1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.server;
18
19import android.content.Context;
20import android.os.IBinder;
21import android.os.ServiceManager;
22
23/**
24 * The base class for services running in the system process. Override and implement
25 * the lifecycle event callback methods as needed.
26 * <p>
27 * The lifecycle of a SystemService:
28 * </p><ul>
29 * <li>The constructor is called and provided with the system {@link Context}
30 * to initialize the system service.
31 * <li>{@link #onStart()} is called to get the service running.  The service should
32 * publish its binder interface at this point using
33 * {@link #publishBinderService(String, IBinder)}.  It may also publish additional
34 * local interfaces that other services within the system server may use to access
35 * privileged internal functions.
36 * <li>Then {@link #onBootPhase(int)} is called as many times as there are boot phases
37 * until {@link #PHASE_BOOT_COMPLETED} is sent, which is the last boot phase. Each phase
38 * is an opportunity to do special work, like acquiring optional service dependencies,
39 * waiting to see if SafeMode is enabled, or registering with a service that gets
40 * started after this one.
41 * </ul><p>
42 * NOTE: All lifecycle methods are called from the system server's main looper thread.
43 * </p>
44 *
45 * {@hide}
46 */
47public abstract class SystemService {
48    /*
49     * Boot Phases
50     */
51    public static final int PHASE_WAIT_FOR_DEFAULT_DISPLAY = 100; // maybe should be a dependency?
52
53    /**
54     * After receiving this boot phase, services can obtain lock settings data.
55     */
56    public static final int PHASE_LOCK_SETTINGS_READY = 480;
57
58    /**
59     * After receiving this boot phase, services can safely call into core system services
60     * such as the PowerManager or PackageManager.
61     */
62    public static final int PHASE_SYSTEM_SERVICES_READY = 500;
63
64    /**
65     * After receiving this boot phase, services can broadcast Intents.
66     */
67    public static final int PHASE_ACTIVITY_MANAGER_READY = 550;
68
69    /**
70     * After receiving this boot phase, services can start/bind to third party apps.
71     * Apps will be able to make Binder calls into services at this point.
72     */
73    public static final int PHASE_THIRD_PARTY_APPS_CAN_START = 600;
74
75    /**
76     * After receiving this boot phase, services can allow user interaction with the device.
77     * This phase occurs when boot has completed and the home application has started.
78     * System services may prefer to listen to this phase rather than registering a
79     * broadcast receiver for ACTION_BOOT_COMPLETED to reduce overall latency.
80     */
81    public static final int PHASE_BOOT_COMPLETED = 1000;
82
83    private final Context mContext;
84
85    /**
86     * Initializes the system service.
87     * <p>
88     * Subclasses must define a single argument constructor that accepts the context
89     * and passes it to super.
90     * </p>
91     *
92     * @param context The system server context.
93     */
94    public SystemService(Context context) {
95        mContext = context;
96    }
97
98    /**
99     * Gets the system context.
100     */
101    public final Context getContext() {
102        return mContext;
103    }
104
105    /**
106     * Returns true if the system is running in safe mode.
107     * TODO: we should define in which phase this becomes valid
108     */
109    public final boolean isSafeMode() {
110        return getManager().isSafeMode();
111    }
112
113    /**
114     * Called when the dependencies listed in the @Service class-annotation are available
115     * and after the chosen start phase.
116     * When this method returns, the service should be published.
117     */
118    public abstract void onStart();
119
120    /**
121     * Called on each phase of the boot process. Phases before the service's start phase
122     * (as defined in the @Service annotation) are never received.
123     *
124     * @param phase The current boot phase.
125     */
126    public void onBootPhase(int phase) {}
127
128    /**
129     * Called when a new user is starting, for system services to initialize any per-user
130     * state they maintain for running users.
131     * @param userHandle The identifier of the user.
132     */
133    public void onStartUser(int userHandle) {}
134
135    /**
136     * Called when switching to a different foreground user, for system services that have
137     * special behavior for whichever user is currently in the foreground.  This is called
138     * before any application processes are aware of the new user.
139     * @param userHandle The identifier of the user.
140     */
141    public void onSwitchUser(int userHandle) {}
142
143    /**
144     * Called when an existing user is stopping, for system services to finalize any per-user
145     * state they maintain for running users.  This is called prior to sending the SHUTDOWN
146     * broadcast to the user; it is a good place to stop making use of any resources of that
147     * user (such as binding to a service running in the user).
148     * @param userHandle The identifier of the user.
149     */
150    public void onStopUser(int userHandle) {}
151
152    /**
153     * Called when an existing user is stopping, for system services to finalize any per-user
154     * state they maintain for running users.  This is called after all application process
155     * teardown of the user is complete.
156     * @param userHandle The identifier of the user.
157     */
158    public void onCleanupUser(int userHandle) {}
159
160    /**
161     * Publish the service so it is accessible to other services and apps.
162     */
163    protected final void publishBinderService(String name, IBinder service) {
164        publishBinderService(name, service, false);
165    }
166
167    /**
168     * Publish the service so it is accessible to other services and apps.
169     */
170    protected final void publishBinderService(String name, IBinder service,
171            boolean allowIsolated) {
172        ServiceManager.addService(name, service, allowIsolated);
173    }
174
175    /**
176     * Get a binder service by its name.
177     */
178    protected final IBinder getBinderService(String name) {
179        return ServiceManager.getService(name);
180    }
181
182    /**
183     * Publish the service so it is only accessible to the system process.
184     */
185    protected final <T> void publishLocalService(Class<T> type, T service) {
186        LocalServices.addService(type, service);
187    }
188
189    /**
190     * Get a local service by interface.
191     */
192    protected final <T> T getLocalService(Class<T> type) {
193        return LocalServices.getService(type);
194    }
195
196    private SystemServiceManager getManager() {
197        return LocalServices.getService(SystemServiceManager.class);
198    }
199}
200