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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.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 * * @author Rod Waldhoff * @version $Id: LogSource.java,v 1.21 2004/02/28 21:46:45 craigmcc Exp $ */ 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 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 = 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()])); } }



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