Re: AW: [dbforms] Avoiding FileHolder to store BLOBs

[Luca Fossato]

Hi!

Shawn wrote:
Apologies again,

I knew I didn't really have a handle on the answer and was just trying 
to move the discussion along.

Luca pointed out a way to get it from the database as a java object.
It's also possible to marshall the FileHolder class into an 
XML stream (that contains also binary data?) and store it 
into the database.
I suppose other languages could retrieve the xml stream, 
parse it and retrieve the required data.

example:
JSX
http://www.csse.monash.edu.au/~bren/JSX/
http://www.csse.monash.edu.au/~bren/JSX/tech.html
I did a simple utility class with  marshall / unmarshall 
methods... in attachment (maybe it could be useful...)

my .02 euro, as well ;^)

Regards,
Luca

As for non java applications accessing Blobs retrieved from the database 
via dbforms, YOU WANT TO KNOW IF THAT IS POSSIBLE.

I don't know of a way.  If anyone does, please let me know so I can 
document it in the UsersGuide.

As for the question of whether time should be invested into making it 
possible (if it is not now), it is a good question to ask.  IS IT 
NECESSARY FOR PEOPLE TO ACCESS BLOBS FROM NON-JAVA APPLICATIONS?

Does the "build it and somebody will find a use" rule apply?


What happens if a C++/PHP/Perl/TCL/Ruby/.NET/Jelly/XYZ application 
tries to access this BLOB. It actually DOES NOT contain the binary 
content I passed but a serialized FileHolder. And non-Java languages 
might have a problem processing a serialized Java objects

package com.pow2.blablah.util;
import java.io.*;
import java.util.*;

import org.apache.log4j.Category;

import JSX.*;


/**
 *  JSX Helper class.
 *  <br>
 *  See <code>http://www.csse.monash.edu.au/~bren/JSX/tech.html</code>
 *  for further informations.
 *
 * @author  Luca Fossato
 * @created  15 maggio 2002
 */
public class MarshallerUtil
{
  private static Category cat = Category.getInstance(MarshallerUtil.class);


  /**
   *  Trasform the input XML String into a Java object.
   *
   * @param  str the String containing the Java object XML description
   * @return the Java object
   * @exception Exception if any error occurs
   */
  public static Object unMarshallObject(String str) throws Exception
  {
    ByteArrayInputStream bis = null;
    ObjIn                in  = null;
    Object               obj = null;

    try
    {
      bis = new ByteArrayInputStream(str.getBytes());
      in  = new ObjIn(bis);
      obj = in.readObject();
    }
    finally
    {
      if (in  != null) in.close();
      if (bis != null) bis.close();
    }

    return obj;
  }


  /**
   *  Trasform the input object into an XSL String.
   *
   * @param   obj the object to transform
   * @return  the XML String representation of the input object
   */
  public static String marshallObject(Object obj) throws Exception
  {
    StringWriter sw  = null;
    ObjOut       out = null;
    String       s   = null;

    try
    {
      sw  = new StringWriter();
      out = new ObjOut(new PrintWriter(new BufferedWriter(sw), true));
      out.writeObject(obj);
      s = sw.toString();
    }
    finally
    {
      if (out != null) out.close();
      if (sw  != null) sw.close();
    }

    return s;
  }
}