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/*
 * 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()]); } }





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