[FIXED] Java: ZIP Files downloaded with HTTPUrlConnection are corrupted

Issue

I am migrating a webapp from Java 8 to 11 (and Tomcat 8 to 9) and i have a Client that downloads ZIP Archive Files from a Service using the following methods:

public HTTPResponse doGet(String aUrl, HashMap<String,String> aRequestParams, HashMap<String,String> aRequestProperties)
throws Exception
{
    try
    {
        String lUrl = aUrl;
        if (aRequestParams != null && aRequestParams.size() > 0)
        {
             StringBuffer lBodyStringBuffer = new StringBuffer();
             for(String lParam : aRequestParams.keySet())
             {
                 String lValue = aRequestParams.get(lParam);
                 if(lValue != null && !"".equals(lValue.trim()))
                 {
                     if(lBodyStringBuffer.length() > 0)
                     {
                         lBodyStringBuffer.append("&");
                     }
                     lBodyStringBuffer.append(URLEncoder.encode(lParam, sDEFAULTENCODING)).append("=").append(URLEncoder.encode(lValue, sDEFAULTENCODING));
                 }
             }
             String lParamString = lBodyStringBuffer.toString();
             if (lParamString != null && lParamString.length() > 0)
             {
                 if (!(lUrl.endsWith(sURLPARAMSLEADER) || aUrl.endsWith(sURLPARAMSSEPARATOR)))
                 {
                     if (lUrl.indexOf(sURLPARAMSLEADER) > -1)
                     {
                         lUrl = lUrl + sURLPARAMSSEPARATOR;
                     }
                     else
                     {
                         lUrl = lUrl + sURLPARAMSLEADER;
                     }
                 }
                 lUrl = lUrl + lParamString;
             }

        }
        HttpURLConnection lConnection = createConnection(lUrl,sREQUESTETHOD_GET,null, aRequestProperties);
        HTTPResponse lReturn = getResponseFromConnection(lConnection);
        return lReturn;
    }
    catch(Exception lException)
    {
        throw new Exception("Fehler beim Durchführen der Anfrage: " + lException.getMessage(), lException);
    }
}

private HTTPResponse getResponseFromConnection(HttpURLConnection aConnection)
throws Exception
{
    InputStream lConnectionInputStream = null;
    ByteArrayOutputStream lResponseByteArrayOutputStream = null;
    try
    {
        aConnection.setRequestProperty("Accept", "application/zip");
        int lStatusCode = aConnection.getResponseCode();
        String lResponseCharset = getCharsetFromResponseContentType(aConnection.getContentType());
        if (lResponseCharset == null)
        {
            if (lResponseCharset == null ||lResponseCharset.trim().length() == 0)
            {
                lResponseCharset = "UTF-8";
            }
        }
        if (HttpURLConnection.HTTP_OK == lStatusCode)
        {
            lConnectionInputStream = aConnection.getInputStream();
        }
        else
        {
            lConnectionInputStream = aConnection.getErrorStream();
        }
        String lMessage = "";
        if (lConnectionInputStream != null)
        {
            lResponseByteArrayOutputStream = new ByteArrayOutputStream();
            int lBufferSize = 4096;
            byte[]  lBuffer = new byte[lBufferSize];
            int lLength = 0;
            while ((lLength = lConnectionInputStream.read(lBuffer, 0, lBufferSize)) != -1)
            {
                lResponseByteArrayOutputStream.write(lBuffer, 0, lLength);
            }
            byte[] lResponseByte =  lResponseByteArrayOutputStream.toByteArray();
            lMessage = new String (lResponseByte,lResponseCharset);
        }
        HTTPResponse lReturn = new HTTPResponse(lStatusCode, lMessage);
        return lReturn;
    }
    catch(Exception lException)
    {
        throw lException;
    }
    finally
    {
        if (lResponseByteArrayOutputStream != null)
        {
            try{lResponseByteArrayOutputStream.close();}catch(Exception e){}
        }
        if (lConnectionInputStream != null)
        {
            try{lConnectionInputStream.close();}catch(Exception e){}
        }
    }
}

This is how i actually call the service via HTTP Get and save the data:

HTTPResponse lResponse = new HTTPRequest().doGet("http://localService.com/, null, null);
FileOutputStream lFileOutputStream = new FileOutputStream("exampleFile.zip", false);
lFileOutputStream.write(lResponse.getMessage().getBytes());
lFileOutputStream.close();

So this used to Work before and i am getting a headache about what might have changed. When i download the ZIP File with url in my Browser, everything seems fine, so the Service seems to work. But with my client the ZIP Files get corrupted and cannot be opened. The are not empty but they differ in size: surprisingly the corrupted files are about 50% larger than the ones downloaded via browser.

Does anyone know what the problem here is?

Solution

Ok,the problem was the return type String of the method getResponseFromConnection. I changed it and now write the file directly with the File.copy() method which VGR suggested.

Answered By - flixe