/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.logging;
import java.lang.reflect.Constructor;
import java.util.Hashtable;
import org.apache.commons.logging.impl.NoOpLog;
/**
* <p>Factory for creating {@link Log} instances. Applications should call
* the <code>makeNewLogInstance()</code> method to instantiate new instances
* of the configured {@link Log} implementation class.</p>
*
* <p>By default, calling <code>getInstance()</code> will use the following
* algorithm:</p>
* <ul>
* <li>If Log4J is available, return an instance of
* <code>org.apache.commons.logging.impl.Log4JLogger</code>.</li>
* <li>If JDK 1.4 or later is available, return an instance of
* <code>org.apache.commons.logging.impl.Jdk14Logger</code>.</li>
* <li>Otherwise, return an instance of
* <code>org.apache.commons.logging.impl.NoOpLog</code>.</li>
* </ul>
*
* <p>You can change the default behavior in one of two ways:</p>
* <ul>
* <li>On the startup command line, set the system property
* <code>org.apache.commons.logging.log</code> to the name of the
* <code>org.apache.commons.logging.Log</code> implementation class
* you want to use.</li>
* <li>At runtime, call <code>LogSource.setLogImplementation()</code>.</li>
* </ul>
*
* @deprecated Use {@link LogFactory} instead - The default factory
* implementation performs exactly the same algorithm as this class did
*
* @author Rod Waldhoff
* @version $Id: LogSource.java 424107 2006-07-20 23:15:42Z skitching $
*/
public class LogSource {
// ------------------------------------------------------- Class Attributes
static protected Hashtable logs = new Hashtable();
/** Is log4j available (in the current classpath) */
static protected boolean log4jIsAvailable = false;
/** Is JDK 1.4 logging available */
static protected boolean jdk14IsAvailable = false;
/** Constructor for current log class */
static protected Constructor logImplctor = null;
// ----------------------------------------------------- Class Initializers
static {
// Is Log4J Available?
try {
if (null != Class.forName("org.apache.log4j.Logger")) {
log4jIsAvailable = true;
} else {
log4jIsAvailable = false;
}
} catch (Throwable t) {
log4jIsAvailable = false;
}
// Is JDK 1.4 Logging Available?
try {
if ((null != Class.forName("java.util.logging.Logger")) &&
(null != Class.forName("org.apache.commons.logging.impl.Jdk14Logger"))) {
jdk14IsAvailable = true;
} else {
jdk14IsAvailable = false;
}
} catch (Throwable t) {
jdk14IsAvailable = false;
}
// Set the default Log implementation
String name = null;
try {
name = System.getProperty("org.apache.commons.logging.log");
if (name == null) {
name = System.getProperty("org.apache.commons.logging.Log");
}
} catch (Throwable t) {
}
if (name != null) {
try {
setLogImplementation(name);
} catch (Throwable t) {
try {
setLogImplementation
("org.apache.commons.logging.impl.NoOpLog");
} catch (Throwable u) {
;
}
}
} else {
try {
if (log4jIsAvailable) {
setLogImplementation
("org.apache.commons.logging.impl.Log4JLogger");
} else if (jdk14IsAvailable) {
setLogImplementation
("org.apache.commons.logging.impl.Jdk14Logger");
} else {
setLogImplementation
("org.apache.commons.logging.impl.NoOpLog");
}
} catch (Throwable t) {
try {
setLogImplementation
("org.apache.commons.logging.impl.NoOpLog");
} catch (Throwable u) {
;
}
}
}
}
// ------------------------------------------------------------ Constructor
/** Don't allow others to create instances */
private LogSource() {
}
// ---------------------------------------------------------- Class Methods
/**
* Set the log implementation/log implementation factory
* by the name of the class. The given class
* must implement {@link Log}, and provide a constructor that
* takes a single {@link String} argument (containing the name
* of the log).
*/
static public void setLogImplementation(String classname) throws
LinkageError, ExceptionInInitializerError,
NoSuchMethodException, SecurityException,
ClassNotFoundException {
try {
Class logclass = Class.forName(classname);
Class[] argtypes = new Class[1];
argtypes[0] = "".getClass();
logImplctor = logclass.getConstructor(argtypes);
} catch (Throwable t) {
logImplctor = null;
}
}
/**
* Set the log implementation/log implementation factory
* by class. The given class must implement {@link Log},
* and provide a constructor that takes a single {@link String}
* argument (containing the name of the log).
*/
static public void setLogImplementation(Class logclass) throws
LinkageError, ExceptionInInitializerError,
NoSuchMethodException, SecurityException {
Class[] argtypes = new Class[1];
argtypes[0] = "".getClass();
logImplctor = logclass.getConstructor(argtypes);
}
/** Get a <code>Log</code> instance by class name */
static public Log getInstance(String name) {
Log log = (Log) (logs.get(name));
if (null == log) {
log = makeNewLogInstance(name);
logs.put(name, log);
}
return log;
}
/** Get a <code>Log</code> instance by class */
static public Log getInstance(Class clazz) {
return getInstance(clazz.getName());
}
/**
* Create a new {@link Log} implementation, based
* on the given <i>name</i>.
* <p>
* The specific {@link Log} implementation returned
* is determined by the value of the
* <tt>org.apache.commons.logging.log</tt> property.
* The value of <tt>org.apache.commons.logging.log</tt> may be set to
* the fully specified name of a class that implements
* the {@link Log} interface. This class must also
* have a public constructor that takes a single
* {@link String} argument (containing the <i>name</i>
* of the {@link Log} to be constructed.
* <p>
* When <tt>org.apache.commons.logging.log</tt> is not set,
* or when no corresponding class can be found,
* this method will return a Log4JLogger
* if the log4j Logger class is
* available in the {@link LogSource}'s classpath, or a
* Jdk14Logger if we are on a JDK 1.4 or later system, or
* NoOpLog if neither of the above conditions is true.
*
* @param name the log name (or category)
*/
static public Log makeNewLogInstance(String name) {
Log log = null;
try {
Object[] args = new Object[1];
args[0] = name;
log = (Log) (logImplctor.newInstance(args));
} catch (Throwable t) {
log = null;
}
if (null == log) {
log = new NoOpLog(name);
}
return log;
}
/**
* Returns a {@link String} array containing the names of
* all logs known to me.
*/
static public String[] getLogNames() {
return (String[]) (logs.keySet().toArray(new String[logs.size()]));
}
}
|