org.apache.commons.logging.LogSource Maven / Gradle / Ivy
/*
* 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;
/**
* Factory for creating {@link Log} instances. Applications should call
* the makeNewLogInstance() method to instantiate new instances
* of the configured {@link Log} implementation class.
*
* By default, calling getInstance() will use the following
* algorithm:
*
* - If Log4J is available, return an instance of
*
org.apache.commons.logging.impl.Log4JLogger.
* - If JDK 1.4 or later is available, return an instance of
*
org.apache.commons.logging.impl.Jdk14Logger.
* - Otherwise, return an instance of
*
org.apache.commons.logging.impl.NoOpLog.
*
*
* You can change the default behavior in one of two ways:
*
* - On the startup command line, set the system property
*
org.apache.commons.logging.log to the name of the
* org.apache.commons.logging.Log implementation class
* you want to use.
* - At runtime, call
LogSource.setLogImplementation().
*
*
* @deprecated Use {@link LogFactory} instead - The default factory
* implementation performs exactly the same algorithm as this class did
*
* @version $Id: LogSource.java 1432675 2013-01-13 17:53:30Z tn $
*/
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 {
log4jIsAvailable = null != Class.forName("org.apache.log4j.Logger");
} catch (Throwable t) {
log4jIsAvailable = false;
}
// Is JDK 1.4 Logging Available?
try {
jdk14IsAvailable = null != Class.forName("java.util.logging.Logger") &&
null != Class.forName("org.apache.commons.logging.impl.Jdk14Logger");
} 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) {
// ignored
}
}
} 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) {
// ignored
}
}
}
}
// ------------------------------------------------------------ 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, 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 Log 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 Log instance by class. */
static public Log getInstance(Class clazz) {
return getInstance(clazz.getName());
}
/**
* Create a new {@link Log} implementation, based on the given name.
*
* The specific {@link Log} implementation returned is determined by the
* value of the org.apache.commons.logging.log property. The value
* of org.apache.commons.logging.log 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 name of the {@link Log} to be constructed.
*
* When org.apache.commons.logging.log 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;
try {
Object[] args = { 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()]);
}
}