KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > apache > ojb > broker > core > proxy > VirtualProxy


1 package org.apache.ojb.broker.core.proxy;
2
3 /* Copyright 2002-2005 The Apache Software Foundation
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17
18 import java.io.Serializable JavaDoc;
19
20 import org.apache.ojb.broker.Identity;
21 import org.apache.ojb.broker.PBKey;
22 import org.apache.ojb.broker.PersistenceBrokerException;
23
24 /**
25  * Proxy base class. can be used to implement lazy materialization techniques.
26  *
27  * @author <a HREF="mailto:thomas.mahler@itellium.com">Thomas Mahler<a>
28  * @version $Id: VirtualProxy.java,v 1.1.2.6 2005/12/21 22:25:30 tomdz Exp $
29  */
30 public abstract class VirtualProxy implements OJBProxy,Serializable JavaDoc
31 {
32     static final long serialVersionUID = -3999451313262635171L;
33
34     /**
35      * reference to the IndirectionHandler that encapsulates the delegation mechanism
36      * */
37     private IndirectionHandler indirectionHandler = null;
38
39     /**
40      * Creates a new, uninitialized proxy.
41      */
42     public VirtualProxy()
43     {}
44
45     /**
46      * Creates a VirtualProxy for the subject with the given identity.
47      *
48      * @param key The key of the PersistenceBroker
49      * @param oid The identity of the subject
50      */
51     public VirtualProxy(PBKey key, Identity oid)
52     {
53         indirectionHandler = AbstractProxyFactory.getProxyFactory().createIndirectionHandler(key, oid);
54     }
55
56     /**
57      * Create a VirtualProxy that uses the given invocation handler.
58      * [tomdz] Why here the use of InvocationHandler ?
59      *
60      * @param handler The indirection handler of the proxy
61      *
62      */
63     
64     public VirtualProxy(IndirectionHandler handler)
65     {
66         indirectionHandler = handler;
67     }
68
69     /**
70      * Returns the indirection handler of the given proxy.
71      *
72      * @param proxy The proxy
73      * @return The indirection handler
74      */
75     public static IndirectionHandler getIndirectionHandler(VirtualProxy proxy)
76     {
77         return proxy.indirectionHandler;
78     }
79
80     /**
81      * Determines whether this proxy already has been materialized.
82      *
83      * @return <code>true</code> if the real subject already been loaded
84      */
85     public boolean alreadyMaterialized()
86     {
87         return indirectionHandler.alreadyMaterialized();
88     }
89
90
91     /**
92      * Returns the proxies real subject. The subject will be materialized if necessary.
93      *
94      * @return The subject
95      */
96     public Object JavaDoc getRealSubject() throws PersistenceBrokerException
97     {
98         return indirectionHandler.getRealSubject();
99     }
100     
101     /**
102      * Returns the IndirectionHandler
103      *
104      * @return The indirectionHandler
105      */
106     public IndirectionHandler getIndirectionHandler()
107     {
108         return indirectionHandler;
109     }
110
111     /**
112      * Returns the identity of the subject.
113      *
114      * @return The identity
115      */
116     Identity getIdentity()
117     {
118         return indirectionHandler.getIdentity();
119     }
120     
121     public Object JavaDoc writeReplace()
122     {
123         return this;
124     }
125     
126
127 }
128
Popular Tags