1/*
2 * Copyright (C) 2009 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 */
16package android.accounts;
17
18import java.util.concurrent.TimeUnit;
19import java.io.IOException;
20
21/**
22 * A <tt>AccountManagerFuture</tt> represents the result of an asynchronous
23 * {@link AccountManager} call.  Methods are provided to check if the computation is
24 * complete, to wait for its completion, and to retrieve the result of
25 * the computation.  The result can only be retrieved using method
26 * <tt>get</tt> when the computation has completed, blocking if
27 * necessary until it is ready.  Cancellation is performed by the
28 * <tt>cancel</tt> method.  Additional methods are provided to
29 * determine if the task completed normally or was cancelled. Once a
30 * computation has completed, the computation cannot be cancelled.
31 * If you would like to use a <tt>Future</tt> for the sake
32 * of cancellability but not provide a usable result, you can
33 * declare types of the form <tt>Future&lt;?&gt;</tt> and
34 * return <tt>null</tt> as a result of the underlying task.
35 */
36public interface AccountManagerFuture<V> {
37    /**
38     * Attempts to cancel execution of this task.  This attempt will
39     * fail if the task has already completed, has already been cancelled,
40     * or could not be cancelled for some other reason. If successful,
41     * and this task has not started when <tt>cancel</tt> is called,
42     * this task should never run.  If the task has already started,
43     * then the <tt>mayInterruptIfRunning</tt> parameter determines
44     * whether the thread executing this task should be interrupted in
45     * an attempt to stop the task.
46     *
47     * <p>After this method returns, subsequent calls to {@link #isDone} will
48     * always return <tt>true</tt>.  Subsequent calls to {@link #isCancelled}
49     * will always return <tt>true</tt> if this method returned <tt>true</tt>.
50     *
51     * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this
52     * task should be interrupted; otherwise, in-progress tasks are allowed
53     * to complete
54     * @return <tt>false</tt> if the task could not be cancelled,
55     * typically because it has already completed normally;
56     * <tt>true</tt> otherwise
57     */
58    boolean cancel(boolean mayInterruptIfRunning);
59
60    /**
61     * Returns <tt>true</tt> if this task was cancelled before it completed
62     * normally.
63     *
64     * @return <tt>true</tt> if this task was cancelled before it completed
65     */
66    boolean isCancelled();
67
68    /**
69     * Returns <tt>true</tt> if this task completed.
70     *
71     * Completion may be due to normal termination, an exception, or
72     * cancellation -- in all of these cases, this method will return
73     * <tt>true</tt>.
74     *
75     * @return <tt>true</tt> if this task completed
76     */
77    boolean isDone();
78
79    /**
80     * Accessor for the future result the {@link AccountManagerFuture} represents. This
81     * call will block until the result is available. In order to check if the result is
82     * available without blocking, one may call {@link #isDone()} and  {@link #isCancelled()}.
83     * If the request that generated this result fails or is canceled then an exception
84     * will be thrown rather than the call returning normally.
85     * @return the actual result
86     * @throws android.accounts.OperationCanceledException if the request was canceled for any
87     * reason (including if it is forbidden
88     * by policy to modify an account (of that type))
89     * @throws android.accounts.AuthenticatorException if there was an error communicating with
90     * the authenticator or if the authenticator returned an invalid response
91     * @throws java.io.IOException if the authenticator returned an error response that indicates
92     * that it encountered an IOException while communicating with the authentication server
93     */
94    V getResult() throws OperationCanceledException, IOException, AuthenticatorException;
95
96    /**
97     * Accessor for the future result the {@link AccountManagerFuture} represents. This
98     * call will block until the result is available. In order to check if the result is
99     * available without blocking, one may call {@link #isDone()} and  {@link #isCancelled()}.
100     * If the request that generated this result fails or is canceled then an exception
101     * will be thrown rather than the call returning normally. If a timeout is specified then
102     * the request will automatically be canceled if it does not complete in that amount of time.
103     * @param timeout the maximum time to wait
104     * @param unit the time unit of the timeout argument. This must not be null.
105     * @return the actual result
106     * @throws android.accounts.OperationCanceledException if the request was canceled for any
107     * reason
108     * @throws android.accounts.AuthenticatorException if there was an error communicating with
109     * the authenticator or if the authenticator returned an invalid response
110     * @throws java.io.IOException if the authenticator returned an error response that indicates
111     * that it encountered an IOException while communicating with the authentication server
112     */
113    V getResult(long timeout, TimeUnit unit)
114            throws OperationCanceledException, IOException, AuthenticatorException;
115}