Postgres save images

CREATE TABLE images (name text, img bytea);

 File file = new File("image.gif");
 FileInputStream fis = new FileInputStream(file);
 PreparedStatement ps = conn.prepareStatement("INSERT INTO images VALUES (?, ?)");
 ps.setString(1, file.getName());
 ps.setBinaryStream(2, fis, file.length());
 ps.executeUpdate();
 ps.close();
 fis.close();

setBinaryStream(), transfers a set number of bytes from a stream.
setBytes(), use this method if the contents of the image was already in a byte[].

Retrieving image

  PreparedStatement ps = conn.prepareStatement("SELECT img FROM images WHERE name=?");
  ps.setString(1, "image.gif");
  ResultSet rs = ps.executeQuery();
  if(rs.next()) {
         byte[] imgBytes = rs.getBytes(1);
  }
  rs.close();
 }
 ps.close();

You could have used a InputStream object instead.

Alternatively you could be storing a very large file and want to use the LargeObject API to store the file:

CREATE TABLE imagesLO (imgname text, imgOID OID);

To insert an image, you would use:

 conn.setAutoCommit(false); // All LargeObject API calls must be within a transaction
 
 LargeObjectManager lobj = ((org.postgresql.PGConnection)conn).getLargeObjectAPI();
 
 //create a new large object
 int oid = lobj.create(LargeObjectManager.READ | LargeObjectManager.WRITE);
 
 //open the large object for write
 LargeObject obj = lobj.open(oid, LargeObjectManager.WRITE);
 
 // Now open the file
 File file = new File("image.gif");
 FileInputStream fis = new FileInputStream(file);
 
 // copy the data from the file to the large object
 byte buf[] = new byte[2048];
 int s, tl = 0;
 while ((s = fis.read(buf, 0, 2048)) > 0)
 {
 obj.write(buf, 0, s);
 tl += s;
 }
 
 obj.close();
 
 //Now insert the row into imagesLO
 PreparedStatement ps = conn.prepareStatement("INSERT INTO imagesLO VALUES (?, ?)");
 ps.setString(1, file.getName());
 ps.setInt(2, oid);
 ps.executeUpdate();
 ps.close();
 fis.close();

Retrieving the image from the Large Object:

 conn.setAutoCommit(false);
 
 // Get the Large Object Manager to perform operations with
 LargeObjectManager lobj = ((org.postgresql.PGConnection)conn).getLargeObjectAPI();
 
 PreparedStatement ps = con.prepareStatement("SELECT imgOID FROM imagesLO WHERE imgname=?");
 ps.setString(1, "image.gif");
 ResultSet rs = ps.executeQuery();
 if (rs.next()) 
 {
  int oid = rs.getInt(1);//open the large object for reading
 LargeObject obj = lobj.open(oid, LargeObjectManager.READ);
 
 //read the data
 byte buf[] = new byte[obj.size()];
 obj.read(buf, 0, obj.size());
 //do something with the data read here
 obj.close();
 }
     rs.close();
 }
 ps.close();