The example shows how to compress and uncompress 7z files using Java
- 2020-04-01 04:20:54
- OfStack
Compress to 7z file
First of all, there is very little compressed content for 7z on the network.
In particular, Java calls compress less.
The following is a compression done by itself.
I conducted the test and it was successful.
To write a compressed stream as to disk in a compressed file.
Then use 7z compression software to open the decompression.
7 - the open source project 7 zip zip - JBinding (link: http://sourceforge.net/projects/sevenzipjbind/)
Without further ado, the method of calling 7z source code to be compressed is as follows.
public byte[] lzmaZip(String xml) throws IOException{
BufferedInputStream inStream = new BufferedInputStream(new ByteArrayInputStream(xml.getBytes()));
ByteArrayOutputStream bos = new ByteArrayOutputStream();
boolean eos = true;
Encoder encoder = new Encoder();
encoder.SetEndMarkerMode(eos);
encoder.WriteCoderProperties(bos);
long fileSize = xml.length();
if (eos)
fileSize = -1;
for (int i = 0; i < 8; i++)
bos.write((int)(fileSize >>> (8 * i)) & 0xFF);
encoder.Code(inStream, bos, -1, -1, null);
return bos.toByteArray() ;
}
Unzip the 7z file
Use the 7-zip open source project 7-zip-jbinding to unzip a variety of compressed files instead of calling external commands (such as the win call to winrar).
Java's native decompression module has a limited number of decompression types.
Code sample
package core;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Arrays;
import net.sf.sevenzipjbinding.ExtractOperationResult;
import net.sf.sevenzipjbinding.ISequentialOutStream;
import net.sf.sevenzipjbinding.ISevenZipInArchive;
import net.sf.sevenzipjbinding.SevenZip;
import net.sf.sevenzipjbinding.SevenZipException;
import net.sf.sevenzipjbinding.impl.RandomAccessFileInStream;
import net.sf.sevenzipjbinding.simple.ISimpleInArchive;
import net.sf.sevenzipjbinding.simple.ISimpleInArchiveItem;
public class UnZip {
void extractile(String filepath){
RandomAccessFile randomAccessFile = null;
ISevenZipInArchive inArchive = null;
try {
randomAccessFile = new RandomAccessFile(filepath, "r");
inArchive = SevenZip.openInArchive(null, // autodetect archive type
new RandomAccessFileInStream(randomAccessFile));
// Getting simple interface of the archive inArchive
ISimpleInArchive simpleInArchive = inArchive.getSimpleInterface();
System.out.println(" Hash | Size | Filename");
System.out.println("----------+------------+---------");
for (final ISimpleInArchiveItem item : simpleInArchive.getArchiveItems()) {
final int[] hash = new int[] { 0 };
if (!item.isFolder()) {
ExtractOperationResult result;
final long[] sizeArray = new long[1];
result = item.extractSlow(new ISequentialOutStream() {
public int write(byte[] data) throws SevenZipException {
//Write to file
FileOutputStream fos;
try {
File file = new File(item.getPath());
//error occours below
// file.getParentFile().mkdirs();
fos = new FileOutputStream(file);
fos.write(data);
fos.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
hash[0] ^= Arrays.hashCode(data); // Consume data
sizeArray[0] += data.length;
return data.length; // Return amount of consumed data
}
});
if (result == ExtractOperationResult.OK) {
System.out.println(String.format("%9X | %10s | %s", //
hash[0], sizeArray[0], item.getPath()));
} else {
System.err.println("Error extracting item: " + result);
}
}
}
} catch (Exception e) {
System.err.println("Error occurs: " + e);
e.printStackTrace();
System.exit(1);
} finally {
if (inArchive != null) {
try {
inArchive.close();
} catch (SevenZipException e) {
System.err.println("Error closing archive: " + e);
}
}
if (randomAccessFile != null) {
try {
randomAccessFile.close();
} catch (IOException e) {
System.err.println("Error closing file: " + e);
}
}
}
}
}
When invoked:
unzip=new UnZip();
unzip.extractile("a.7z");
Will automatically unzip the files in the zip package to the current directory, of course, you can change the Settings to a specific directory. The code is simple and unambiguous. You can go to the discuss search at the sourceforge project address above for questions.