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/*
 * 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;

import java.util.Hashtable;

import org.apache.commons.logging.impl.SLF4JLogFactory;

/**
 * 

* Factory for creating {@link Log} instances, which always delegates to an * instance of {@link SLF4JLogFactory}. * *

* * @author Craig R. McClanahan * @author Costin Manolache * @author Richard A. Sitze * @author Ceki Gülcü */ @SuppressWarnings("rawtypes") public abstract class LogFactory { static String UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J = "http://www.slf4j.org/codes.html#unsupported_operation_in_jcl_over_slf4j"; static LogFactory logFactory = new SLF4JLogFactory(); /** * The name (priority) of the key in the config file used to * specify the priority of that particular config file. The associated value * is a floating-point number; higher values take priority over lower values. * *

* This property is not used but preserved here for compatibility. */ public static final String PRIORITY_KEY = "priority"; /** * The name (use_tccl) of the key in the config file used to * specify whether logging classes should be loaded via the thread context * class loader (TCCL), or not. By default, the TCCL is used. * *

* This property is not used but preserved here for compatibility. */ public static final String TCCL_KEY = "use_tccl"; /** * The name of the property used to identify the LogFactory implementation * class name. *

* This property is not used but preserved here for compatibility. */ public static final String FACTORY_PROPERTY = "org.apache.commons.logging.LogFactory"; /** * The fully qualified class name of the fallback LogFactory * implementation class to use, if no other can be found. * *

* This property is not used but preserved here for compatibility. */ public static final String FACTORY_DEFAULT = "org.apache.commons.logging.impl.SLF4JLogFactory"; /** * The name of the properties file to search for. *

* This property is not used but preserved here for compatibility. */ public static final String FACTORY_PROPERTIES = "commons-logging.properties"; /** * JDK1.3+ * 'Service Provider' specification. *

* This property is not used but preserved here for compatibility. */ protected static final String SERVICE_ID = "META-INF/services/org.apache.commons.logging.LogFactory"; /** * The name (org.apache.commons.logging.diagnostics.dest) of * the property used to enable internal commons-logging diagnostic output, in * order to get information on what logging implementations are being * discovered, what classloaders they are loaded through, etc. * *

* This property is not used but preserved here for compatibility. */ public static final String DIAGNOSTICS_DEST_PROPERTY = "org.apache.commons.logging.diagnostics.dest"; /** *

* Setting this system property value allows the Hashtable used * to store classloaders to be substituted by an alternative implementation. *

* This property is not used but preserved here for compatibility. */ public static final String HASHTABLE_IMPLEMENTATION_PROPERTY = "org.apache.commons.logging.LogFactory.HashtableImpl"; /** * The previously constructed LogFactory instances, keyed by * the ClassLoader with which it was created. * *

* This property is not used but preserved here for compatibility. */ protected static Hashtable factories = null; /** *

* This property is not used but preserved here for compatibility. */ protected static LogFactory nullClassLoaderFactory = null; /** * Protected constructor that is not available for public use. */ protected LogFactory() { } // --------------------------------------------------------- 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 * @return configuration attribute */ public abstract Object getAttribute(String 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. * * @return names of all currently defined configuration attributes */ public abstract String[] getAttributeNames(); /** * 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 abstract Log getInstance(Class clazz) throws LogConfigurationException; /** *

* 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 abstract Log getInstance(String name) throws LogConfigurationException; /** * Release any internal references to previously created {@link 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 abstract void release(); /** * 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 abstract void removeAttribute(String 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 abstract void setAttribute(String name, Object value); // --------------------------------------------------------- Static Methods /** *

* Construct (if necessary) and return a LogFactory instance, * using the following ordered lookup procedure to determine the name of the * implementation class to be loaded. *

*
    *
  • The org.apache.commons.logging.LogFactory system * property.
  • *
  • The JDK 1.3 Service Discovery mechanism
  • *
  • Use the properties file commons-logging.properties * file, if found in the class path of this class. The configuration file is * in standard java.util.Properties format and contains the * fully qualified name of the implementation class with the key being the * system property defined above.
  • *
  • Fall back to a default implementation class ( * org.apache.commons.logging.impl.SLF4FLogFactory).
  • *
* *

* NOTE- If the properties file method of identifying the * LogFactory implementation class is utilized, all of the * properties defined in this file will be set as configuration attributes on * the corresponding LogFactory instance. *

* * @exception LogConfigurationException * if the implementation class is not available or cannot * be instantiated. */ public static LogFactory getFactory() throws LogConfigurationException { return logFactory; } /** * Convenience method to return a named logger, without the application having * to care about factories. * * @param clazz * Class from which a log name will be derived * * @exception LogConfigurationException * if a suitable Log instance cannot be * returned */ public static Log getLog(Class clazz) throws LogConfigurationException { return (getFactory().getInstance(clazz)); } /** * Convenience method to return a named logger, without the application having * to care about factories. * * @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 static Log getLog(String name) throws LogConfigurationException { return (getFactory().getInstance(name)); } /** * Release any internal references to previously created {@link LogFactory} * instances that have been associated with the specified class loader (if * any), after calling the instance method release() on each of * them. * * @param classLoader * ClassLoader for which to release the LogFactory */ public static void release(ClassLoader classLoader) { // since SLF4J based JCL does not make use of classloaders, there is nothing // to do here } /** * Release any internal references to previously created {@link LogFactory} * instances, after calling the instance method release() on * each of them. 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 static void releaseAll() { // since SLF4J based JCL does not make use of classloaders, there is nothing // to do here } /** * Returns a string that uniquely identifies the specified object, including * its class. *

* The returned string is of form "classname@hashcode", i.e. is the same as the * return value of the Object.toString() method, but works even when the * specified object's class has overridden the toString method. * * @param o * may be null. * @return a string of form classname@hashcode, or "null" if param o is null. * @since 1.1 */ public static String objectId(Object o) { if (o == null) { return "null"; } else { return o.getClass().getName() + "@" + System.identityHashCode(o); } } // protected methods which were added in JCL 1.1. These are not used // by SLF4JLogFactory /** * This method exists to ensure signature compatibility. */ protected static Object createFactory(String factoryClass, ClassLoader classLoader) { throw new UnsupportedOperationException("Operation [factoryClass] is not supported in jcl-over-slf4j. See also " + UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J); } /** * This method exists to ensure signature compatibility. */ protected static ClassLoader directGetContextClassLoader() { throw new UnsupportedOperationException("Operation [directGetContextClassLoader] is not supported in jcl-over-slf4j. See also " + UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J); } /** * This method exists to ensure signature compatibility. */ protected static ClassLoader getContextClassLoader() throws LogConfigurationException { throw new UnsupportedOperationException("Operation [getContextClassLoader] is not supported in jcl-over-slf4j. See also " + UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J); } /** * This method exists to ensure signature compatibility. */ protected static ClassLoader getClassLoader(Class clazz) { throw new UnsupportedOperationException("Operation [getClassLoader] is not supported in jcl-over-slf4j. See also " + UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J); } /** * This method exists to ensure signature compatibility. */ protected static boolean isDiagnosticsEnabled() { throw new UnsupportedOperationException("Operation [isDiagnosticsEnabled] is not supported in jcl-over-slf4j. See also " + UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J); } /** * This method exists to ensure signature compatibility. */ protected static void logRawDiagnostic(String msg) { throw new UnsupportedOperationException("Operation [logRawDiagnostic] is not supported in jcl-over-slf4j. See also " + UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J); } /** * This method exists to ensure signature compatibility. */ protected static LogFactory newFactory(final String factoryClass, final ClassLoader classLoader, final ClassLoader contextClassLoader) { throw new UnsupportedOperationException("Operation [logRawDiagnostic] is not supported in jcl-over-slf4j. See also " + UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J); } /** * This method exists to ensure signature compatibility. */ protected static LogFactory newFactory(final String factoryClass, final ClassLoader classLoader) { throw new UnsupportedOperationException("Operation [newFactory] is not supported in jcl-over-slf4j. See also " + UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J); } }





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