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
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
|
/*****************************************************************************
* Copyright (c) 2016 Christian W. Damus and others.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Christian W. Damus - Initial API and implementation
*
*****************************************************************************/
package org.eclipse.papyrus.infra.tools.util;
import java.lang.reflect.Array;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.BinaryOperator;
import java.util.stream.Stream;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.util.tracker.ServiceTracker;
/**
* A service tracker that provides a single service as a composite of
* registered service implementations.
*/
public class CompositeServiceTracker<S> extends ServiceTracker<S, S> {
private final AtomicReference<S> delegate = new AtomicReference<>();
private final Class<S> serviceType;
private final S identity;
private final BinaryOperator<S> composer;
/**
* Initializes me with the bundle context in which I track resolver services,
* an identity service that generally performs trivially (e.g., no-ops or default behaviour),
* and an operator that composes two service instances.
*
* @param context
* the bundle context
* @param serviceType
* the service protocol type
* @param identity
* the basic no-op or default service instance
* @param composer
* an operator that composes two services instances into one
*/
public CompositeServiceTracker(BundleContext context, Class<S> serviceType, S identity, BinaryOperator<S> composer) {
super(context, serviceType, null);
this.serviceType = serviceType;
this.identity = identity;
this.composer = composer;
}
@Override
public final S getService() {
S result = this.delegate.get();
if (result == null) {
// Recompute
@SuppressWarnings("unchecked")
S[] services = (S[]) Array.newInstance(serviceType, getTrackingCount());
result = Stream.of(getServices(services))
.filter(Objects::nonNull) // If the array has more slots than we have services
.reduce(identity, composer);
this.delegate.set(result);
}
return result;
}
@Override
public S addingService(ServiceReference<S> reference) {
S result = super.addingService(reference);
// We will have to recompute our delegates
delegate.set(null);
return result;
}
@Override
public void removedService(ServiceReference<S> reference, S service) {
super.removedService(reference, service);
// We will have to recompute our delegates
delegate.set(null);
}
}
|
