Extract a .tar.gz file in java (JSP)

问题:

I can't seem to import the packages needed or find any online examples of how to extract a .tar.gz file in java.

What makes it worse is I'm using JSP pages and am having trouble importing packages into my project. I'm copying the .jar's into WebContent/WEB-INF/lib/ and then right clicking on the project and selecting import external jar and importing it. Sometimes the packages resolve, other times they don't. Can't seem to get GZIP to import either. The imports in eclipse for jsp aren't intuitive like they are in normal Java code where you can right click a recognized package and select import.

I've tried the Apache commons library, the ice and another one called JTar. Ice has imported, but I can't find any examples of how to use it?

I guess I need to uncompress the gzipped part first, then open it with the tarstream?

Any help is greatly appreciated.

回答1:

The accepted answer works fine, but I think it is redundant to have a write to file operation.

You could use something like

 TarArchiveInputStream tarInput = 
      new TarArchiveInputStream(new GZipInputStream(new FileInputStream("Your file name")));

 TarArchiveEntry currentEntry = tarInput.getNextTarEntry();
 while(currentEntry != null) {
      File f = currentEntry.getFile();
      // TODO write to file as usual
 }

Hope this help.

Maven Repo

回答2:

Ok, i finally figured this out, here is my code in case this helps anyone in the future. Its written in Java, using the apache commons io and compress librarys.

File dir = new File("directory/of/.tar.gz/files/here");
File listDir[] = dir.listFiles();
if (listDir.length!=0){
    for (File i:listDir){
        /*  Warning! this will try and extract all files in the directory
            if other files exist, a for loop needs to go here to check that
            the file (i) is an archive file before proceeding */
        if (i.isDirectory()){
            break;
        }
        String fileName = i.toString();
        String tarFileName = fileName +".tar";
        FileInputStream instream= new FileInputStream(fileName);
        GZIPInputStream ginstream =new GZIPInputStream(instream);
        FileOutputStream outstream = new FileOutputStream(tarFileName);
        byte[] buf = new byte[1024]; 
        int len;
        while ((len = ginstream.read(buf)) > 0) 
        {
            outstream.write(buf, 0, len);
        }
        ginstream.close();
        outstream.close();
        //There should now be tar files in the directory
        //extract specific files from tar
        TarArchiveInputStream myTarFile=new TarArchiveInputStream(new FileInputStream(tarFileName));
        TarArchiveEntry entry = null;
        int offset;
        FileOutputStream outputFile=null;
        //read every single entry in TAR file
        while ((entry = myTarFile.getNextTarEntry()) != null) {
            //the following two lines remove the .tar.gz extension for the folder name
            String fileName = i.getName().substring(0, i.getName().lastIndexOf('.'));
            fileName = fileName.substring(0, fileName.lastIndexOf('.'));
            File outputDir =  new File(i.getParent() + "/" + fileName + "/" + entry.getName());
            if(! outputDir.getParentFile().exists()){ 
                outputDir.getParentFile().mkdirs();
            }
            //if the entry in the tar is a directory, it needs to be created, only files can be extracted
            if(entry.isDirectory){
                outputDir.mkdirs();
            }else{
                byte[] content = new byte[(int) entry.getSize()];
                offset=0;
                myTarFile.read(content, offset, content.length - offset);
                outputFile=new FileOutputStream(outputDir);
                IOUtils.write(content,outputFile);  
                outputFile.close();
            }
        }
        //close and delete the tar files, leaving the original .tar.gz and the extracted folders
        myTarFile.close();
        File tarFile =  new File(tarFileName);
        tarFile.delete();
    }
}