| SourceFilterFactory.java |
1 /**
2 * Distribution License:
3 * JSword is free software; you can redistribute it and/or modify it under
4 * the terms of the GNU Lesser General Public License, version 2.1 or later
5 * as published by the Free Software Foundation. This program is distributed
6 * in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
7 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
8 * See the GNU Lesser General Public License for more details.
9 *
10 * The License is available on the internet at:
11 * http://www.gnu.org/copyleft/lgpl.html
12 * or by writing to:
13 * Free Software Foundation, Inc.
14 * 59 Temple Place - Suite 330
15 * Boston, MA 02111-1307, USA
16 *
17 * © CrossWire Bible Society, 2005 - 2016
18 *
19 */
20 package org.crosswire.jsword.book.filter;
21
22 import java.util.HashMap;
23 import java.util.Locale;
24 import java.util.Map;
25
26 import org.crosswire.common.util.PluginUtil;
27 import org.slf4j.Logger;
28 import org.slf4j.LoggerFactory;
29
30 /**
31 * A simple container for all the known SourceFilters.
32 *
33 * @see gnu.lgpl.License The GNU Lesser General Public License for details.
34 * @author Joe Walker
35 */
36 public final class SourceFilterFactory {
37 /**
38 * Prevent instantiation
39 */
40 private SourceFilterFactory() {
41 }
42
43 /**
44 * Find a filter given a lookup string. If lookup is null or the filter is
45 * not found then the default filter will be used.
46 *
47 * @param lookup the lookup string for the filter
48 * @return the matching filter
49 */
50 public static SourceFilter getFilter(String lookup) {
51 SourceFilter reply = filters.get(lookup.toLowerCase(Locale.ENGLISH));
52
53 if (reply == null) {
54 reply = deft;
55 }
56
57 return reply.clone();
58 }
59
60 /**
61 * Find a filter given a lookup string
62 *
63 * @return the default filter
64 */
65 public static SourceFilter getDefaultFilter() {
66 return deft.clone();
67 }
68
69 /**
70 * Add to our list of known filters
71 *
72 * @param name
73 * @param instance
74 */
75 public static void addFilter(String name, SourceFilter instance) {
76 filters.put(name.toLowerCase(Locale.ENGLISH), instance);
77 }
78
79 /**
80 * The lookup table of filters
81 */
82 private static Map<String, SourceFilter> filters = new HashMap<String, SourceFilter>();
83
84 /**
85 * The log stream
86 */
87 private static final Logger log = LoggerFactory.getLogger(SourceFilterFactory.class);
88
89 /**
90 * The lookup table of filters
91 */
92 private static volatile SourceFilter deft;
93
94 /**
95 * Populate the lookup table of filters and the default from the properties
96 * file.
97 */
98 static {
99 Map<String, Class<SourceFilter>> map = PluginUtil.getImplementorsMap(SourceFilter.class);
100
101 // the default value
102 try {
103 Class<SourceFilter> cdeft = map.remove("default");
104 deft = cdeft.newInstance();
105 } catch (InstantiationException e) {
106 log.error("Failed to get default filter, will attempt to use first", e);
107 } catch (IllegalAccessException e) {
108 log.error("Failed to get default filter, will attempt to use first", e);
109 }
110
111 // the lookup table
112 SourceFilter instance = null;
113 for (Map.Entry<String, Class<SourceFilter>> entry : map.entrySet()) {
114 try {
115 Class<SourceFilter> clazz = entry.getValue();
116 instance = clazz.newInstance();
117 addFilter(entry.getKey(), instance);
118 } catch (InstantiationException ex) {
119 log.error("Failed to add filter", ex);
120 } catch (IllegalAccessException ex) {
121 log.error("Failed to add filter", ex);
122 }
123 }
124
125 // if the default didn't work then make a stab at an answer
126 if (deft == null) {
127 deft = instance;
128 }
129 }
130 }
131