Byte[] serialization/deserialization BLOB problem

Question

I want to store an image in DB.
I choose to store a byte[], like a BLOB (i use MySql).
But when byte[] is serialized in DB in front of the array are inserted 27
bytes.
What should i do to store exact the given byte array ?
(Or off course an ImageIcon object : for which on deserialization an
ClassCastException is thrown).
And which is the reason that those 27 (!?!) bytes are inserted.
thank you in advance for your help.
(please excuse my english)
BytesTest.jdo
<?xml version="1.0"?>
<!DOCTYPE jdo SYSTEM "http://www.solarmetric.com/dtds/jdo.dtd">
<!-- This JDO Metadata file was auto-generated on 7/2/02 3:18 PM.
See http://www.solarmetric.com for Kodo JDO Documentation and examples. -->
<jdo>
<package name="jdoproject">
<class name="BytesTest" requires-extent="true">
<field name="bytesArray" null-value="none" primary-key="false">
<extension key="blob" value="true" vendor-name="kodo"/>
</field>
</class>
</package>
</jdo>
BytesTest.java
package jdoproject;
public class BytesTest {
private byte[] bytesArray = null;
public BytesTest () {
bytesArray = new byte[30];
for (int i = 0; i < 30; i++)
bytesArray[i] = (byte)(65 + i);
public String toString () {
StringBuffer sb = new StringBuffer();
for (int i = 0; i < bytesArray.length; i++)
sb.append(" " + (bytesArray[i] & 0xFF) + "[" +
(char)(bytesArray[i] & 0xFF)
+ "]");
return sb.toString();
this must be run twice (first , to make an insertion , second to view what
is previos inserted)
BytesTestMain.java
public class BytesTestMain {
public static void main (String[] args) {
BytesTest test = null;
try {
JDBCConfiguration jc = new JDBCPropertiesConfiguration();
PersistenceManagerFactory pmf = new
JDBCPersistenceManagerFactory(
new FileInputStream("config/kodo.properties"));
PersistenceManager pm = pmf.getPersistenceManager();
Extent people = pm.getExtent(BytesTest.class, false);
Query query = pm.newQuery(BytesTest.class, people);
Collection result = (Collection)query.execute();
Iterator iter = result.iterator();
System.out.println("Found items: ");
while (iter.hasNext()) {
test = (BytesTest)iter.next();
System.out.println("test= " + test);
test = new BytesTest();
System.out.println("Inserting item: "+test);
Transaction t = pm.currentTransaction();
t.begin();
pm.makePersistent(test);
t.commit();
} catch (Exception e) {
e.printStackTrace();
System.out.println("ALL DONE---------------------");

Answer 1

cross-post:
http://forum.java.sun.com/thread.jsp?forum=31&thread=323525