Converting a RenderedOp to a BLOB

Question

Hi
I have a database which stores images as BLOBS, I have no problem storing the images when I have the image file initially, however when I load the BLOB from the database to my Java application I allow people to modify the image which is converted to a RenderedOp, I want to be able to save this manipulated image to the database but obviously have no filename for the image, I was wondering is it possible to store this RenderedOp as a BLOB and if so how to do so?
Cheers
Richie

Answer 1

BLOBS are a bit of a nightmare in JDBC. The Blob interface looks like it was designed by someone who didn't know what BLOBs are. In particular there's no method of creating a new java.sql.Blob, you can only retrive one from a database query.
What I do for Postgress is to write my own implementation of java.sql.Blob which reads from a file when the driver does a getBinaryStream on it. Then setBlob on a PreparedStatement seems to store OK, at least on Postgress creating a new record.
This is my "fake" Blob
* FileBlob.java
* Created on 06 April 2004, 09:00
package org.figis.util;
import java.io.InputStream;
import java.sql.Blob;
import java.sql.SQLException;
* <p>{@link java.sql.Blob} object for inserting new BLOB into database from file.</p>
* <p>This, to my mind, is a fairly ugly fudge to get arround the complete
* ommision of a capability from JDBC. The alternative, in the case of Postgres,
* is to access a proprietary interface.<p>
* <p>When an instance of this class is supplied to a {@link java.sql.PreparedStatement}
* Postgres (at least) creates a new Blob and copies the stream obtained from getBinaryStream()
* into it, then it puts the BLOB reference into the SQL.<p>
* <p>This might, or might not work with other databases.</p>
* @version $Id: FileBlob.java,v 1.3 2004/07/28 16:49:00 malcolmm Exp $
* @see java.sql.Blob
   @see java.sql.PreparedStatement
* @author  malcolm
public class FileBlob implements Blob {
    InputStream stream;
    long size;
     * Creates a new instance of FileBlob
     * @param stream Input stream with data
     * @param size Length of data
    public FileBlob(InputStream stream, long size) {
        this.stream = stream;
        this.size = size;
     * Create a new instance of FileBlob from a File object
     * @param file The existing file to copy
     * @throws IOException if file cannot be openned.
    public FileBlob(java.io.File file) throws java.io.IOException {
        this(new java.io.FileInputStream(file), file.length());
    /** Gets a stream containing the file data.
     * @throws SQLException Wrapped IO exception should file be duff
     * @return An inputStream
    public InputStream getBinaryStream() throws SQLException {
        return stream;
    /** Unsupported
     * @param pos start position
     * @param length bytes to read
     * @throws SQLException On read error
     * @return byte array
    public byte[] getBytes(long pos, int length) throws SQLException {
        throw new UnsupportedOperationException("getBytes");
    /** Get size of input data
     * @throws SQLException Retrieval error
     * @return Size in bytes
    public long length() throws SQLException {
        return size;
    /** Unsupported
     * @param pattern Pattern to find
     * @param start search start
     * @throws SQLException On access error
     * @return position
    public long position(byte[] pattern, long start) throws SQLException {
        throw new UnsupportedOperationException("position");
    public long position(Blob pattern, long start) throws SQLException {
        throw new UnsupportedOperationException("position");
    public java.io.OutputStream setBinaryStream(long pos) throws SQLException {
        throw new UnsupportedOperationException("setBinaryStream");
    public int setBytes(long pos, byte[] bytes) throws SQLException {
        throw new UnsupportedOperationException("setBytes");
    public int setBytes(long pos, byte[] bytes, int offset, int len) throws SQLException {
        throw new UnsupportedOperationException("setBytes");
    public void truncate(long len) throws SQLException {
        throw new UnsupportedOperationException("truncate");