GZIPInputStream throws unknown format (magic number 213c)

Question

While I used GZIPInputStream to compress bytes get from Internet, the program run error as follows:

05-08 17:37:02.465: W/System.err(744): java.io.IOException: unknown format (magic number 213c)
05-08 17:37:02.465: W/System.err(744):  at java.util.zip.GZIPInputStream.<init>(GZIPInputStream.java:84)
05-08 17:37:02.465: W/System.err(744):  at java.util.zip.GZIPInputStream.<init>(GZIPInputStream.java:64)
05-08 17:37:02.475: W/System.err(744):  at com.Android.Sample.TestActivity.onCreate(TestActivity.java:54)
05-08 17:37:02.475: W/System.err(744):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-08 17:37:02.475: W/System.err(744):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
05-08 17:37:02.475: W/System.err(744):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
05-08 17:37:02.475: W/System.err(744):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
05-08 17:37:02.475: W/System.err(744):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
05-08 17:37:02.475: W/System.err(744):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-08 17:37:02.475: W/System.err(744):  at android.os.Looper.loop(Looper.java:123)
05-08 17:37:02.475: W/System.err(744):  at android.app.ActivityThread.main(ActivityThread.java:3683)
05-08 17:37:02.475: W/System.err(744):  at java.lang.reflect.Method.invokeNative(Native Method)
05-08 17:37:02.475: W/System.err(744):  at java.lang.reflect.Method.invoke(Method.java:507)
05-08 17:37:02.475: W/System.err(744):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-08 17:37:02.475: W/System.err(744):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-08 17:37:02.486: W/System.err(744):  at dalvik.system.NativeStart.main(Native Method)

And My codes as follows:

HttpGet request = new HttpGet("http://www.google.com");
HttpResponse response = new DefaultHttpClient().execute(request);
HttpEntity entity = response.getEntity();
InputStream stream = entity.getContent();
InputStream zippedStream = new GZIPInputStream(stream);
InputStreamReader reader = new InputStreamReader(zippedStream);
BufferedReader buffer = new BufferedReader(reader);

If I just use

InputStreamReader reader = new InputStreamReader(stream);

don't compress the stream,it will be OK.

Answer 1

You must check for Content-Encoding before receive input stream. If the response is encoded in GZIP, use GZIPInputStream. This is my solution, which I use in my API call.

InputStream responseStream = null;
...
// receive response
String encoding = connection.getHeaderField("Content-Encoding");
boolean gzipped = encoding!=null && encoding.toLowerCase().contains("gzip");
try
{
    InputStream inputStream = connection.getInputStream();
    if(gzipped) responseStream = new BufferedInputStream(new GZIPInputStream(inputStream));
    else responseStream = new BufferedInputStream(inputStream);
}
catch(FileNotFoundException e)
{
    // error stream
    InputStream errorStream = connection.getErrorStream();
    if(gzipped) responseStream = new BufferedInputStream(new GZIPInputStream(errorStream));
    else responseStream = new BufferedInputStream(errorStream);
}
...
// TODO: close stream