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javagzip

Decompress GZip string in Java

I can find plenty of functions that let you decompress a GZip file, but how do I decompress a GZip string?

I'm trying to parse a HTTP response where the response body is compressed with GZip. However, the entire response is simply stored in a string so part of the string contains binary chars.

I'm attempting to use:

byte responseBodyBytes[] = responseBody.getBytes();
ByteArrayInputStream bais = new ByteArrayInputStream(responseBodyBytes); 
GZIPInputStream gzis = new GZIPInputStream(bais);

But that just throws an exception: java.io.IOException: Not in GZIP format

Solution

  • There's no such thing as a GZip string. GZip is binary, strings are text.

    If you want to compress a string, you need to convert it into binary first - e.g. with OutputStreamWriter chained to a compressing OutputStream (e.g. a GZIPOutputStream)

    Likewise to read the data, you can use an InputStreamReader chained to a decompressing InputStream (e.g. a GZIPInputStream).

    One way of easily reading from a Reader is to use CharStreams.toString(Readable) from Guava, or a similar library.