1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
|
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.ex.variablespeed;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* Contains a utility method for adapting a given interface against a real implementation.
* <p>
* This class is thead-safe.
*/
public class DynamicProxy {
/**
* Dynamically adapts a given interface against a delegate object.
* <p>
* For the given {@code clazz} object, which should be an interface, we return a new dynamic
* proxy object implementing that interface, which will forward all method calls made on the
* interface onto the delegate object.
* <p>
* In practice this means that you can make it appear as though {@code delegate} implements the
* {@code clazz} interface, without this in practice being the case. As an example, if you
* create an interface representing the {@link android.media.MediaPlayer}, you could pass this
* interface in as the first argument, and a real {@link android.media.MediaPlayer} in as the
* second argument, and now calls to the interface will be automatically sent on to the real
* media player. The reason you may be interested in doing this in the first place is that this
* allows you to test classes that have dependencies that are final or cannot be easily mocked.
*/
// This is safe, because we know that proxy instance implements the interface.
@SuppressWarnings("unchecked")
public static <T> T dynamicProxy(Class<T> clazz, final Object delegate) {
InvocationHandler invoke = new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
return delegate.getClass()
.getMethod(method.getName(), method.getParameterTypes())
.invoke(delegate, args);
} catch (InvocationTargetException e) {
throw e.getCause();
}
}
};
return (T) Proxy.newProxyInstance(clazz.getClassLoader(), new Class<?>[] { clazz }, invoke);
}
}
|
