Develop Reference

How to decompress BZIP (not BZIP2) with Apache Commons

I have been working on a task to decompress from different types of file format such as "zip,tar,tbz,tgz". I am able to do for all except tbz because apache common compress library provides BZIP2 compressors. But I need to decompress a old BZIP not BZIP2. Is there any way to do it java. I have added the code I have done so far for extracting different tar file archives using apache commons library below.
public List<ArchiveFile> processTarFiles(String compressedFilePath, String fileType) throws IOException {
List<ArchiveFile> extractedFileList = null;
TarArchiveInputStream is = null;
FileOutputStream fos = null;
BufferedOutputStream dest = null;
try {
if(fileType.equalsIgnoreCase("tar"))
{
is = new TarArchiveInputStream(new FileInputStream(new File(compressedFilePath)));
}
else if(fileType.equalsIgnoreCase("tbz")||fileType.equalsIgnoreCase("bz"))
{
is = new TarArchiveInputStream(new BZip2CompressorInputStream(new FileInputStream(new File(compressedFilePath))));
}
else if(fileType.equalsIgnoreCase("tgz")||fileType.equalsIgnoreCase("gz"))
{
is = new TarArchiveInputStream(new GzipCompressorInputStream(new FileInputStream(new File(compressedFilePath))));
}
TarArchiveEntry entry = is.getNextTarEntry();
extractedFileList = new ArrayList<>();
while (entry != null) {
// grab a zip file entry
String currentEntry = entry.getName();
if (!entry.isDirectory()) {
File destFile = new File(Constants.DEFAULT_ZIPOUTPUTPATH, currentEntry);
File destinationParent = destFile.getParentFile();
// create the parent directory structure if needed
destinationParent.mkdirs();
ArchiveFile archiveFile = new ArchiveFile();
int currentByte;
// establish buffer for writing file
byte data[] = new byte[(int) entry.getSize()];
// write the current file to disk
fos = new FileOutputStream(destFile);
dest = new BufferedOutputStream(fos, (int) entry.getSize());
// read and write until last byte is encountered
while ((currentByte = is.read(data, 0, (int) entry.getSize())) != -1) {
dest.write(data, 0, currentByte);
}
dest.flush();
dest.close();
archiveFile.setExtractedFilePath(destFile.getAbsolutePath());
archiveFile.setFormat(destFile.getName().split("\\.")[1]);
extractedFileList.add(archiveFile);
entry = is.getNextTarEntry();
} else {
new File(Constants.DEFAULT_ZIPOUTPUTPATH, currentEntry).mkdirs();
entry = is.getNextTarEntry();
}
}
} catch (IOException e) {
System.out.println(("ERROR: " + e.getMessage()));
} catch (Exception e) {
System.out.println(("ERROR: " + e.getMessage()));
} finally {
is.close();
dest.flush();
dest.close();
}
return extractedFileList;
}

The original Bzip was supposedly using a patented algorithm so Bzip2 was born using algorithms and techniques that were not patented.
That might be the reason why it's no longer in widespread use and open source libraries ignore it.
There's some C code for decompressing Bzip files shown here (gist.github.com mirror).
You might want to read and rewrite that in Java.

Downloading multiple files in java

Here in my list i am having multiple files but while downloading only the first file in my list is getting downloaded.
for(FileAttachemntActionVo fileAttachemntActionVoItr : fileAttachemntActionVoList){
ServletOutputStream out = servletResponse.getOutputStream();
servletResponse.setContentType("multipart/x-mixed-replace;boundary=END");
servletResponse.setHeader("Content-Disposition","attachment; filename="+fileAttachemntActionVoItr.getAttachmentFileName());
//}
FileInputStream fileInputStream = null;
try{
fileInputStream = new FileInputStream(fileAttachemntActionVoItr.getAttachmentUrl() + fileAttachemntActionVoItr.getAttachmentFileName());
}catch(FileNotFoundException fnfe){
fnfe.getStackTrace();
}
BufferedInputStream fif = new BufferedInputStream(fileInputStream);
int i = 0;
while ((i = fif.read()) != -1) {
out.write(i);
}
fif.close();
out.close();
}

Do not close the output stream, take a look at this post. Let the container handle the stream.

How to read a binary file, modify the same file and save the file with the modifications?

I am currently working a project and we have divided it in modules, in one of them, we have a file ( .exe ) extension. I decided to open it in binary format and read the contents of it, modify them. But, I am not to modify the changes and save it in the same file. When I am trying to do so, it says 0KB. It's working perfectly fine when using two files.
Here is the source code :
public static void main(String[] args) {
String strSourceFile="E:/e.exe";
String strDestinationFile="E:/f.exe";
try
{
FileInputStream fin = new FileInputStream(strSourceFile);
FileOutputStream fout = new FileOutputStream(strDestinationFile);
byte[] b = new byte[1];
int noOfBytes = 0;
System.out.println("Copying file using streams");
while( (noOfBytes = fin.read(b)) != -1 )
{
fout.write(b, 0, noOfBytes);
}
System.out.println("File copied!");
//close the streams
fin.close();
fout.close();

Use RandomAccessFile or You can also create a new file with your changes save it and delete the original one. Once original file is deleted then rename this new file to the original one.

You are trying to read and write the same file with the input and the output stream so the file is not getting copied while you try to do it with the same file. Instead, use a middle file as the buffer, as in the below code I have used the f.exe as the middle buffer, next I have copied the data from the buffer file again to the original file jar.exe, at last you need to delete the buffer file.
Here is the below code :
String strSourceFile = "C:/jar.exe";
String strDestinationFile = "C:/f.exe";
FileInputStream fin = new FileInputStream(strSourceFile);
FileOutputStream fout = new FileOutputStream(strDestinationFile);
byte[] b = new byte[1];
int noOfBytes = 0;
System.out.println("Copying file using streams");
while ((noOfBytes = fin.read(b)) != -1) {
fout.write(b, 0, noOfBytes);
}
fin.close();
fout.close();
String strDestinationFile1 = "C:/jar.exe";
FileInputStream fin1 = new FileInputStream(strDestinationFile);
FileOutputStream fout1 = new FileOutputStream(strDestinationFile1);
while ((noOfBytes = fin1.read(b)) != -1) {
fout1.write(b, 0, noOfBytes);
}
System.out.println("File copied!");
//close the streams
fin1.close();
fout1.close();
File file = new File("C:/f.exe");
file.delete();

Reading gzip files inside gzip file using Java

Using Java I have to read text files which are inside gz file which is in another .tar.gz
gz_ltm_logs.tar.gz is the filename. It then has files ltm.1.gz, ltm.2.gz inside it and then these files have text files in them.
I wanted to do it using java.util.zip.* only but if it is impossible then I can look at other libraries.
I thought I will be able to do it using java.util.zip. But doesn't seem straightforward

Here's some code to give you an idea. This method will try to extract a given tar.gz file to outputFolder.
public static void extract(File input, File outputFolder) throws IOException {
byte[] buffer = new byte[1024];
GZIPInputStream gzipFile = new GZIPInputStream(new FileInputStream(input));
ByteOutputStream tarStream = new ByteOutputStream();
int gzipLengthRead;
while ((gzipLengthRead = gzipFile.read(buffer)) > 0){
tarStream.write(buffer, 0, gzipLengthRead);
}
gzipFile.close();
org.apache.tools.tar.TarInputStream tarFile = null;
// files inside the tar
OutputStream out = null;
try {
tarFile = new org.apache.tools.tar.TarInputStream(tarStream.newInputStream());
tarStream.close();
TarEntry entry = null;
while ((entry = tarFile.getNextEntry()) != null) {
String outFilename = entry.getName();
if (entry.isDirectory()) {
File directory = new File(outputFolder, outFilename);
directory.mkdirs();
} else {
File outputFile = new File(outputFolder, outFilename);
File outputDirectory = outputFile.getParentFile();
if (!outputDirectory.exists()) {
outputDirectory.mkdirs();
}
out = new FileOutputStream(outputFile);
// Transfer bytes from the tarFile to the output file
int innerLen;
while ((innerLen = tarFile.read(buffer)) > 0) {
out.write(buffer, 0, innerLen);
}
out.close();
}
}
} finally {
if (tarFile != null) {
tarFile.close();
}
if (out != null) {
out.close();
}
}
}

Android FileReader from R.raw.file

Really newbie question:
I have a .csv file that I need to read. I've put it in the raw folder. For convenience, Im' using the http://opencsv.sourceforge.net/ library for reading the file. The library provides this method for creating a CSVReader object:
CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
But I don0't get how to point this constructor to my file, since the file in Android is usually referenced like R.raw.file rather than a String address to the file.
Any help would be greatly appreciated.

You want to do something like this -
public void readCSVFromRawResource(Context context)
{
//this requires there to be a dictionary.csv file in the raw directory
//in this case you can swap in whatever you want
InputStream inputStream = getResources().openRawResource(R.raw.dictionary);
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
try
{
String word;//word
int primaryKey = 0;//primary key
Map dictionaryHash = new HashMap();
while ((word = reader.readLine()) != null)
{
if(word.length() < 7)
{
dictionaryHash.put(primaryKey,word );
primaryKey++;
if(primaryKey % 1000 == 0)
Log.v("Percent load completed ", " " + primaryKey);
}
}
//write the dictionary to a file
File file = new File(DICTIONARY_FILE_NAME);
BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(DICTIONARY_FILE_NAME));
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(dictionaryHash);
oos.flush();
oos.close();
Log.v("alldone","done");
}
catch (Exception ex) {
// handle exception
Log.v(ex.getMessage(), "message");
}
finally
{
try
{
inputStream.close();
}
catch (IOException e) {
// handle exception
Log.v(e.getMessage(), "message");
}
}
}

You can use this solution to get a String from the raw resource:
Android read text raw resource file
then use StringReader instead of FileReader with the CSVReader constructor.