org.apache.commons.logging.impl.LogFactoryImpl Maven / Gradle / Ivy
/*
* Copyright 2001-2004 The Apache Software Foundation.
*
* Licensed 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.impl;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogConfigurationException;
import org.apache.commons.logging.LogFactory;
/**
* Concrete subclass of {@link LogFactory} that implements the
* following algorithm to dynamically select a logging implementation
* class to instantiate a wrapper for.
*
* - Use a factory configuration attribute named
*
org.apache.commons.logging.Log to identify the
* requested implementation class.
* - Use the
org.apache.commons.logging.Log system property
* to identify the requested implementation class.
* - 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.SimpleLog.
*
*
* If the selected {@link Log} implementation class has a
* setLogFactory() method that accepts a {@link LogFactory}
* parameter, this method will be called on each newly created instance
* to identify the associated factory. This makes factory configuration
* attributes available to the Log instance, if it so desires.
*
* This factory will remember previously created Log instances
* for the same name, and will return them on repeated requests to the
* getInstance() method. This implementation ignores any
* configured attributes.
*
* @author Rod Waldhoff
* @author Craig R. McClanahan
* @author Richard A. Sitze
* @version $Revision: 1.33 $ $Date: 2004/03/06 21:52:59 $
*/
public class LogFactoryImpl extends LogFactory {
// ----------------------------------------------------------- Constructors
/**
* Public no-arguments constructor required by the lookup mechanism.
*/
public LogFactoryImpl() {
super();
}
// ----------------------------------------------------- Manifest Constants
/**
* The name of the system property identifying our {@link Log}
* implementation class.
*/
public static final String LOG_PROPERTY =
"org.apache.commons.logging.Log";
/**
* The deprecated system property used for backwards compatibility with
* the old {@link org.apache.commons.logging.LogSource} class.
*/
protected static final String LOG_PROPERTY_OLD =
"org.apache.commons.logging.log";
/**
* The name of the {@link Log} interface class.
*/
private static final String LOG_INTERFACE =
"org.apache.commons.logging.Log";
// ----------------------------------------------------- Instance Variables
/**
* Configuration attributes.
*/
protected Hashtable attributes = new Hashtable();
/**
* The {@link org.apache.commons.logging.Log} instances that have
* already been created, keyed by logger name.
*/
protected Hashtable instances = new Hashtable();
/**
* Name of the class implementing the Log interface.
*/
private String logClassName;
/**
* The one-argument constructor of the
* {@link org.apache.commons.logging.Log}
* implementation class that will be used to create new instances.
* This value is initialized by getLogConstructor(),
* and then returned repeatedly.
*/
protected Constructor logConstructor = null;
/**
* The signature of the Constructor to be used.
*/
protected Class logConstructorSignature[] =
{ java.lang.String.class };
/**
* The one-argument setLogFactory method of the selected
* {@link org.apache.commons.logging.Log} method, if it exists.
*/
protected Method logMethod = null;
/**
* The signature of the setLogFactory method to be used.
*/
protected Class logMethodSignature[] =
{ LogFactory.class };
// --------------------------------------------------------- Public Methods
/**
* Return the configuration attribute with the specified name (if any),
* or null if there is no such attribute.
*
* @param name Name of the attribute to return
*/
public Object getAttribute(String name) {
return (attributes.get(name));
}
/**
* Return an array containing the names of all currently defined
* configuration attributes. If there are no such attributes, a zero
* length array is returned.
*/
public String[] getAttributeNames() {
Vector names = new Vector();
Enumeration keys = attributes.keys();
while (keys.hasMoreElements()) {
names.addElement((String) keys.nextElement());
}
String results[] = new String[names.size()];
for (int i = 0; i < results.length; i++) {
results[i] = (String) names.elementAt(i);
}
return (results);
}
/**
* Convenience method to derive a name from the specified class and
* call getInstance(String) with it.
*
* @param clazz Class for which a suitable Log name will be derived
*
* @exception LogConfigurationException if a suitable Log
* instance cannot be returned
*/
public Log getInstance(Class clazz) throws LogConfigurationException {
return (getInstance(clazz.getName()));
}
/**
* Construct (if necessary) and return a Log instance,
* using the factory's current set of configuration attributes.
*
* NOTE - Depending upon the implementation of
* the LogFactory you are using, the Log
* instance you are returned may or may not be local to the current
* application, and may or may not be returned again on a subsequent
* call with the same name argument.
*
* @param name Logical name of the Log instance to be
* returned (the meaning of this name is only known to the underlying
* logging implementation that is being wrapped)
*
* @exception LogConfigurationException if a suitable Log
* instance cannot be returned
*/
public Log getInstance(String name) throws LogConfigurationException {
Log instance = (Log) instances.get(name);
if (instance == null) {
instance = newInstance(name);
instances.put(name, instance);
}
return (instance);
}
/**
* Release any internal references to previously created
* {@link org.apache.commons.logging.Log}
* instances returned by this factory. This is useful in environments
* like servlet containers, which implement application reloading by
* throwing away a ClassLoader. Dangling references to objects in that
* class loader would prevent garbage collection.
*/
public void release() {
instances.clear();
}
/**
* Remove any configuration attribute associated with the specified name.
* If there is no such attribute, no action is taken.
*
* @param name Name of the attribute to remove
*/
public void removeAttribute(String name) {
attributes.remove(name);
}
/**
* Set the configuration attribute with the specified name. Calling
* this with a null value is equivalent to calling
* removeAttribute(name).
*
* @param name Name of the attribute to set
* @param value Value of the attribute to set, or null
* to remove any setting for this attribute
*/
public void setAttribute(String name, Object value) {
if (value == null) {
attributes.remove(name);
} else {
attributes.put(name, value);
}
}
// ------------------------------------------------------ Protected Methods
/**
* Return the fully qualified Java classname of the {@link Log}
* implementation we will be using.
*/
protected String getLogClassName() {
// Return the previously identified class name (if any)
if (logClassName != null) {
return logClassName;
}
logClassName = (String) getAttribute(LOG_PROPERTY);
if (logClassName == null) { // @deprecated
logClassName = (String) getAttribute(LOG_PROPERTY_OLD);
}
if (logClassName == null) {
try {
logClassName = System.getProperty(LOG_PROPERTY);
} catch (SecurityException e) {
;
}
}
if (logClassName == null) { // @deprecated
try {
logClassName = System.getProperty(LOG_PROPERTY_OLD);
} catch (SecurityException e) {
;
}
}
if ((logClassName == null) && isLog4JAvailable()) {
logClassName = "org.apache.commons.logging.impl.Log4JLogger";
}
if ((logClassName == null) && isJdk14Available()) {
logClassName = "org.apache.commons.logging.impl.Jdk14Logger";
}
if ((logClassName == null) && isJdk13LumberjackAvailable()) {
logClassName = "org.apache.commons.logging.impl.Jdk13LumberjackLogger";
}
if (logClassName == null) {
logClassName = "org.apache.commons.logging.impl.SimpleLog";
}
return (logClassName);
}
/**
* Return the Constructor that can be called to instantiate
* new {@link org.apache.commons.logging.Log} instances.
*
* IMPLEMENTATION NOTE - Race conditions caused by
* calling this method from more than one thread are ignored, because
* the same Constructor instance will ultimately be derived
* in all circumstances.
*
* @exception LogConfigurationException if a suitable constructor
* cannot be returned
*/
protected Constructor getLogConstructor()
throws LogConfigurationException {
// Return the previously identified Constructor (if any)
if (logConstructor != null) {
return logConstructor;
}
String logClassName = getLogClassName();
// Attempt to load the Log implementation class
Class logClass = null;
Class logInterface = null;
try {
logInterface = this.getClass().getClassLoader().loadClass
(LOG_INTERFACE);
logClass = loadClass(logClassName);
if (logClass == null) {
throw new LogConfigurationException
("No suitable Log implementation for " + logClassName);
}
if (!logInterface.isAssignableFrom(logClass)) {
Class interfaces[] = logClass.getInterfaces();
for (int i = 0; i < interfaces.length; i++) {
if (LOG_INTERFACE.equals(interfaces[i].getName())) {
throw new LogConfigurationException
("Invalid class loader hierarchy. " +
"You have more than one version of '" +
LOG_INTERFACE + "' visible, which is " +
"not allowed.");
}
}
throw new LogConfigurationException
("Class " + logClassName + " does not implement '" +
LOG_INTERFACE + "'.");
}
} catch (Throwable t) {
throw new LogConfigurationException(t);
}
// Identify the setLogFactory method (if there is one)
try {
logMethod = logClass.getMethod("setLogFactory",
logMethodSignature);
} catch (Throwable t) {
logMethod = null;
}
// Identify the corresponding constructor to be used
try {
logConstructor = logClass.getConstructor(logConstructorSignature);
return (logConstructor);
} catch (Throwable t) {
throw new LogConfigurationException
("No suitable Log constructor " +
logConstructorSignature+ " for " + logClassName, t);
}
}
/**
* MUST KEEP THIS METHOD PRIVATE.
*
* Exposing this method outside of
* org.apache.commons.logging.LogFactoryImpl
* will create a security violation:
* This method uses AccessController.doPrivileged().
*
*
* Load a class, try first the thread class loader, and
* if it fails use the loader that loaded this class.
*/
private static Class loadClass( final String name )
throws ClassNotFoundException
{
Object result = AccessController.doPrivileged(
new PrivilegedAction() {
public Object run() {
ClassLoader threadCL = getContextClassLoader();
if (threadCL != null) {
try {
return threadCL.loadClass(name);
} catch( ClassNotFoundException ex ) {
// ignore
}
}
try {
return Class.forName( name );
} catch (ClassNotFoundException e) {
return e;
}
}
});
if (result instanceof Class)
return (Class)result;
throw (ClassNotFoundException)result;
}
/**
* Is JDK 1.3 with Lumberjack logging available?
*/
protected boolean isJdk13LumberjackAvailable() {
try {
loadClass("java.util.logging.Logger");
loadClass("org.apache.commons.logging.impl.Jdk13LumberjackLogger");
return (true);
} catch (Throwable t) {
return (false);
}
}
/**
* Return true if JDK 1.4 or later logging
* is available. Also checks that the Throwable class
* supports getStackTrace(), which is required by
* Jdk14Logger.
*/
protected boolean isJdk14Available() {
try {
loadClass("java.util.logging.Logger");
loadClass("org.apache.commons.logging.impl.Jdk14Logger");
Class throwable = loadClass("java.lang.Throwable");
if (throwable.getDeclaredMethod("getStackTrace", null) == null) {
return (false);
}
return (true);
} catch (Throwable t) {
return (false);
}
}
/**
* Is a Log4J implementation available?
*/
protected boolean isLog4JAvailable() {
try {
loadClass("org.apache.log4j.Logger");
loadClass("org.apache.commons.logging.impl.Log4JLogger");
return (true);
} catch (Throwable t) {
return (false);
}
}
/**
* Create and return a new {@link org.apache.commons.logging.Log}
* instance for the specified name.
*
* @param name Name of the new logger
*
* @exception LogConfigurationException if a new instance cannot
* be created
*/
protected Log newInstance(String name) throws LogConfigurationException {
Log instance = null;
try {
Object params[] = new Object[1];
params[0] = name;
instance = (Log) getLogConstructor().newInstance(params);
if (logMethod != null) {
params[0] = this;
logMethod.invoke(instance, params);
}
return (instance);
} catch (InvocationTargetException e) {
Throwable c = e.getTargetException();
if (c != null) {
throw new LogConfigurationException(c);
} else {
throw new LogConfigurationException(e);
}
} catch (Throwable t) {
throw new LogConfigurationException(t);
}
}
}