Java – Create Password Protected Zip File

This tutorial covers creating password-protected zip files using a very useful library zip4j. Java, by default, does not provide any support for password protection for file; though it has very good API support for creating/extracting zip files. There are some other useful libraries out there, which are equally good and sometimes better than zip4j, but they use some native code as well, which makes their usage platform dependent to some extent. Zip4j uses completely java code without any support of native code, and that’s what makes it a better fit for me.

Zip4j provides following features:

• Create, Add, Extract, Update, Remove files from a Zip file
• Read/Write password protected Zip files
• Supports AES 128/256 Encryption
• Supports Standard Zip Encryption
• Supports Zip64 format
• Supports Store (No Compression) and Deflate compression method
• Create or extract files from Split Zip files (Ex: z01, z02,…zip)
• Supports Unicode file names
• Progress Monitor

1) Download and Include Zip4j library into Project

To download the Zip4j library, go to its zip4j download page and download it’s latest version (zip4j_1.3.2.jar till today).

Add zip4j.jar file into your project’s classpath.

2) Example of creating password protected zip file

Now, you can use the below code to create a password protected archive.

import java.io.File;
import java.util.ArrayList;

import net.lingala.zip4j.core.ZipFile;
import net.lingala.zip4j.exception.ZipException;
import net.lingala.zip4j.model.ZipParameters;
import net.lingala.zip4j.util.Zip4jConstants;

public class CreatePasswordProtectedZipExample
{
	public static void main(String[] args) 
	{
		try {
			//This is name and path of zip file to be created
			ZipFile zipFile = new ZipFile("C:/temp/test.zip");
			
			//Add files to be archived into zip file
			ArrayList<File> filesToAdd = new ArrayList<File>();
			filesToAdd.add(new File("C:/temp/test1.txt"));
			filesToAdd.add(new File("C:/temp/test2.txt"));
			
			//Initiate Zip Parameters which define various properties
			ZipParameters parameters = new ZipParameters();
			parameters.setCompressionMethod(Zip4jConstants.COMP_DEFLATE); // set compression method to deflate compression
			
			//DEFLATE_LEVEL_FASTEST 	- Lowest compression level but higher speed of compression
			//DEFLATE_LEVEL_FAST 		- Low compression level but higher speed of compression
			//DEFLATE_LEVEL_NORMAL 	- Optimal balance between compression level/speed
			//DEFLATE_LEVEL_MAXIMUM 	- High compression level with a compromise of speed
			//DEFLATE_LEVEL_ULTRA 		- Highest compression level but low speed
			parameters.setCompressionLevel(Zip4jConstants.DEFLATE_LEVEL_NORMAL); 
			
			//Set the encryption flag to true
			parameters.setEncryptFiles(true);
			
			//Set the encryption method to AES Zip Encryption
			parameters.setEncryptionMethod(Zip4jConstants.ENC_METHOD_AES);
			
			//AES_STRENGTH_128 - For both encryption and decryption
			//AES_STRENGTH_192 - For decryption only
			//AES_STRENGTH_256 - For both encryption and decryption
			//Key strength 192 cannot be used for encryption. But if a zip file already has a
			//file encrypted with key strength of 192, then Zip4j can decrypt this file
			parameters.setAesKeyStrength(Zip4jConstants.AES_STRENGTH_256);
			
			//Set password
			parameters.setPassword("howtodoinjava");
			
			//Now add files to the zip file
			zipFile.addFiles(filesToAdd, parameters);
		} 
		catch (ZipException e) 
		{
			e.printStackTrace();
		}
	}
}

There are other useful usecases, you can look into it’s source distribution [zip4j_examples_eclipse_1.3.2.zip] as well. Checkout this wonderfully useful library.

Happy Learning !!

Reference : http://www.lingala.net/zip4j/