1/*
2 * Copyright 2001-2004 The Apache Software Foundation.
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
17package org.apache.commons.logging.impl;
18
19import org.apache.commons.logging.Log;
20import org.apache.commons.logging.LogConfigurationException;
21import org.apache.commons.logging.LogFactory;
22import org.slf4j.Logger;
23import org.slf4j.LoggerFactory;
24import org.slf4j.spi.LocationAwareLogger;
25
26import java.util.ArrayList;
27import java.util.Enumeration;
28import java.util.Hashtable;
29import java.util.List;
30import java.util.concurrent.ConcurrentHashMap;
31import java.util.concurrent.ConcurrentMap;
32
33/**
34 * <p>
35 * Concrete subclass of {@link LogFactory} which always delegates to the
36 * {@link LoggerFactory org.slf4j.LoggerFactory} class.
37 *
38 * <p>
39 * This factory generates instances of {@link SLF4JLog}. It will remember
40 * previously created instances for the same name, and will return them on
41 * repeated requests to the <code>getInstance()</code> method.
42 *
43 * <p>
44 * This implementation ignores any configured attributes.
45 * </p>
46 *
47 * @author Rod Waldhoff
48 * @author Craig R. McClanahan
49 * @author Richard A. Sitze
50 * @author Ceki G&uuml;lc&uuml;
51 */
52@SuppressWarnings("rawtypes")
53public class SLF4JLogFactory extends LogFactory {
54
55    // ----------------------------------------------------------- Constructors
56
57    /**
58     * The {@link org.apache.commons.logging.Log}instances that have already been
59     * created, keyed by logger name.
60     */
61    ConcurrentMap<String, Log> loggerMap;
62
63    /**
64     * Public no-arguments constructor required by the lookup mechanism.
65     */
66    public SLF4JLogFactory() {
67        loggerMap = new ConcurrentHashMap<String, Log>();
68    }
69
70    // ----------------------------------------------------- Manifest Constants
71
72    /**
73     * The name of the system property identifying our {@link Log}implementation
74     * class.
75     */
76    public static final String LOG_PROPERTY = "org.apache.commons.logging.Log";
77
78    // ----------------------------------------------------- Instance Variables
79
80    /**
81     * Configuration attributes.
82     */
83    protected Hashtable attributes = new Hashtable();
84
85    // --------------------------------------------------------- Public Methods
86
87    /**
88     * Return the configuration attribute with the specified name (if any), or
89     * <code>null</code> if there is no such attribute.
90     *
91     * @param name
92     *          Name of the attribute to return
93     */
94    public Object getAttribute(String name) {
95
96        return (attributes.get(name));
97
98    }
99
100    /**
101     * Return an array containing the names of all currently defined configuration
102     * attributes. If there are no such attributes, a zero length array is
103     * returned.
104     */
105    @SuppressWarnings("unchecked")
106    public String[] getAttributeNames() {
107
108        List<String> names = new ArrayList<String>();
109        Enumeration<String> keys = attributes.keys();
110        while (keys.hasMoreElements()) {
111            names.add((String) keys.nextElement());
112        }
113        String results[] = new String[names.size()];
114        for (int i = 0; i < results.length; i++) {
115            results[i] = (String) names.get(i);
116        }
117        return (results);
118
119    }
120
121    /**
122     * Convenience method to derive a name from the specified class and call
123     * <code>getInstance(String)</code> with it.
124     *
125     * @param clazz
126     *          Class for which a suitable Log name will be derived
127     *
128     * @exception LogConfigurationException
129     *              if a suitable <code>Log</code> instance cannot be returned
130     */
131    public Log getInstance(Class clazz) throws LogConfigurationException {
132        return (getInstance(clazz.getName()));
133    }
134
135    /**
136     * <p>
137     * Construct (if necessary) and return a <code>Log</code> instance, using
138     * the factory's current set of configuration attributes.
139     * </p>
140     *
141     * @param name
142     *          Logical name of the <code>Log</code> instance to be returned
143     *          (the meaning of this name is only known to the underlying logging
144     *          implementation that is being wrapped)
145     *
146     * @exception LogConfigurationException
147     *              if a suitable <code>Log</code> instance cannot be returned
148     */
149    public Log getInstance(String name) throws LogConfigurationException {
150        Log instance = loggerMap.get(name);
151        if (instance != null) {
152            return instance;
153        } else {
154            Log newInstance;
155            Logger slf4jLogger = LoggerFactory.getLogger(name);
156            if (slf4jLogger instanceof LocationAwareLogger) {
157                newInstance = new SLF4JLocationAwareLog((LocationAwareLogger) slf4jLogger);
158            } else {
159                newInstance = new SLF4JLog(slf4jLogger);
160            }
161            Log oldInstance = loggerMap.putIfAbsent(name, newInstance);
162            return oldInstance == null ? newInstance : oldInstance;
163        }
164    }
165
166    /**
167     * Release any internal references to previously created
168     * {@link org.apache.commons.logging.Log}instances returned by this factory.
169     * This is useful in environments like servlet containers, which implement
170     * application reloading by throwing away a ClassLoader. Dangling references
171     * to objects in that class loader would prevent garbage collection.
172     */
173    public void release() {
174        // This method is never called by jcl-over-slf4j classes. However,
175        // in certain deployment scenarios, in particular if jcl-over-slf4j.jar
176        // is
177        // in the the web-app class loader and the official commons-logging.jar is
178        // deployed in some parent class loader (e.g. commons/lib), then it is
179        // possible
180        // for the parent class loader to mask the classes shipping in
181        // jcl-over-slf4j.jar.
182        System.out.println("WARN: The method " + SLF4JLogFactory.class + "#release() was invoked.");
183        System.out.println("WARN: Please see http://www.slf4j.org/codes.html#release for an explanation.");
184        System.out.flush();
185    }
186
187    /**
188     * Remove any configuration attribute associated with the specified name. If
189     * there is no such attribute, no action is taken.
190     *
191     * @param name
192     *          Name of the attribute to remove
193     */
194    public void removeAttribute(String name) {
195        attributes.remove(name);
196    }
197
198    /**
199     * Set the configuration attribute with the specified name. Calling this with
200     * a <code>null</code> value is equivalent to calling
201     * <code>removeAttribute(name)</code>.
202     *
203     * @param name
204     *          Name of the attribute to set
205     * @param value
206     *          Value of the attribute to set, or <code>null</code> to remove
207     *          any setting for this attribute
208     */
209    @SuppressWarnings("unchecked")
210    public void setAttribute(String name, Object value) {
211
212        if (value == null) {
213            attributes.remove(name);
214        } else {
215            attributes.put(name, value);
216        }
217
218    }
219}