Question

I have a problem, which I do not seem to be able to solve… I do a http download of a file, but the CRC32 of the file on the server and on the client do not match. Also, the file has different size, so obviously I must be doing something wrong… when I download via Firefox, the filesize is ok… so I guess it is somewhere in the client code.

I already found Corrupt file when using Java to download file, but that didn’t help me either…

Here’s the code:

private void downloadJar(String fileName, long crc32Server) throws IOException {   System.out.println('Downloading file '' + fileName + '' from server '' + mServer + ''.');   HttpURLConnection sourceConnection = null;   BufferedInputStream inputStream = null;   BufferedWriter fileWriter = null;   long crc32Client;   try {     URL sourceURL = new URL(fileName);     try {       sourceConnection = (HttpURLConnection)sourceURL.openConnection();     }     catch (MalformedURLException exc) {       throw new RuntimeException('Configured URL caused a MalformedURLException: ', exc);     }     sourceConnection.setRequestProperty('Accept-Encoding', 'zip, jar');     sourceConnection.connect();     inputStream = new BufferedInputStream(sourceConnection.getInputStream());     fileWriter = new BufferedWriter(new FileWriter(targetFolder + File.separator + fileName));     CRC32 crc32 = new CRC32();     for (int singleByte = inputStream.read(); singleByte != -1; singleByte = inputStream.read()) {       fileWriter.write(singleByte);       crc32.update(singleByte);     }     crc32Client = crc32.getValue();   }   finally {     if (inputStream != null) {       inputStream.close();     }     if (fileWriter != null) {       fileWriter.flush();       fileWriter.close();     }     if (sourceConnection != null) {       sourceConnection.disconnect();     }   }   if (crc32Client != crc32Server) {     //      deleteFile(fileName);     throw new IOException('CRC32 did not match for file '' + fileName + '': ' + crc32Client + '!='         + crc32Server);   } } 

Answer 1

You should use a BufferedOutputStream instead of a FileWriter/BufferedWriter. In general, *Streams handle raw binary data, while *Writers handle character data (which is an interpretation of the raw binary data for a given character encoding).