Williamson, Nick wrote:
Hi all,
In Oracle, when you want to update a BLOB, you have to do this first:
set my_blob_column=empty_blob();
...which initializes it and opens it up for writing. Oracle has a
concept of a "locator", which I guess is similar to a pointer or
handle to the BLOB object, and it is required in order to start
streaming data to it. Just setting my_blob_column=null doesn't do the
same thing.
Anyway, I'm trying to port this currently-Oracle app to Derby and of
course Derby doesn't like the reference to empty_blob(). Can someone
put me in the picture regarding the way in which you initialize BLOBs
for update in Derby, maybe posting a code sample or a link to the
relevant docs? I've had a quick scan through the docs and Google
without much success...
TIA
Nick
Hope this helps:
import java.sql.*;
// create table t_lob1_log(oldvalue varchar(80), newvalue varchar(80),
chng_time timestamp default current_timestamp);
// Loads the contents of the file into the BLOB column
public class blob_insert
{
public static void main(String[] args) {
String filename = "cheesecake.bmp";
try {
String url = "jdbc:derby:101toursDB";
Class.forName("org.apache.derby.jdbc.EmbeddedDriver").newInstance();
Connection conn = DriverManager.getConnection(url);
Statement s = conn.createStatement();
// s.executeUpdate("create table LOB1 (str1 Varchar(80),
b_lob BLOB(50M))");
// conn.commit();
// --- add a file
java.io.File file = new java.io.File(filename);
int fileLength = (int) file.length();
// - first, create an input stream
java.io.InputStream fin = new java.io.FileInputStream(file);
PreparedStatement ps = conn.prepareStatement("INSERT INTO
LOB1 VALUES (?, ?)");
ps.setString(1, filename);
// - set the value of the input parameter to the input stream
ps.setBinaryStream(2, fin, fileLength);
ps.execute();
conn.commit();
// --- reading the columns - print: converts BLOB to
meaninless String
ResultSet rs = s.executeQuery("SELECT * FROM LOB1 WHERE str1
= '" + filename +"'");
while (rs.next()) {
java.sql.Blob ablob = rs.getBlob(2);
java.io.InputStream ip = rs.getBinaryStream(2);
int c = ip.read();
while (c > 0) {
System.out.print((char)c);
c = ip.read();
}
System.out.print("\n");
// ...
}
} catch (Exception e) {
System.out.println("Error! "+e);
}
}
}
