How to upload a byte array into BLOB column?

[Steven Ho]

I hava a BLOB column inside sample table. On the other hand I manage to get a byte array (byte[]) from files uploaded by form input field.
Is it possible to upload the byte array into the field? I am trying to add a file into database.
I tried to find a way to convert the byte array into BLOB using
byte[] b = .... populate it with byte data
Blob blob = null;
blob.setBytes(1, b);
This doesn't work because the blob object is null.
Please help, thank you all.

[Jon Dornback]

I solved this by using the following code (try{} blocks ommitted):

      String sql = "INSERT INTO testtable(stringcolumn, blobcolumn) VALUES(?,?)";
      String testString = "hello world";
      byte[] testBytes  = "this is a test".getBytes();
      int rowsaffected = 0;
   
      PreparedStatement statement = connection.prepareStatement(sql);

      statement.setString(1,testString);
      statement.setBinaryStream(2,new ByteArrayInputStream(testBytes),testBytes.length);
      rowsaffected = statement.executeUpdate();

The basic idea is that you use a PreparedStatement, which allows you to set a BinaryStream as part of the insert. Then, wrap the byte[] array with a new ByteArrayInputStream, and set that as the binary stream to be inserted.
to get the byte array back out of the database, use this:

// assuming theID is passed in from somewhere
String sql = "SELECT blobcolumn FROM testtable WHERE theID="+theID;
Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
ResultSet result    = statement.executeQuery(sql);
if(result.next()){ // got at least one row, and only one row if theID is primary key
   Blob blob = result.getBlob("blobcolumn"); // creates the blob object from the result
   /*
      blob index starts with 1 instead of 0, and starting index must be (long).
      we want all the bytes back, so this grabs everything.
      keep in mind, if the blob is longer than max int length, this won't work right
      because a byte array has max length of max int length.
   */
   byte[] theBytes = blob.getBytes(1L, (int)blob.length());
   // just to make sure:
   System.out.println("blob back to string |"+new String(theBytes)+"|");
}

[Steven Ho]

Thank you Jon, I have done my work based on your guidance.