1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.directory.api.ldap.model.cursor;
21
22
23 /**
24 * A basic ClosureMonitor that simply uses a boolean for state and a cause
25 * exception.
26 *
27 * Note that we consciously chose not to synchronize close() operations with
28 * checks to see if the monitor state is closed because it costs to
29 * synchronize and it's OK for the Cursor not to stop immediately when close()
30 * is called.
31 *
32 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
33 */
34 public class DefaultClosureMonitor implements ClosureMonitor
35 {
36 /** Tells if the monitor is closed or not */
37 private boolean closed;
38
39 /** If we get an exception, the cause is stored in this variable */
40 private Exception cause;
41
42
43 /**
44 * {@inheritDoc}
45 */
46 public final void close()
47 {
48 // state check needed to "try" not to overwrite exception (lack of
49 // synchronization may still allow overwriting but who cares that much
50 if ( !closed )
51 {
52 // not going to sync because who cares if it takes a little longer
53 // to stop but we need to set cause before toggling closed state
54 // or else check for closure can throw null cause
55 cause = CursorClosedException.INSTANCE;
56 closed = true;
57 }
58 }
59
60
61 /**
62 * {@inheritDoc}
63 */
64 public final void close( final String cause )
65 {
66 // state check needed to "try" not to overwrite exception (lack of
67 // synchronization may still allow overwriting but who cares that much
68 if ( !closed )
69 {
70 // not going to sync because who cares if it takes a little longer
71 // to stop but we need to set cause before toggling closed state
72 // or else check for closure can throw null cause
73 this.cause = new CursorClosedException( cause );
74 closed = true;
75 }
76 }
77
78
79 /**
80 * {@inheritDoc}
81 */
82 public final void close( final Exception cause )
83 {
84 // state check needed to "try" not to overwrite exception (lack of
85 // synchronization may still allow overwriting but who cares that much
86 if ( !closed )
87 {
88 // not going to sync because who cares if it takes a little longer
89 // to stop but we need to set cause before toggling closed state
90 // or else check for closure can throw null cause
91 this.cause = cause;
92 closed = true;
93 }
94 }
95
96
97 /**
98 * {@inheritDoc}
99 */
100 public final Exception getCause()
101 {
102 return cause;
103 }
104
105
106 /**
107 * {@inheritDoc}
108 */
109 public final boolean isClosed()
110 {
111 return closed;
112 }
113
114
115 /**
116 * {@inheritDoc}
117 */
118 public void checkNotClosed() throws CursorClosedException
119 {
120 // lack of synchronization may cause pass but eventually it will work
121 if ( closed )
122 {
123 throw new CursorClosedException( cause.getMessage() );
124 }
125 }
126 }