| FilterFactory.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 * Copyright: 2005-2013
18 * The copyright to this program is held by its authors.
19 *
20 */
21 package org.crosswire.jsword.book.filter;
22
23 import java.util.HashMap;
24 import java.util.Locale;
25 import java.util.Map;
26
27 import org.crosswire.common.util.PluginUtil;
28 import org.slf4j.Logger;
29 import org.slf4j.LoggerFactory;
30
31 /**
32 * A simple container for all the known filters.
33 *
34 * @see gnu.lgpl.License The GNU Lesser General Public License for details.
35 * @author Joe Walker
36 */
37 public final class FilterFactory {
38 /**
39 * Prevent instantiation
40 */
41 private FilterFactory() {
42 }
43
44 /**
45 * Find a filter given a lookup string. If lookup is null or the filter is
46 * not found then the default filter will be used.
47 *
48 * @param lookup the lookup string for the filter
49 * @return the matching filter
50 */
51 public static Filter getFilter(String lookup) {
52 Filter reply = filters.get(lookup.toLowerCase(Locale.ENGLISH));
53
54 if (reply == null) {
55 reply = deft;
56 }
57
58 return reply.clone();
59 }
60
61 /**
62 * Find a filter given a lookup string
63 *
64 * @return the default filter
65 */
66 public static Filter getDefaultFilter() {
67 return deft.clone();
68 }
69
70 /**
71 * Add to our list of known filters
72 *
73 * @param name
74 * @param instance
75 */
76 public static void addFilter(String name, Filter instance) {
77 filters.put(name.toLowerCase(Locale.ENGLISH), instance);
78 }
79
80 /**
81 * The lookup table of filters
82 */
83 private static Map<String, Filter> filters = new HashMap<String, Filter>();
84
85 /**
86 * The log stream
87 */
88 private static final Logger log = LoggerFactory.getLogger(FilterFactory.class);
89
90 /**
91 * The lookup table of filters
92 */
93 private static volatile Filter deft;
94
95 /**
96 * Populate the lookup table of filters and the default from the properties
97 * file.
98 */
99 static {
100 Map<String, Class<Filter>> map = PluginUtil.getImplementorsMap(Filter.class);
101
102 // the default value
103 try {
104 Class<Filter> cdeft = map.remove("default");
105 deft = cdeft.newInstance();
106 } catch (InstantiationException e) {
107 log.error("Failed to get default filter, will attempt to use first", e);
108 } catch (IllegalAccessException e) {
109 log.error("Failed to get default filter, will attempt to use first", e);
110 }
111
112 // the lookup table
113 Filter instance = null;
114 for (Map.Entry<String, Class<Filter>> entry : map.entrySet()) {
115 try {
116 Class<Filter> clazz = entry.getValue();
117 instance = clazz.newInstance();
118 addFilter(entry.getKey(), instance);
119 } catch (InstantiationException ex) {
120 log.error("Failed to add filter", ex);
121 } catch (IllegalAccessException ex) {
122 log.error("Failed to add filter", ex);
123 }
124 }
125
126 // if the default didn't work then make a stab at an answer
127 if (deft == null) {
128 deft = instance;
129 }
130 }
131 }
132