Convert blob to string to to create a json object and then change the string back to blob

Question

My requirement is to convert the blob in a database field to string to create a json object. I have achieved that.

Now, I need to convert this string back to blob. I wrote the below code. But, it does not work. In my instance, I have the word document stored as blob. I converted it to string but when I converted the string to blob, the document does not open properly.

Please let me know a way to convert the string back to blob.

DocumentTemplateKey documentTemplateKey = new DocumentTemplateKey();
documentTemplateKey.documentTemplateID = "XX";
DocumentTemplateDtls documentTemplateDtls = DocumentTemplateFactory.newInstance().read(documentTemplateKey);

byte[] blobAsBytes = documentTemplateDtls.contents.copyBytes();

ByteArrayOutputStream bos = new ByteArrayOutputStream();


bos.write(blobAsBytes, 0, blobAsBytes.length);

String pdfBase64String = 
  org.apache.commons.codec.binary.StringUtils.newStringUtf8(org.apache.
  commons.codec.binary.Base64.encodeBase64(bos.toByteArray()));

OutputStreamWriter out = new OutputStreamWriter(System.out);
JsonWriter writer = new JsonWriter(out);
//set indentation for pretty print
writer.setIndent("\t");
//start writing
writer.beginObject(); //{
writer.name("blob").value(pdfBase64String);
byte[] stringAsBytes =  org.apache.commons.codec.binary.StringUtils.getBytesUtf8(pdfBase64String);

Blob blob = new Blob(stringAsBytes);
documentTemplateDtls.contents = blob;
documentTemplateDtls.documentTemplateID = "XX12";
documentTemplateDtls.name = "XX12";
DocumentTemplateFactory.newInstance().insert(documentTemplateDtls);
writer.endObject();

writer.flush();

//close writer
writer.close();

Take a look at stackoverflow.com/a/32425109/5910038, maybe it will help. — Ethan
– Ethan, Commented Nov 8, 2018 at 8:42
The code is full of strange parts, like after that multi-line fight with ByteArrayOutputStream, bos.toByteArray() simply gets you an identical copy of blobAsBytes. Also, instead of the encodeBase64+StringUtils magic, you could just directly use encodeBase64String() providing a String for you directly. Note that Java itself has Base64 too, starting from Java8. — tevemadar
– tevemadar, Commented Nov 8, 2018 at 11:37
(2nd part) After that you write some JSON to the standard output, while starting to write something back to your blob, using pdfBase64String, so not a JSON. — tevemadar
– tevemadar, Commented Nov 8, 2018 at 11:41

Bruce Hamilton · Accepted Answer · 2018-11-08 08:46:06Z

0

Here's your problem:

byte[] stringAsBytes = org.apache.commons.codec.binary.StringUtils.getBytesUtf8(pdfBase64String);

You're getting the bytes of your base64 string, but you ought to be putting it through a base64 decoder.

answered Nov 8, 2018 at 8:46

Bruce Hamilton

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1 Comment

Gurunathan Over a year ago

Thanks. Once I changed it to byte[] stringAsBytes = DatatypeConverter.parseBase64Binary(pdfBase64String); it worked like a charm.

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