Exception in thread "main" java.util.zip.ZipException: Not in GZIP format. when compressing file using ISO charset

Question

I'm trying in my program to Compress/Decompress data using GZIP streams and when using the charset "ISO-8859-1", everything working well but when changing the charset to "UTF-8", i'm getting the Error message "Exception in thread "main" java.util.zip.ZipException: Not in GZIP format". this is my code:

public static String compress(String str) throws IOException { 
       if (str == null || str.length() == 0) { 
           return str; 
       } 
       System.out.println("String length : " + str.length()); 
       ByteArrayOutputStream out = new ByteArrayOutputStream(); 
       GZIPOutputStream gzip = new GZIPOutputStream(out); 
       gzip.write(str.getBytes()); 
       gzip.close(); 
       String outStr = out.toString("UTF-8"); 
       System.out.println("Output String lenght : " + outStr.length()); 
       System.out.println("Output : " + outStr.toString()); 
       return outStr; 
} 

public static String decompress(String str) throws IOException { 
       if (str == null || str.length() == 0) { 
          return str; 
       } 
       System.out.println("Input String length : " + str.length()); 
       GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(str.getBytes("UTF-8"))); 
       BufferedReader bf = new BufferedReader(new InputStreamReader(gis, "UTF-8")); 
       String outStr = ""; 
       String line; 
       while ((line=bf.readLine())!=null) { 
             outStr += line; 
       } 
       System.out.println("Output String lenght : " + outStr.length()); 
       return outStr; 
} 

public static void main(String[] args) throws IOException { 
       String string = "my data"; 
       System.out.println("after compress:"); 
       String compressed = compress(string); 
       System.out.println(compressed); 
       System.out.println("after decompress:"); 
       String decomp = decompress(compressed); 
       System.out.println(decomp); 
} 

Answer 1

String outStr = out.toString("UTF-8"); This "out" is ziped byte stream,encode it to String then decode it from String will be lose some bytes.This maybe a bug of java. To Resolve it,you can encode bytes to String in compress() to return, such as :

String infoBase64Encode = new String(Base64.encodeBase64(out.toByteArray()))

decode String to bytes in decompress() to return, such as :

String infoBase64Decode = Base64.decodeBase64(decryptAESinfo)

complete code as follows:

public static String compress(String str) throws IOException { 
           if (str == null || str.length() == 0) { 
               return str; 
           } 
           System.out.println("String length : " + str.length()); 
           ByteArrayOutputStream out = new ByteArrayOutputStream(); 
           GZIPOutputStream gzip = new GZIPOutputStream(out); 
           gzip.write(str.getBytes()); 
           gzip.close(); 
           String outStr = new String(Base64.encodeBase64(out.toByteArray()));
           System.out.println("Output String lenght : " + outStr.length()); 
           System.out.println("Output : " + outStr.toString()); 
           return outStr; 
    } 

    public static String decompress(String str) throws IOException { 
           if (str == null || str.length() == 0) { 
              return str; 
           } 
           System.out.println("Input String length : " + str.length()); 
           GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(Base64.decodeBase64(str))); 
           String outStr = ""; 
           ByteArrayOutputStream out = new ByteArrayOutputStream();
           byte[] buffer = new byte[256];
           int n;
           while ((n = gis.read(buffer)) >= 0) {
               out.write(buffer, 0, n);
           }
           System.out.println("Output String lenght : " + outStr.length()); 
           return new String(out.toByteArray()); 
    } 

    public static void main(String[] args) throws IOException { 
           String string = "my data"; 
           System.out.println("after compress:"); 
           String compressed = compress(string); 
           System.out.println(compressed); 
           System.out.println("after decompress:"); 
           String decomp = decompress(compressed); 
           System.out.println(decomp); 
    }