At 10:36 2002-12-04 +0100, you wrote:
Hi allhi again,
i've been looking through the tutorials to do inheritance mapping of a whole inheritance tree in a single table
and i've seen that it is _required_ to have a field in the objects that contains the class name ...
why is it so ?
shouldn't it be possible to tell OJB to call getClass().getName() on its own for the FieldDescriptor storing the instance type in db ?
has somebody thought a solution for this (e.g. write a PersistentField implemenation that can do it) ?
Thanks for your time
David
actually i've been thinking of a possible PersistentField implementation (see attached file)
it seems very simple, (so simple it feels weird ;) )
what do you think ?
thanks
David
package com.sysdeo.framework.persistencelayer.objectbridge;
/* ==================================================================== * The Apache Software License, Version 1.1 * * Copyright (c) 2001 The Apache Software Foundation. All rights * reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. The end-user documentation included with the redistribution, * if any, must include the following acknowledgment: * "This product includes software developed by the * Apache Software Foundation (http://www.apache.org/)." * Alternately, this acknowledgment may appear in the software itself, * if and wherever such third-party acknowledgments normally appear. * * 4. The names "Apache" and "Apache Software Foundation" and * "Apache ObjectRelationalBridge" must not be used to endorse or promote products * derived from this software without prior written permission. For * written permission, please contact [EMAIL PROTECTED] * * 5. Products derived from this software may not be called "Apache", * "Apache ObjectRelationalBridge", nor may "Apache" appear in their name, without * prior written permission of the Apache Software Foundation. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. */ import java.lang.reflect.Field; import java.security.AccessController; import java.security.PrivilegedAction; import org.apache.ojb.broker.metadata.ClassDescriptor; import org.apache.ojb.broker.metadata.MetadataException; import org.apache.ojb.broker.metadata.PersistentField; import org.apache.ojb.broker.metadata.PersistentFieldDefaultImpl; import org.apache.ojb.broker.util.logging.Logger; import org.apache.ojb.broker.util.logging.LoggerFactory; /** * This class is a wrapper around java.lang.reflect.Field objects. * @author <a href="mailto:[EMAIL PROTECTED]";>Thomas Mahler<a> * @version $Id: PersistentFieldDynamicClassNameImpl.java,v 1.8 2002/09/21 15:49:37 brj Exp $ */ public class PersistentFieldDynamicClassNameImpl extends PersistentFieldDefaultImpl { public PersistentFieldDynamicClassNameImpl(Field f) { super(f); } public PersistentFieldDynamicClassNameImpl(Class c, String fieldname) { super(c, fieldname); } /** * Sets the field represented by this PersistentField object on the specified object argument to the specified new value. * The new value is automatically unwrapped if the underlying field has a primitive type. * This implementation invokes set() on its underlying Field object if the argument <b>is not null</b>. * OBS IllegalArgumentExceptions are wrapped as PersistenceBrokerExceptions. * * @throws MetadataException if there is an error setting this field value on obj * @see java.lang.reflect.Field */ public void set(Object obj, Object value) { if (!isConcreteClassField()) { super.set(obj, value); } } /** * Returns the value of the field represented by this PersistentField, on the specified object. * This implementation invokes get() on its underlying Field object. * * @param obj - the object instance which we are trying to get the field value from * @throws MetadataException if there is an error getting this field value from obj * @see java.lang.reflect.Field */ public Object get(Object obj) { if (isConcreteClassField()) { return obj.getClass().getName(); } else { return super.get(obj); } } /** * Determines whether this field represent the OJB special field that contains * the concrete class name if persistent storage * This implementation checks the field name with the {@link ClassDescriptor#OJB_CONCRETE_CLASS} value. * * @param obj - the object instance which we are trying to get the field value from */ private boolean isConcreteClassField() { return ClassDescriptor.OJB_CONCRETE_CLASS.equals(getField().getName()); } }
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