1 /*
2 * Copyright 2008-2010 smartics, Kronseder & Reiner GmbH
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
17 package de.smartics.maven.issues.cache;
18
19 import java.io.File;
20 import java.util.HashMap;
21 import java.util.Map;
22 import java.util.WeakHashMap;
23
24 import org.apache.commons.logging.Log;
25 import org.apache.commons.logging.LogFactory;
26 import org.eclipse.mylyn.tasks.core.data.TaskData;
27
28 /**
29 * Local cache for task data retrieved from the remote Task repository. The
30 * cache is useful for multi project reports where the same tasks will be
31 * retrieved for each sub project. Instead of connecting to the remote
32 * repository the report renderer will try to read the local stored information.
33 * This information is either cached in-memory or on a secondary storage medium
34 * (defaults to an XML file on the file system).
35 *
36 * @author <a href="mailto:robert.reiner@smartics.de">Robert Reiner</a>
37 * @version $Revision:591 $
38 */
39 public class TaskDataCache
40 {
41 // ********************************* Fields *********************************
42
43 // --- constants ------------------------------------------------------------
44
45 /**
46 * Reference to the logger for this class.
47 */
48 private final Log log = LogFactory.getLog(TaskDataCache.class);
49
50 // --- members --------------------------------------------------------------
51
52 /**
53 * The in-memory cache of the {@link TaskData tasks} fetched from the remote
54 * repository.
55 * <p>
56 * The key is the unique identifier of the task, the value the task
57 * information.
58 * </p>
59 */
60 private final Map<String, TaskData> cache;
61
62 /**
63 * The storage handler to make task data instances persistent. The task store
64 * has a value of <code>null</code> if no persistent store is used (i.e.
65 * <code>usePersistentStore</code> is <code>false</code>.
66 */
67 private final TaskDataStore taskStore;
68
69 /**
70 * The flag to indicate whether to use a persistent store (<code>true</code>)
71 * or not (<code>false</code>). If the persistent store is used each task is
72 * stored to the specified path.
73 */
74 private final boolean usePersistentStore;
75
76 // ****************************** Initializer *******************************
77
78 // ****************************** Constructors ******************************
79
80 /**
81 * Convenience constructor to create a cache where all tasks are stored
82 * in-memory.
83 */
84 public TaskDataCache()
85 {
86 this((TaskDataStore) null);
87 }
88
89 /**
90 * Convenience constructor to create a file based task data store to write to
91 * the given location.
92 *
93 * @param persistentStoreDirectory the reference to the directory to store the
94 * individual task files. If this value is <code>null</code> the
95 * tasks will only be stored in-memory with a strong hash map. If
96 * not-<code>null</code>, a weak hash map is used and tasks that are
97 * removed from memory are written to this location.
98 */
99 public TaskDataCache(final File persistentStoreDirectory)
100 {
101 this(persistentStoreDirectory != null ? new XmlTaskDataStore(
102 persistentStoreDirectory) : null);
103 }
104
105 /**
106 * Default constructor.
107 *
108 * @param taskStore the reference to the task store to store the individual
109 * task data. If this value is <code>null</code> the tasks will only
110 * be stored in-memory with a strong hash map. If not-
111 * <code>null</code>, a weak hash map is used and tasks that are
112 * removed from memory are written to this store.
113 */
114 public TaskDataCache(final TaskDataStore taskStore)
115 {
116 this.usePersistentStore = (taskStore != null);
117 if (usePersistentStore)
118 {
119 this.taskStore = taskStore;
120 cache = new WeakHashMap<String, TaskData>();
121 }
122 else
123 {
124 this.taskStore = null;
125 cache = new HashMap<String, TaskData>();
126 }
127 }
128
129 // ****************************** Inner Classes *****************************
130
131 // ********************************* Methods ********************************
132
133 // --- init -----------------------------------------------------------------
134
135 // --- get&set --------------------------------------------------------------
136
137 // --- business -------------------------------------------------------------
138
139 /**
140 * Returns the task uniquely references by the given identifier.
141 *
142 * @param id the unique identifier of the task.
143 * @return the requested task.
144 */
145 public TaskData getTask(final String id)
146 {
147 TaskData task = cache.get(id);
148 if (task == null && usePersistentStore)
149 {
150 try
151 {
152 task = taskStore.load(id);
153 cache.put(id, task);
154 }
155 catch (final PersistenceException e)
156 {
157 if (log.isDebugEnabled())
158 {
159 log.debug("Cannot load task '" + id + "' from persistency layer.", e);
160 }
161 }
162 }
163 return task;
164 }
165
166 /**
167 * Adds the task to the cache. The task can be retrieved by
168 * {@link #getTask(String)} by passing in the identifier of the task (
169 * {@link TaskData#getTaskId()}).
170 *
171 * @param task the task information to cache.
172 */
173 public void addTask(final TaskData task)
174 {
175 final String id = task.getTaskId();
176 cache.put(id, task);
177 if (usePersistentStore)
178 {
179 try
180 {
181 taskStore.persist(task);
182 }
183 catch (final PersistenceException e)
184 {
185 if (log.isDebugEnabled())
186 {
187 log.debug("Cannot persist task '" + id + "'.", e);
188 }
189 }
190 }
191 }
192
193 // --- object basics --------------------------------------------------------
194
195 }