Extraneous data when reading/writing binary data

Question

I am trying to write a process that will retrieve a file (various types - pdf, txt, docx, tif, etc.) via a rest API call, convert that file's binary data from base64 encoding to un-encoded, and write the file to another location (to be picked up by another process). All of the above is working, but if the file type is anything other than txt, the newly written out file will not open.

public File retrieveDocument(String in_ItemId, File in_DestinationFile, Map<String, String> in_DocumentProperties)
        throws IOException {
    byte[] binaryData = new byte[8198];

    try {
        String url = "filestore url";

        RestTemplate restTemplate = new RestTemplate();
        List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();
        messageConverters.add(new MappingJacksonHttpMessageConverter());
        restTemplate.getMessageConverters().add(new StringHttpMessageConverter());
        restTemplate.setMessageConverters(messageConverters);

        Map documentMap = restTemplate.getForObject(url, Map.class);

        if (documentMap.get("binaryData") != null) {
            binaryData = Base64.decodeBase64(((String) documentMap.get("binaryData")).getBytes());
        }

        OutputStream outputStream = new BufferedOutputStream(new FileOutputStream(in_DestinationFile));
        outputStream.write(binaryData);
        outputStream.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

    return in_DestinationFile;
}

When I open both the original and new files in a text editor (i.e., Notepad++) and compare the two, there are a number of additional characters (mainly question marks) in the new file. Below is an example from a tif image. I've added ^ under some of the additional characters in the new file.

Original file:

    II* P  €?à@$
    „BaP¸d6ˆDbQ8¤V-ŒFcQ¸äv=HdR9$–M'”JeR¹d¶]/˜LfS9¤Öm7œNgS¹äö}? PhT:%3Ñ©Tºe6O¨

    ‡ÄbqX¼f7•ß²<¦W-—ÌfsY¼æw=ŸÐhlÐ=—M§ÔjuZ½f·]¯Øll™-–×m·Ünw[½æ÷}¿à_tœ'Çäry\¾g7hÚsú]

New file:

    II* P  €?à@$
    „BaP¸d6ˆDbQ8¤V-ŒFcQ¸äv=?HdR9$–M'”JeR¹d¶]/˜LfS9¤Öm7œNgS¹äö}? PhT:%3Ñ©Tºe6?O¨
                           ^                                                ^
    ‡ÄbqX¼f7?•ß²<¦W-—ÌfsY¼æw=ŸÐhlÐ=—M§ÔjuZ½f·]¯Øll™-–×m·Ünw[½æ÷}¿à_tœ'?Çäry\¾g7?hÚsú]
            ^                                                                  ^

Any ideas as to what I'm doing wrong?

String is a sequence of char[], not byte[]. It is not appropriate to represent binary data. — Andy Turner
– Andy Turner, Commented Apr 7, 2016 at 16:31

Kayaman · Accepted Answer · 2016-04-07 16:13:11Z

2

Writer classes including PrintWriter are for text data. Stream classes such as OutputStream are for binary data.

You're converting binary data into a String at which point some binary data can get corrupted.

Get rid of the String strBinaryData and just the byte[] you get from Base64.decodeBase64.

answered Apr 7, 2016 at 16:13

Kayaman

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5 Comments

F Brooks Over a year ago

I'm missing something here. If I change strBinaryData = new String(Base64.decodeBase64(((String) documentMap.get("binaryData")).getBytes())); to byte[] binaryData = Base64.decodeBase64(((String) documentMap.get("binaryData")).getBytes());, the file doesn't get created at all.

Kayaman Over a year ago

Well if you did that change, there's a lot of other changes your code needs since there's no more strBinaryData. Edit your post to show the current version.

F Brooks Over a year ago

I had made other changes to support the new byte[], but hadn't listed them in my last comment. When those didn't work, I had done some more digging and tried some other things in conjunction with the above suggestion. When I tried to revert things to just the suggested changes, I managed to stumble into a working process. I have edited my original post to show what I have now, which appears to be working. Thanks.

Kayaman Over a year ago

Looks good, except you'll want to put a BufferedOutputStream before the naked FileOutputStream, since without it there's usually a noticeable performance hit.

F Brooks Over a year ago

I've added that as well. Thanks.

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