001: /*
002: * ====================================================================
003: * JAFFA - Java Application Framework For All
004: *
005: * Copyright (C) 2002 JAFFA Development Group
006: *
007: * This library is free software; you can redistribute it and/or
008: * modify it under the terms of the GNU Lesser General Public
009: * License as published by the Free Software Foundation; either
010: * version 2.1 of the License, or (at your option) any later version.
011: *
012: * This library is distributed in the hope that it will be useful,
013: * but WITHOUT ANY WARRANTY; without even the implied warranty of
014: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015: * Lesser General Public License for more details.
016: *
017: * You should have received a copy of the GNU Lesser General Public
018: * License along with this library; if not, write to the Free Software
019: * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
020: *
021: * Redistribution and use of this software and associated documentation ("Software"),
022: * with or without modification, are permitted provided that the following conditions are met:
023: * 1. Redistributions of source code must retain copyright statements and notices.
024: * Redistributions must also contain a copy of this document.
025: * 2. Redistributions in binary form must reproduce the above copyright notice,
026: * this list of conditions and the following disclaimer in the documentation
027: * and/or other materials provided with the distribution.
028: * 3. The name "JAFFA" must not be used to endorse or promote products derived from
029: * this Software without prior written permission. For written permission,
030: * please contact mail to: jaffagroup@yahoo.com.
031: * 4. Products derived from this Software may not be called "JAFFA" nor may "JAFFA"
032: * appear in their names without prior written permission.
033: * 5. Due credit should be given to the JAFFA Project (http://jaffa.sourceforge.net).
034: *
035: * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED
036: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
037: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
038: * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
039: * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
040: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
041: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
042: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
043: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
044: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
045: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
046: * SUCH DAMAGE.
047: * ====================================================================
048: */
049:
050: package org.jaffa.persistence.engines.jdbcengine.proxy;
051:
052: import java.lang.reflect.InvocationHandler;
053: import java.lang.reflect.Proxy;
054: import org.jaffa.persistence.IPersistent;
055:
056: /** This class is a factory for obtaining IPersistent instances.
057: */
058: public class PersistentInstanceFactory {
059:
060: /** Generates an appropriate instance for the input persistentClass.
061: * If the persistentClass is a 'Class', then it should implement the 'IPersistent' interface. The persistence engine will simply instantiate the class.
062: * If the persistentClass is an 'Interface', then the persistence engine will generate a dynamic proxy, to implement the IPersistent and the 'persistentClass' interfaces.
063: * A RuntimeException will be thrown if any error occurs during instantiation.
064: * @param persistentClass The actual persistentClass which can represent a 'Class' or an 'Interface'
065: * @return an instance implementing the IPersistent interface.
066: */
067: public static IPersistent newPersistentInstance(
068: Class persistentClass) {
069: try {
070: if (persistentClass.isInterface()) {
071: Class[] interfaces = IPersistent.class
072: .isAssignableFrom(persistentClass) ? new Class[] { persistentClass }
073: : new Class[] { IPersistent.class,
074: persistentClass };
075: return (IPersistent) Proxy.newProxyInstance(
076: persistentClass.getClassLoader(), interfaces,
077: new PersistentInstanceInvocationHandler(
078: persistentClass));
079: } else {
080: return (IPersistent) persistentClass.newInstance();
081: }
082: } catch (Exception e) {
083: throw new RuntimeException(
084: "Error in instantiating a persistent class", e);
085: }
086: }
087:
088: /** This is a helper method to determine the actual class which was used to create an IPersistent instance.
089: * It is quite possible that the input object is a dynamic proxy.
090: * @param object The object which implements the IPersistent instance.
091: * @return The class which was used for instantiating the instance.
092: */
093: public static Class getActualPersistentClass(IPersistent object) {
094: Class clazz = object.getClass();
095: if (Proxy.isProxyClass(clazz)) {
096: Class[] interfaces = clazz.getInterfaces();
097: for (int i = 0; i < interfaces.length; i++) {
098: if (interfaces[i] != IPersistent.class) {
099: clazz = interfaces[i];
100: break;
101: }
102: }
103: }
104: return clazz;
105: }
106:
107: /** This is used by the MoldingService to initialize the Persistent instance.
108: * This will merely add the attribute/value to the Map in the PersistentInstanceInvocationHandler.
109: * This will bypass the validations performed during invocation of the setXyz() method on the persistent object.
110: * Nothing will be done if the input object is not a Proxy or if its InvocationHandler is not an instance of PersistentInstanceInvocationHandler.
111: * @param object The Proxy object for an IPersistence interface.
112: * @param attributeName The attribute whose value will be set.
113: * @param value The value to be set.
114: */
115: public static void setInstanceValue(IPersistent object,
116: String attributeName, Object value) {
117: if (Proxy.isProxyClass(object.getClass())) {
118: InvocationHandler handler = Proxy
119: .getInvocationHandler(object);
120: if (handler instanceof PersistentInstanceInvocationHandler)
121: ((PersistentInstanceInvocationHandler) handler)
122: .addAttributeValue(attributeName, value);
123: }
124: }
125:
126: }
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