How to read from GZIPInputstream

Question

Scenario is to read a gzip file(.gz extension)

Got to know that there is GZIPInputStream class to handle this.

Here is the code to convert file object to GZIPStream.

FileInputStream fin = new FileInputStream(FILENAME);
 GZIPInputStream gzis = new GZIPInputStream(fin);

Doubt is how to read content from this 'gzis' object?

I am confused, that is just an InputStream, you read it like any other InputStream. — njzk2, Mar 04 '16 at 06:19
You read the GZIPInputStream in exactly the same way you'd read the FileInputStream if the data had not been GZipped. If binary, you read into byte arrays. If text, you wrap with an InputStreamReader, specifying the character encoding. — Andreas, Mar 04 '16 at 06:24
http://stackoverflow.com/questions/1080381/gzipinputstream-reading-line-by-line — matt, Mar 04 '16 at 06:49

Kordi · Accepted Answer · 2016-03-04T06:35:13.133

22

Decode bytes from an InputStream, you can use an InputStreamReader. A BufferedReader will allow you to read your stream line by line.

If the zip is a TextFile

ByteArrayInputStream bais = new ByteArrayInputStream(responseBytes);
GZIPInputStream gzis = new GZIPInputStream(bais);
InputStreamReader reader = new InputStreamReader(gzis);
BufferedReader in = new BufferedReader(reader);

String readed;
while ((readed = in.readLine()) != null) {
  System.out.println(readed);
}

As noticed in the comments. It will ignore the encoding, and perhaps not work always properly.

Better Solution

It will write the uncompressed data to the destinationPath

FileInputStream fis = new FileInputStream(sourcePath);
FileOutputStream fos = new FileOutputStream(destinationPath);
GZIPInputStream gzis = new GZIPInputStream(fis);
byte[] buffer = new byte[1024];
int len = 0;

while ((len = gzis.read(buffer)) > 0) {
    fos.write(buffer, 0, len);
}

fos.close();
fis.close();
gzis.close();

edited Mar 04 '16 at 06:35

answered Mar 04 '16 at 06:23

Kordi

2,405
1
14
13

2

Assuming the gzipped content is text, and not binary data. – Andreas Mar 04 '16 at 06:24
This assumes the content is text, and composed of lines. And ignores which encoding could have been used – njzk2 Mar 04 '16 at 06:24
The content is text only. What you mean by ingores the encoding? – Aajan Mar 04 '16 at 06:28
If the content is text only then use the first solution. It then just outputs the string. The second solution writes, the unzipped file to destination path. – Kordi Mar 04 '16 at 06:30
@Andreas now satisfied. Thanks for the notice. – Kordi Mar 04 '16 at 06:30
@njzk2 Now satisfied! Thanks for the notice – Kordi Mar 04 '16 at 06:30
@Aajan In the first solution i assume that it'is text. Use the second solution to write it to the destination path. – Kordi Mar 04 '16 at 06:33

score 2 · Answer 2 · answered Mar 04 '16 at 10:21

2

I recommended you to use Apache Commons Compress API

add Maven dependency:

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-compress</artifactId>
    <version>1.10</version>
</dependency>

then use GZipCompressorInputStream class, example described here

answered Mar 04 '16 at 10:21

Eugene Lebedev

1,400
1
18
30

Can u show some example @Eugene Lebedev – Navigator Sep 18 '22 at 04:40
@Navigator https://commons.apache.org/proper/commons-compress/examples.html – Eugene Lebedev Sep 19 '22 at 13:46

How to read from GZIPInputstream

2 Answers2

Linked