.

That’s all about How to read Zip files in Java. We have seen two different approaches to iterate over each file entry in Zip file and retrieve them. You should prefer using ZipFile over ZipInputStream for iterating over each file from the archive.

It’s also good to know that java.uti.zip package also supports GZIP file formats, which means you can also read .gz files generated by gzip command in UNIX from your Java program.

Источник

Class ZipInputStream

This class implements an input stream filter for reading files in the ZIP file format. Includes support for both compressed and uncompressed entries.

Field Summary

Fields declared in class java.util.zip.InflaterInputStream

Fields declared in class java.io.FilterInputStream

Constructor Summary

Method Summary

Methods declared in class java.util.zip.InflaterInputStream

Methods declared in class java.io.FilterInputStream

Methods declared in class java.io.InputStream

Methods declared in class java.lang.Object

Field Details

LOCSIG

EXTSIG

CENSIG

ENDSIG

LOCHDR

EXTHDR

CENHDR

ENDHDR

LOCVER

LOCFLG

LOCHOW

LOCTIM

LOCCRC

LOCSIZ

LOCLEN

LOCNAM

LOCEXT

EXTCRC

EXTSIZ

EXTLEN

CENVEM

CENVER

CENFLG

CENHOW

CENTIM

CENCRC

CENSIZ

CENLEN

CENNAM

CENEXT

CENCOM

CENDSK

CENATT

CENATX

CENOFF

ENDSUB

ENDTOT

ENDSIZ

ENDOFF

ENDCOM

Constructor Details

ZipInputStream

ZipInputStream

Method Details

getNextEntry

closeEntry

available

Returns 0 after EOF has reached for the current entry data, otherwise always return 1. Programs should not count on this method to return the actual number of bytes that could be read without blocking.

read

Reads from the current ZIP entry into an array of bytes. If len is not zero, the method blocks until some input is available; otherwise, no bytes are read and 0 is returned.

skip

close

createZipEntry

Report a bug or suggest an enhancement
For further API reference and developer documentation see the Java SE Documentation, which contains more detailed, developer-targeted descriptions with conceptual overviews, definitions of terms, workarounds, and working code examples. Other versions.
Java is a trademark or registered trademark of Oracle and/or its affiliates in the US and other countries.
Copyright © 1993, 2023, Oracle and/or its affiliates, 500 Oracle Parkway, Redwood Shores, CA 94065 USA.
All rights reserved. Use is subject to license terms and the documentation redistribution policy.

Источник

Read zip archive java

Кроме общего функционала для работы с файлами Java предоставляет функциональность для работы с таким видом файлов как zip-архивы. Для этого в пакете java.util.zip определены два класса — ZipInputStream и ZipOutputStream

ZipOutputStream. Запись архивов

Для создания архива используется класс ZipOutputStream. Для создания объекта ZipOutputStream в его конструктор передается поток вывода:

ZipOutputStream(OutputStream out)

Для записи файлов в архив для каждого файла создается объект ZipEntry , в конструктор которого передается имя архивируемого файла. А чтобы добавить каждый объект ZipEntry в архив, применяется метод putNextEntry() .

import java.io.*; import java.util.zip.*; public class Program < public static void main(String[] args) < String filename = "notes.txt"; try(ZipOutputStream zout = new ZipOutputStream(new FileOutputStream("output.zip")); FileInputStream fis= new FileInputStream(filename);) < ZipEntry entry1=new ZipEntry("notes.txt"); zout.putNextEntry(entry1); // считываем содержимое файла в массив byte byte[] buffer = new byte[fis.available()]; fis.read(buffer); // добавляем содержимое к архиву zout.write(buffer); // закрываем текущую запись для новой записи zout.closeEntry(); >catch(Exception ex) < System.out.println(ex.getMessage()); >> >

После добавления объекта ZipEntry в поток нам также надо добавить в него и содержимое файла. Для этого используется метод write, записывающий в поток массив байтов: zout.write(buffer); . В конце надо закрыть ZipEntry с помощью метода closeEntry() . После этого можно добавлять в архив новые файлы — в этом случае все вышеописанные действия для каждого нового файла повторяются.

Чтение архивов. ZipInputStream

Для чтения архивов применяется класс ZipInputStream . В конструкторе он принимает поток, указывающий на zip-архив:

ZipInputStream(InputStream in)

Для считывания файлов из архива ZipInputStream использует метод getNextEntry() , который возвращает объект ZipEntry . Объект ZipEntry представляет отдельную запись в zip-архиве. Например, считаем какой-нибудь архив:

import java.io.*; import java.util.zip.*; public class Program < public static void main(String[] args) < try(ZipInputStream zin = new ZipInputStream(new FileInputStream("output.zip"))) < ZipEntry entry; String name; while((entry=zin.getNextEntry())!=null)< name = entry.getName(); // получим название файла System.out.printf("File name: %s \n", name); // распаковка FileOutputStream fout = new FileOutputStream("new" + name); for (int c = zin.read(); c != -1; c = zin.read()) < fout.write(c); >fout.flush(); zin.closeEntry(); fout.close(); > > catch(Exception ex) < System.out.println(ex.getMessage()); >> >

ZipInputStream в конструкторе получает ссылку на поток ввода. И затем в цикле выводятся все файлы и их размер в байтах, которые находятся в данном архиве.

Затем данные извлекаются из архива и сохраняются в новые файлы, которые находятся в той же папке и которые начинаются с «new».

Источник