Source Code Cross Referenced for Log.java in  » J2EE » Enhydra-Demos » org » enhydra » dm » api » loggers » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » J2EE » Enhydra Demos » org.enhydra.dm.api.loggers 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * 
003:         */
004:
005:        package org.enhydra.dm.api.loggers;
006:
007:        import java.io.InputStream;
008:        import java.io.PrintWriter;
009:        import java.io.StringWriter;
010:        import java.text.DateFormat;
011:        import java.text.MessageFormat;
012:        import java.util.Date;
013:        import java.util.Enumeration;
014:        import java.util.Properties;
015:
016:        /**
017:         * Provides logging utility functionality. A provider can extend this class and is
018:         * specified by the "org.enhydra.dm.util.Log" system property.
019:         */
020:        public abstract class Log {
021:
022:            /**
023:             * Logging threshold indicating everything should be logged.
024:             */
025:            public static final int DEBUG = 0;
026:
027:            /**
028:             * Logging threshold indicating useful information should be logged.
029:             */
030:            public static final int INFORMATION = 1;
031:
032:            /**
033:             * Logging threshold indicating warnings should be logged.
034:             */
035:            public static final int WARNING = 2;
036:
037:            /**
038:             * Logging threshold indicating errors should be logged.
039:             */
040:            public static final int ERROR = 3;
041:
042:            /**
043:             * Logging threshold indicating critical errors should be logged.
044:             */
045:            public static final int CRITICAL = 4;
046:
047:            /**
048:             * Logging threshold indicating nothing should be logged.
049:             */
050:            public static final int NOTHING = Integer.MAX_VALUE;
051:
052:            private static final String RESOURCE = Log.class.getName();
053:
054:            private static Log instance = null;
055:
056:            private static boolean logFailureDetected = false;
057:
058:            private int logThreshold = DEBUG;
059:
060:            /**
061:             * Constructed provided for subclasses.
062:             */
063:            protected Log() {
064:            }
065:
066:            /**
067:             * Returns the current logging threshold.
068:             * 
069:             * @return an <code>int</code> containing the current threshold value.
070:             */
071:            public int getThreshold() {
072:                return getInstance().getLogThreshold();
073:            }
074:
075:            /**
076:             * Sets the current logging threshold.
077:             * 
078:             * @param threshold The new logging threshold value.
079:             */
080:            public void setThreshold(int threshold) {
081:                getInstance().setLogThreshold(threshold);
082:            }
083:
084:            /**
085:             * Logs an object for the specified level.
086:             * 
087:             * @param level The logging level.
088:             * @param arg The argument object. <code>String</code>s will be logged directly;
089:             *           <code>Throwable</code>s will log a stack trace.
090:             */
091:            public void log(int level, Object arg) {
092:                getInstance().doLog(level, arg);
093:            }
094:
095:            /**
096:             * Logs a message with an argument object for the specified level.
097:             * 
098:             * @param level The logging level.
099:             * @param message The message. This can contain format arguments, i.e. "{0}".
100:             * @param arg The argument object. A <code>String</code> will be interpreted as a
101:             *           single format value. A <code>Throwable</code> will use the associated
102:             *           stack trace as the format value. A <code>Object[]</code> will be
103:             *           interpreted as a set of format values (i.e., "{0}", "{1}", etc.).
104:             */
105:            public void log(int level, String message, Object arg) {
106:                getInstance().doLog(level, message, arg);
107:            }
108:
109:            public static void setLogger(Log logger) {
110:                instance = logger;
111:            }
112:
113:            public static Log getInstance() {
114:                if (instance != null)
115:                    return instance;
116:                synchronized (Log.class) {
117:                    Log log = null;
118:                    String instanceClass = null;
119:                    try {
120:                        instanceClass = System.getProperty(Log.class.getName());
121:                        if (instanceClass == null) {
122:                            InputStream resource = Log.class
123:                                    .getResourceAsStream(RESOURCE);
124:                            if (resource == null) {
125:                                resource = ClassLoader
126:                                        .getSystemResourceAsStream(RESOURCE);
127:                            }
128:                            if (resource != null) {
129:                                Properties properties = new Properties();
130:                                properties.load(resource);
131:                                Enumeration propertyNames = properties
132:                                        .propertyNames();
133:                                if (propertyNames.hasMoreElements()) {
134:                                    instanceClass = (String) propertyNames
135:                                            .nextElement();
136:                                }
137:                            }
138:                        }
139:                    } catch (Exception ex) {
140:                    }
141:                    if (instanceClass != null) {
142:                        try {
143:                            log = (Log) Class.forName(instanceClass)
144:                                    .newInstance();
145:                        } catch (Exception ex) {
146:                            log = new DefaultLog();
147:                            log.doLog(NOTHING, "Invalid Log class!");
148:                        }
149:                    }
150:                    if (log == null)
151:                        log = new DefaultLog();
152:                    try {
153:                        String logThreshold = System.getProperty(Log.class
154:                                .getName()
155:                                + ".threshold");
156:                        if (logThreshold != null) {
157:                            try {
158:                                logThreshold = logThreshold.toUpperCase();
159:                                Integer value = (Integer) Log.class.getField(
160:                                        logThreshold).get(null);
161:                                log.setLogThreshold(value.intValue());
162:                            } catch (Exception badConstant) {
163:                                try {
164:                                    log.setLogThreshold(Integer
165:                                            .parseInt(logThreshold));
166:                                } catch (Exception badNumber) {
167:                                    log.setLogThreshold(DEBUG);
168:                                    log.doLog(DEBUG, "Invalid Treshold!");
169:                                }
170:                            }
171:                        }
172:                    } catch (Exception ex) {
173:                    }
174:                    return (instance = log);
175:                }
176:            }
177:
178:            /**
179:             * Returns the current logging threshold.
180:             * 
181:             * @return an <code>int</code> containing the current threshold value.
182:             */
183:            protected int getLogThreshold() {
184:                return logThreshold;
185:            }
186:
187:            private void setLogThreshold(int logThreshold) {
188:                this .logThreshold = logThreshold;
189:            }
190:
191:            private void doLog(int level, Object arg) {
192:                if (level < getLogThreshold() || arg == null)
193:                    return;
194:                if (!(arg instanceof  Throwable)) {
195:                    doLog(level, String.valueOf(arg), (Object[]) null);
196:                    return;
197:                }
198:                Throwable throwable = (Throwable) arg;
199:                String message = throwable.getMessage();
200:                message = (message != null) ? message + ": {0}" : "{0}";
201:                StringWriter sw = new StringWriter();
202:                PrintWriter writer = new PrintWriter(sw);
203:                throwable.printStackTrace(writer);
204:                writer.flush();
205:                doLog(level, message, sw);
206:            }
207:
208:            private void doLog(int level, String message, Object arg) {
209:                if (level < getLogThreshold())
210:                    return;
211:                if (arg instanceof  Object[]) {
212:                    doLog(level, message, (Object[]) arg);
213:                    return;
214:                }
215:                if (!(arg instanceof  Throwable)) {
216:                    doLog(level, message, new Object[] { arg });
217:                    return;
218:                }
219:                Throwable throwable = (Throwable) arg;
220:                if (message == null) {
221:                    if (throwable == null)
222:                        return;
223:                    message = throwable.getMessage();
224:                    message = (message != null) ? message + ": {0}" : "{0}";
225:                }
226:                if (throwable != null) {
227:                    StringWriter sw = new StringWriter();
228:                    PrintWriter writer = new PrintWriter(sw);
229:                    throwable.printStackTrace(writer);
230:                    writer.flush();
231:                    doLog(level, message, new Object[] { sw });
232:                } else {
233:                    doLog(level, message, (Object[]) null);
234:                }
235:            }
236:
237:            private void doLog(int level, String message, Object[] args) {
238:                if (level < getLogThreshold() || message == null)
239:                    return;
240:                if (args != null) {
241:                    try {
242:                        message = MessageFormat.format(message, args);
243:                    } catch (Exception ex) {
244:                    }
245:                }
246:                try {
247:                    synchronized (this ) {
248:                        logMessage(level, message);
249:                    }
250:                } catch (Throwable logFailure) {
251:                    synchronized (Log.class) {
252:                        if (logFailureDetected) {
253:                            throw new IllegalStateException(
254:                                    "Log failure detected!");
255:                        }
256:                        logFailureDetected = true;
257:                        Log log = new DefaultLog();
258:                        log.setLogThreshold(DEBUG);
259:                        log.doLog(DEBUG, "Log feilure");// ?
260:                        instance = log;
261:                    }
262:                }
263:            }
264:
265:            /**
266:             * Logs the specified message at the provided level.
267:             * 
268:             * @param level The logging level.
269:             * @param message The message that is to be logged.
270:             */
271:            protected abstract void logMessage(int level, String message);
272:
273:            private static class DefaultLog extends Log {
274:
275:                protected void logMessage(int level, String message) {
276:                    StringBuffer output = new StringBuffer();
277:                    switch (level) {
278:                    case DEBUG:
279:                        output.append("DEBUG [");
280:                        break;
281:                    case INFORMATION:
282:                        output.append("INFORMATION [");
283:                        break;
284:                    case WARNING:
285:                        output.append("WARNING [");
286:                        break;
287:                    case ERROR:
288:                        output.append("ERROR [");
289:                        break;
290:                    case CRITICAL:
291:                        output.append("CRITICAL [");
292:                        break;
293:                    default:
294:                        output.append("UNKNOWN [");
295:                    }
296:                    DateFormat format = DateFormat.getDateTimeInstance(
297:                            DateFormat.SHORT, DateFormat.SHORT);
298:                    output.append(format.format(new Date())).append("]: ");
299:                    output.append(message);
300:                    System.out.println(output);
301:                }
302:
303:            }
304:
305:        }
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