Easiest way to convert a Blob into a byte array

Question

what is the easiest way to convert a Blob into a byte array?I am using MYSQL and i want to convert a Blob datatype into a byte array.

Iam using java programming language:)

Timothy Groote · Accepted Answer · 2011-07-12T10:41:03.647

89

the mySql blob class has the following function :

blob.getBytes

use it like this:

//(assuming you have a ResultSet named RS)
Blob blob = rs.getBlob("SomeDatabaseField");

int blobLength = (int) blob.length();  
byte[] blobAsBytes = blob.getBytes(1, blobLength);

//release the blob and free up memory. (since JDBC 4.0)
blob.free();

edited Jul 12 '11 at 10:41

answered Jul 12 '11 at 10:12

Timothy Groote

8,614
26
52

Thanks,actually blob is not having getbytes() method,only serialblob is having getbytes() method.How to do it for blob. – androidGuy Jul 12 '11 at 10:34
2

are you using `java.sql.Blob`? – Timothy Groote Jul 12 '11 at 10:39
this method gives a Lob is closed exception... what do I do ? – Anu Shibin Joseph Raj Jul 18 '17 at 13:22
@AnuShibinJosephRaj i think you should post a full question on SO with an example of your code attached. – Timothy Groote Jul 18 '17 at 13:32
is it a good way to just convert a blob in binary and send via httpclient post request? – Khan Mar 20 '18 at 14:48
@Khan that depends entirely on your situation. what i *can* tell you in advance is that it won't be very fast.. – Timothy Groote Mar 22 '18 at 09:19

Lukas Eder · Answer 2 · 2021-09-19T14:51:30.113

60

The easiest way is this.

byte[] bytes = resultSet.getBytes("my_field");

edited Sep 19 '21 at 14:51

answered Jul 12 '11 at 10:42

Lukas Eder

211,314
129
689
1,509

Excuse me, but I really I have not understood what `rs` is. – Marco Sulla Sep 19 '21 at 14:23
@MarcoSulla: A JDBC `ResultSet` – Lukas Eder Sep 19 '21 at 14:51
I believe this answer is valid only when the field is less than 1048576 bytes. – AJ.P Jan 31 '22 at 00:03
1

@AJ.P: This depends on the SQL dialect. In many dialects, there is no such restriction. – Lukas Eder Jan 31 '22 at 13:05

score 0 · Answer 3 · answered Oct 20 '22 at 12:41

0

You can also get bytes array from Blob instance by this way:

Blob myBlob = null;
byte[] bytes = myBlob.getBinaryStream().readAllBytes();

answered Oct 20 '22 at 12:41

Muhammed_G

375
3
7

Easiest way to convert a Blob into a byte array

3 Answers3

Linked