1 /*
2 * Copyright 2008-2013 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 package de.smartics.maven.issues.cache;
17
18 import java.io.File;
19 import java.util.HashMap;
20 import java.util.Map;
21 import java.util.WeakHashMap;
22
23 import org.apache.commons.logging.Log;
24 import org.apache.commons.logging.LogFactory;
25 import org.eclipse.mylyn.tasks.core.data.TaskData;
26
27 /**
28 * Local cache for task data retrieved from the remote Task repository. The
29 * cache is useful for multi project reports where the same tasks will be
30 * retrieved for each sub project. Instead of connecting to the remote
31 * repository the report renderer will try to read the local stored information.
32 * This information is either cached in-memory or on a secondary storage medium
33 * (defaults to an XML file on the file system).
34 *
35 * @author <a href="mailto:robert.reiner@smartics.de">Robert Reiner</a>
36 * @version $Revision:591 $
37 */
38 public class TaskDataCache
39 {
40 // ********************************* Fields *********************************
41
42 // --- constants ------------------------------------------------------------
43
44 /**
45 * Reference to the logger for this class.
46 */
47 private final Log log = LogFactory.getLog(TaskDataCache.class);
48
49 // --- members --------------------------------------------------------------
50
51 /**
52 * The in-memory cache of the {@link TaskData tasks} fetched from the remote
53 * repository.
54 * <p>
55 * The key is the unique identifier of the task, the value the task
56 * information.
57 * </p>
58 */
59 private final Map<String, TaskData> cache;
60
61 /**
62 * The storage handler to make task data instances persistent. The task store
63 * has a value of <code>null</code> if no persistent store is used (i.e.
64 * <code>usePersistentStore</code> is <code>false</code>.
65 */
66 private final TaskDataStore taskStore;
67
68 /**
69 * The flag to indicate whether to use a persistent store (<code>true</code>)
70 * or not (<code>false</code>). If the persistent store is used each task is
71 * stored to the specified path.
72 */
73 private final boolean usePersistentStore;
74
75 // ****************************** Initializer *******************************
76
77 // ****************************** Constructors ******************************
78
79 /**
80 * Convenience constructor to create a cache where all tasks are stored
81 * in-memory.
82 */
83 public TaskDataCache()
84 {
85 this((TaskDataStore) null);
86 }
87
88 /**
89 * Convenience constructor to create a file based task data store to write to
90 * the given location.
91 *
92 * @param persistentStoreDirectory the reference to the directory to store the
93 * individual task files. If this value is <code>null</code> the
94 * tasks will only be stored in-memory with a strong hash map. If
95 * not-<code>null</code>, a weak hash map is used and tasks that are
96 * removed from memory are written to this location.
97 */
98 public TaskDataCache(final String encoding, final File persistentStoreDirectory)
99 {
100 this(persistentStoreDirectory != null ? new XmlTaskDataStore(encoding,
101 persistentStoreDirectory) : null);
102 }
103
104 /**
105 * Default constructor.
106 *
107 * @param taskStore the reference to the task store to store the individual
108 * task data. If this value is <code>null</code> the tasks will only
109 * be stored in-memory with a strong hash map. If not-
110 * <code>null</code>, a weak hash map is used and tasks that are
111 * removed from memory are written to this store.
112 */
113 public TaskDataCache(final TaskDataStore taskStore)
114 {
115 this.usePersistentStore = (taskStore != null);
116 if (usePersistentStore)
117 {
118 this.taskStore = taskStore;
119 cache = new WeakHashMap<String, TaskData>();
120 }
121 else
122 {
123 this.taskStore = null;
124 cache = new HashMap<String, TaskData>();
125 }
126 }
127
128 // ****************************** Inner Classes *****************************
129
130 // ********************************* Methods ********************************
131
132 // --- init -----------------------------------------------------------------
133
134 // --- get&set --------------------------------------------------------------
135
136 // --- business -------------------------------------------------------------
137
138 /**
139 * Returns the task uniquely references by the given identifier.
140 *
141 * @param id the unique identifier of the task.
142 * @return the requested task.
143 */
144 public TaskData getTask(final String id)
145 {
146 TaskData task = cache.get(id);
147 if (task == null && usePersistentStore)
148 {
149 try
150 {
151 task = taskStore.load(id);
152 cache.put(id, task);
153 }
154 catch (final PersistenceException e)
155 {
156 if (log.isDebugEnabled())
157 {
158 log.debug("Cannot load task '" + id + "' from persistency layer.", e);
159 }
160 }
161 }
162 return task;
163 }
164
165 /**
166 * Adds the task to the cache. The task can be retrieved by
167 * {@link #getTask(String)} by passing in the identifier of the task (
168 * {@link TaskData#getTaskId()}).
169 *
170 * @param task the task information to cache.
171 */
172 public void addTask(final TaskData task)
173 {
174 final String id = task.getTaskId();
175 cache.put(id, task);
176 if (usePersistentStore)
177 {
178 try
179 {
180 taskStore.persist(task);
181 }
182 catch (final PersistenceException e)
183 {
184 if (log.isDebugEnabled())
185 {
186 log.debug("Cannot persist task '" + id + "'.", e);
187 }
188 }
189 }
190 }
191
192 // --- object basics --------------------------------------------------------
193
194 }