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From "Laurenz Albe (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-463) Successive writes to a java.sql.Blob.setBinaryStream(long) seem to reset the file pointer
Date Tue, 16 Aug 2005 14:07:56 GMT
    [ http://issues.apache.org/jira/browse/DERBY-463?page=comments#action_12318896 ] 

Laurenz Albe commented on DERBY-463:
------------------------------------

While you are at it:

In my program there is a line of code:
  java.io.OutputStream outstream = blob.setBinaryStream(1l);

My original attempt was with blob.setBinaryStream(0l), as it should be in my opinion,
but then the first byte written to the Blob does not get written, i.e. the resulting Blob
is one byte
short. By trial and error I found that it works when I use 1 instead of 0.

Is that also a bug or is that intended?

> Successive writes to a java.sql.Blob.setBinaryStream(long) seem to reset the file pointer
> -----------------------------------------------------------------------------------------
>
>          Key: DERBY-463
>          URL: http://issues.apache.org/jira/browse/DERBY-463
>      Project: Derby
>         Type: Bug
>   Components: JDBC
>     Versions: 10.0.2.1
>  Environment: Sun java full version "1.4.2_05-b04"
> Linux x86
> Derby is run in network server mode
>     Reporter: Laurenz Albe
>     Assignee: Fernanda Pizzorno
>  Attachments: DERBY-463.diff, DERBY-463.stat
>
> I have a table
> PEOPLE(SEQ_ID INT NOT NULL PRIMARY KEY, PICTURE BLOB).
> A row is inserted; both values are not NULL.
> From inside a JDBC program, I select the Blob for update.
> I then get the Blob output stream with a call to
>   Blob.setBinaryStream(long)
> To this stream I write several times with
>   OutputStream.write(byte[], int, int)
> I close the stream, update the selected row with the new Blob and commit.
> The new value of the Blob now is exactly the value of the last content of the byte[],
> and it is like the previous calls to write() have never taken place, or as if the file
pointer
> of the output stream has been reset between the calls.
> A sample program follows; the size of the input file "picture.jpg" is 23237, the length
> of the Blob after the program has run is 23237 % 1024 = 709
> ------------ sample program -------------
> import java.sql.*;
> class TestApp {
>    private TestApp() {}
>    public static void main(String[] args)
>          throws ClassNotFoundException, SQLException, java.io.IOException {
>       // try to load JDBC driver
>       Class.forName("com.ibm.db2.jcc.DB2Driver");
>       // open the input file
>       java.io.InputStream instream = new java.io.FileInputStream("picture.jpg");
>       // login to database
>       Connection conn = DriverManager.getConnection(
>             "jdbc:derby:net://dbtuxe/testdb", "laurenz", "apassword");
>       conn.setAutoCommit(false);
>       // select Blob for update
>       PreparedStatement stmt = conn.prepareStatement(
>             "SELECT PICTURE FROM PEOPLE WHERE SEQ_ID=? FOR UPDATE OF PICTURE");
>       stmt.setInt(1, 1);
>       ResultSet rs = stmt.executeQuery();
>       // get Blob output stream
>       rs.next();
>       Blob blob = rs.getBlob(1);
>       java.io.OutputStream outstream = blob.setBinaryStream(1l);
>       // copy the input file to the Blob in chunks of 1K
>       byte[] buf = new byte[1024];
>       int count;
>       while (-1 != (count = instream.read(buf))) {
>          outstream.write(buf, 0, count);
>          System.out.println("Written " + count + " bytes to Blob");
>       }
>       // close streams
>       instream.close();
>       outstream.close();
>       // update Blob with new value
>       String cursor = rs.getCursorName();
>       PreparedStatement stmt2 = conn.prepareStatement(
>             "UPDATE PEOPLE SET PICTURE=? WHERE CURRENT OF " + cursor);
>       stmt2.setBlob(1, blob);
>       stmt2.executeUpdate();
>       // clean up
>       stmt2.close();
>       stmt.close();
>       conn.commit();
>       conn.close();
>    }
> }

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