CompositeProxyFactory.java

biz/hammurapi/util/CompositeProxyFactory.java

Violations

Inspector Message Severity Location
Java Inspector 002 Empty catch block. 1 90:59
Java Inspector 048 Copyrights information should be present in each file. 1
Java Inspector 089 Type is not documented 2 44:9
Java Inspector 089 Undocumented parameter classLoader 2 73:9
Java Inspector 089 Undocumented method 2 78:9
Java Inspector 089 Undocumented method 2 83:41
Java Inspector 089 Undocumented method 2 101:9
Java Inspector 026 Avoid hardwired string literals. Allowed literals: [] 3 95:81
Java Inspector 046 Empty statements 3 90:91

Source code

1/*
2 * hgcommons 9
3 * Hammurapi Group Common Library
4 * Copyright (C) 2003  Hammurapi Group
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
19 *
20 * URL: http://www.hammurapi.biz/hammurapi-biz/ef/xmenu/hammurapi-group/products/products/hgcommons/index.html
21 * e-Mail: support@hammurapi.biz
22 */
23package biz.hammurapi.util;
24
25import java.lang.reflect.InvocationHandler;
26import java.lang.reflect.Method;
27import java.lang.reflect.Proxy;
28
29/**
30 * Creates a proxy which combines several classes and sequentially searches for
31 * matching method to invoke. This allows to implement lazy instantiation for
32 * situations where you have part of object data in cheaply accessible storage (cache or DB)
33 * and the other part in expensively accessible storage (e.g. XML file shall be
34 * parsed to access all object data).
35 * @author Pavel Vlasov
36 * @version $Revision: 1.1 $
37 */
38public class CompositeProxyFactory {
39	
40	/**
41	 * @author Pavel Vlasov
42	 * @version $Revision: 1.1 $
43	 */
44	public interface TargetFactory {
45		
46		/**
47		 * @return target class for the proxy to know which methods it implements.
48		 * You might want to return only one of class interfaces or base classes
49		 * to limit number of exposed methods.
50		 */
51		Class getTargetClass();
52		
53		/**
54		 * @return target itself to perform invocation.
55		 */
56		Object getTarget();
57	}
58	
59	private ClassLoader classLoader;
60
61	/**
62	 * Creates factory which uses default classloader.
63	 */
64	public CompositeProxyFactory() {
65		super();
66		classLoader=getClass().getClassLoader();
67	}
68	
69	/**
70	 * Creates factory whith specified classloader which will be
71	 * passed to createProxy(ClassLoader, Class[], TargetFactory[])
72	 */
73	public CompositeProxyFactory(ClassLoader classLoader) {
74		super();
75		this.classLoader=classLoader;
76	}
77	
78	public static Object createProxy(ClassLoader classLoader, Class[] interfaces, final TargetFactory[] targetFactories) {
79		return Proxy.newProxyInstance(
80				classLoader, 
81				interfaces, 
82				new InvocationHandler() {
83					public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
84						for (int i=0; i<targetFactories.length; i++) {
85							try {
86								return targetFactories[i]
87									.getTargetClass()
88									.getMethod(method.getName(), method.getParameterTypes())
89									.invoke(targetFactories[i].getTarget(), args);
90							} catch (NoSuchMethodException e) {
91								// Ignore it.

92							}
93						}
94						
95						throw new NoSuchMethodException("Method not found in targets: "+method);
96					}					
97				});
98		
99	}
100	
101	public Object createProxy(Class[] interfaces, TargetFactory[] targetFactories) {
102		return createProxy(classLoader, interfaces, targetFactories);		
103	}	
104}
105