[slf4j-dev] svn commit: r197 - slf4j/trunk/src/java/org/apache/commons/logging/impl

ceki at slf4j.org ceki at slf4j.org
Fri Aug 26 15:31:29 CEST 2005


Author: ceki
Date: Fri Aug 26 15:31:27 2005
New Revision: 197

Added:
   slf4j/trunk/src/java/org/apache/commons/logging/impl/LogFactoryImpl.java
Log:
original version from Jakarta

Added: slf4j/trunk/src/java/org/apache/commons/logging/impl/LogFactoryImpl.java
==============================================================================
--- (empty file)
+++ slf4j/trunk/src/java/org/apache/commons/logging/impl/LogFactoryImpl.java	Fri Aug 26 15:31:27 2005
@@ -0,0 +1,549 @@
+/*
+ * 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;
+
+
+/**
+ * <p>Concrete subclass of {@link LogFactory} that implements the
+ * following algorithm to dynamically select a logging implementation
+ * class to instantiate a wrapper for.</p>
+ * <ul>
+ * <li>Use a factory configuration attribute named
+ *     <code>org.apache.commons.logging.Log</code> to identify the
+ *     requested implementation class.</li>
+ * <li>Use the <code>org.apache.commons.logging.Log</code> system property
+ *     to identify the requested implementation class.</li>
+ * <li>If <em>Log4J</em> is available, return an instance of
+ *     <code>org.apache.commons.logging.impl.Log4JLogger</code>.</li>
+ * <li>If <em>JDK 1.4 or later</em> is available, return an instance of
+ *     <code>org.apache.commons.logging.impl.Jdk14Logger</code>.</li>
+ * <li>Otherwise, return an instance of
+ *     <code>org.apache.commons.logging.impl.SimpleLog</code>.</li>
+ * </ul>
+ *
+ * <p>If the selected {@link Log} implementation class has a
+ * <code>setLogFactory()</code> 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.</p>
+ *
+ * <p>This factory will remember previously created <code>Log</code> instances
+ * for the same name, and will return them on repeated requests to the
+ * <code>getInstance()</code> method.  This implementation ignores any
+ * configured attributes.</p>
+ *
+ * @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";
+
+
+    /**
+     * <p>The name of the {@link Log} interface class.</p>
+     */
+    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 <code>getLogConstructor()</code>,
+     * 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 <code>setLogFactory</code> method of the selected
+     * {@link org.apache.commons.logging.Log} method, if it exists.
+     */
+    protected Method logMethod = null;
+
+
+    /**
+     * The signature of the <code>setLogFactory</code> method to be used.
+     */
+    protected Class logMethodSignature[] =
+    { LogFactory.class };
+
+
+    // --------------------------------------------------------- Public Methods
+
+
+    /**
+     * Return the configuration attribute with the specified name (if any),
+     * or <code>null</code> 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 <code>getInstance(String)</code> with it.
+     *
+     * @param clazz Class for which a suitable Log name will be derived
+     *
+     * @exception LogConfigurationException if a suitable <code>Log</code>
+     *  instance cannot be returned
+     */
+    public Log getInstance(Class clazz) throws LogConfigurationException {
+
+        return (getInstance(clazz.getName()));
+
+    }
+
+
+    /**
+     * <p>Construct (if necessary) and return a <code>Log</code> instance,
+     * using the factory's current set of configuration attributes.</p>
+     *
+     * <p><strong>NOTE</strong> - Depending upon the implementation of
+     * the <code>LogFactory</code> you are using, the <code>Log</code>
+     * 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.</p>
+     *
+     * @param name Logical name of the <code>Log</code> 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 <code>Log</code>
+     *  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 <code>null</code> value is equivalent to calling
+     * <code>removeAttribute(name)</code>.
+     *
+     * @param name Name of the attribute to set
+     * @param value Value of the attribute to set, or <code>null</code>
+     *  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);
+
+    }
+
+
+    /**
+     * <p>Return the <code>Constructor</code> that can be called to instantiate
+     * new {@link org.apache.commons.logging.Log} instances.</p>
+     *
+     * <p><strong>IMPLEMENTATION NOTE</strong> - Race conditions caused by
+     * calling this method from more than one thread are ignored, because
+     * the same <code>Constructor</code> instance will ultimately be derived
+     * in all circumstances.</p>
+     *
+     * @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 <code>setLogFactory</code> method (if there is one)
+        try {   // protected Class logMethodSignature[] = { LogFactory.class };
+            logMethod = logClass.getMethod("setLogFactory",
+                                           logMethodSignature);          
+        } catch (Throwable t) {
+            logMethod = null;
+        }
+
+        // Identify the corresponding constructor to be used
+        try {   // protected Class logConstructorSignature[] =    { java.lang.String.class };
+            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.
+     *
+     * <p>Exposing this method outside of
+     * <code>org.apache.commons.logging.LogFactoryImpl</code>
+     * will create a security violation:
+     * This method uses <code>AccessController.doPrivileged()</code>.
+     * </p>
+     *
+     * 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 <em>JDK 1.3 with Lumberjack</em> 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);
+        }
+
+    }
+
+
+    /**
+     * <p>Return <code>true</code> if <em>JDK 1.4 or later</em> logging
+     * is available.  Also checks that the <code>Throwable</code> class
+     * supports <code>getStackTrace()</code>, which is required by
+     * Jdk14Logger.</p>
+     */
+    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 <em>Log4J</em> 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);
+        }
+
+    }
+
+
+}



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