Hibernate - Store a column as encrypted, and decrypt only on runtime

I have a database column that needs to be encrypted, when passed from a hibernate backed webapp. The webapp is on tomcat 6, Hibernate 4, and Mysql as the backing store.

The problem however is that the password to encrypt/decrypt this field will only be available at runtime of the program. Initially I had hoped to use the AES_ENCRYPT/DECRYPT methods, outlined quite well here:

DataBase encryption in Hibernate

and here:

http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/mapping.html#mapping-column-read-and-write

(Though this does refer to version 3.6 of hibernate, I believe it should be the same in 4.0).

However, since this uses the following notation:

@Column(columnDefinition= "LONGBLOB", name="encryptedBody") 
@ColumnTransformer(
  read="AES_DECRYPT(encryptedBody, 'password')", 
  write="AES_ENCRYPT(?, 'password')")
public byte[]  getEncryptedBody() {
    return encryptedBody;
}

public void setEncryptedBody(byte[]  encryptedBody) {
    this.encryptedBody = encryptedBody;
}

This requires that the password be specified in the annotation itself, and cannot be a variable.

Is there a way to use the database methods through hibernate in this manner, but with the password as a variable? Is there a better approach?