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Diffstat (limited to 'src/org/apache/commons/logging/impl/LogFactoryImpl.java')
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diff --git a/src/org/apache/commons/logging/impl/LogFactoryImpl.java b/src/org/apache/commons/logging/impl/LogFactoryImpl.java new file mode 100644 index 0000000..8937b2f --- /dev/null +++ b/src/org/apache/commons/logging/impl/LogFactoryImpl.java @@ -0,0 +1,1400 @@ +/* + * 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.net.URL; +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.</p> + * + * @author Rod Waldhoff + * @author Craig R. McClanahan + * @author Richard A. Sitze + * @author Brian Stansberry + * @version $Revision: 399224 $ $Date: 2006-05-03 10:25:54 +0100 (Wed, 03 May 2006) $ + */ + +public class LogFactoryImpl extends LogFactory { + + + /** Log4JLogger class name */ + private static final String LOGGING_IMPL_LOG4J_LOGGER = "org.apache.commons.logging.impl.Log4JLogger"; + /** Jdk14Logger class name */ + private static final String LOGGING_IMPL_JDK14_LOGGER = "org.apache.commons.logging.impl.Jdk14Logger"; + /** Jdk13LumberjackLogger class name */ + private static final String LOGGING_IMPL_LUMBERJACK_LOGGER = "org.apache.commons.logging.impl.Jdk13LumberjackLogger"; + /** SimpleLog class name */ + private static final String LOGGING_IMPL_SIMPLE_LOGGER = "org.apache.commons.logging.impl.SimpleLog"; + + private static final String PKG_IMPL="org.apache.commons.logging.impl."; + private static final int PKG_LEN = PKG_IMPL.length(); + + // ----------------------------------------------------------- Constructors + + + + /** + * Public no-arguments constructor required by the lookup mechanism. + */ + public LogFactoryImpl() { + super(); + initDiagnostics(); // method on this object + if (isDiagnosticsEnabled()) { + logDiagnostic("Instance created."); + } + } + + + // ----------------------------------------------------- Manifest Constants + + + /** + * The name (<code>org.apache.commons.logging.Log</code>) 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 + * old versions of JCL. + */ + protected static final String LOG_PROPERTY_OLD = + "org.apache.commons.logging.log"; + + /** + * The name (<code>org.apache.commons.logging.Log.allowFlawedContext</code>) + * of the system property which can be set true/false to + * determine system behaviour when a bad context-classloader is encountered. + * When set to false, a LogConfigurationException is thrown if + * LogFactoryImpl is loaded via a child classloader of the TCCL (this + * should never happen in sane systems). + * + * Default behaviour: true (tolerates bad context classloaders) + * + * See also method setAttribute. + */ + public static final String ALLOW_FLAWED_CONTEXT_PROPERTY = + "org.apache.commons.logging.Log.allowFlawedContext"; + + /** + * The name (<code>org.apache.commons.logging.Log.allowFlawedDiscovery</code>) + * of the system property which can be set true/false to + * determine system behaviour when a bad logging adapter class is + * encountered during logging discovery. When set to false, an + * exception will be thrown and the app will fail to start. When set + * to true, discovery will continue (though the user might end up + * with a different logging implementation than they expected). + * + * Default behaviour: true (tolerates bad logging adapters) + * + * See also method setAttribute. + */ + public static final String ALLOW_FLAWED_DISCOVERY_PROPERTY = + "org.apache.commons.logging.Log.allowFlawedDiscovery"; + + /** + * The name (<code>org.apache.commons.logging.Log.allowFlawedHierarchy</code>) + * of the system property which can be set true/false to + * determine system behaviour when a logging adapter class is + * encountered which has bound to the wrong Log class implementation. + * When set to false, an exception will be thrown and the app will fail + * to start. When set to true, discovery will continue (though the user + * might end up with a different logging implementation than they expected). + * + * Default behaviour: true (tolerates bad Log class hierarchy) + * + * See also method setAttribute. + */ + public static final String ALLOW_FLAWED_HIERARCHY_PROPERTY = + "org.apache.commons.logging.Log.allowFlawedHierarchy"; + + + /** + * The names of classes that will be tried (in order) as logging + * adapters. Each class is expected to implement the Log interface, + * and to throw NoClassDefFound or ExceptionInInitializerError when + * loaded if the underlying logging library is not available. Any + * other error indicates that the underlying logging library is available + * but broken/unusable for some reason. + */ + private static final String[] classesToDiscover = { + LOGGING_IMPL_LOG4J_LOGGER, + "org.apache.commons.logging.impl.Jdk14Logger", + "org.apache.commons.logging.impl.Jdk13LumberjackLogger", + "org.apache.commons.logging.impl.SimpleLog" + }; + + + // ----------------------------------------------------- Instance Variables + + /** + * Determines whether logging classes should be loaded using the thread-context + * classloader, or via the classloader that loaded this LogFactoryImpl class. + */ + private boolean useTCCL = true; + + /** + * The string prefixed to every message output by the logDiagnostic method. + */ + private String diagnosticPrefix; + + + /** + * 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 }; + + /** + * See getBaseClassLoader and initConfiguration. + */ + private boolean allowFlawedContext; + + /** + * See handleFlawedDiscovery and initConfiguration. + */ + private boolean allowFlawedDiscovery; + + /** + * See handleFlawedHierarchy and initConfiguration. + */ + private boolean allowFlawedHierarchy; + + // --------------------------------------------------------- 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() { + + logDiagnostic("Releasing all known loggers"); + 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>. + * <p> + * This method can be used to set logging configuration programmatically + * rather than via system properties. It can also be used in code running + * within a container (such as a webapp) to configure behaviour on a + * per-component level instead of globally as system properties would do. + * To use this method instead of a system property, call + * <pre> + * LogFactory.getFactory().setAttribute(...) + * </pre> + * This must be done before the first Log object is created; configuration + * changes after that point will be ignored. + * <p> + * This method is also called automatically if LogFactory detects a + * commons-logging.properties file; every entry in that file is set + * automatically as an attribute here. + * + * @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 (logConstructor != null) { + logDiagnostic("setAttribute: call too late; configuration already performed."); + } + + if (value == null) { + attributes.remove(name); + } else { + attributes.put(name, value); + } + + if (name.equals(TCCL_KEY)) { + useTCCL = Boolean.valueOf(value.toString()).booleanValue(); + } + + } + + + // ------------------------------------------------------ + // Static Methods + // + // These methods only defined as workarounds for a java 1.2 bug; + // theoretically none of these are needed. + // ------------------------------------------------------ + + /** + * Gets the context classloader. + * This method is a workaround for a java 1.2 compiler bug. + * @since 1.1 + */ + protected static ClassLoader getContextClassLoader() throws LogConfigurationException { + return LogFactory.getContextClassLoader(); + } + + + /** + * Workaround for bug in Java1.2; in theory this method is not needed. + * See LogFactory.isDiagnosticsEnabled. + */ + protected static boolean isDiagnosticsEnabled() { + return LogFactory.isDiagnosticsEnabled(); + } + + + /** + * Workaround for bug in Java1.2; in theory this method is not needed. + * See LogFactory.getClassLoader. + * @since 1.1 + */ + protected static ClassLoader getClassLoader(Class clazz) { + return LogFactory.getClassLoader(clazz); + } + + + // ------------------------------------------------------ Protected Methods + + /** + * Calculate and cache a string that uniquely identifies this instance, + * including which classloader the object was loaded from. + * <p> + * This string will later be prefixed to each "internal logging" message + * emitted, so that users can clearly see any unexpected behaviour. + * <p> + * Note that this method does not detect whether internal logging is + * enabled or not, nor where to output stuff if it is; that is all + * handled by the parent LogFactory class. This method just computes + * its own unique prefix for log messages. + */ + private void initDiagnostics() { + // It would be nice to include an identifier of the context classloader + // that this LogFactoryImpl object is responsible for. However that + // isn't possible as that information isn't available. It is possible + // to figure this out by looking at the logging from LogFactory to + // see the context & impl ids from when this object was instantiated, + // in order to link the impl id output as this object's prefix back to + // the context it is intended to manage. + // Note that this prefix should be kept consistent with that + // in LogFactory. + Class clazz = this.getClass(); + ClassLoader classLoader = getClassLoader(clazz); + String classLoaderName; + try { + if (classLoader == null) { + classLoaderName = "BOOTLOADER"; + } else { + classLoaderName = objectId(classLoader); + } + } catch(SecurityException e) { + classLoaderName = "UNKNOWN"; + } + diagnosticPrefix = "[LogFactoryImpl@" + System.identityHashCode(this) + " from " + classLoaderName + "] "; + } + + + /** + * Output a diagnostic message to a user-specified destination (if the + * user has enabled diagnostic logging). + * + * @param msg diagnostic message + * @since 1.1 + */ + protected void logDiagnostic(String msg) { + if (isDiagnosticsEnabled()) { + logRawDiagnostic(diagnosticPrefix + msg); + } + } + + /** + * Return the fully qualified Java classname of the {@link Log} + * implementation we will be using. + * + * @deprecated Never invoked by this class; subclasses should not assume + * it will be. + */ + protected String getLogClassName() { + + if (logClassName == null) { + discoverLogImplementation(getClass().getName()); + } + + 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 + * + * @deprecated Never invoked by this class; subclasses should not assume + * it will be. + */ + protected Constructor getLogConstructor() + throws LogConfigurationException { + + // Return the previously identified Constructor (if any) + if (logConstructor == null) { + discoverLogImplementation(getClass().getName()); + } + + return logConstructor; + } + + + /** + * Is <em>JDK 1.3 with Lumberjack</em> logging available? + * + * @deprecated Never invoked by this class; subclasses should not assume + * it will be. + */ + protected boolean isJdk13LumberjackAvailable() { + return isLogLibraryAvailable( + "Jdk13Lumberjack", + "org.apache.commons.logging.impl.Jdk13LumberjackLogger"); + } + + + /** + * <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> + * + * @deprecated Never invoked by this class; subclasses should not assume + * it will be. + */ + protected boolean isJdk14Available() { + return isLogLibraryAvailable( + "Jdk14", + "org.apache.commons.logging.impl.Jdk14Logger"); + } + + + /** + * Is a <em>Log4J</em> implementation available? + * + * @deprecated Never invoked by this class; subclasses should not assume + * it will be. + */ + protected boolean isLog4JAvailable() { + return isLogLibraryAvailable( + "Log4J", + LOGGING_IMPL_LOG4J_LOGGER); + } + + + /** + * 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 { + if (logConstructor == null) { + instance = discoverLogImplementation(name); + } + else { + Object params[] = { name }; + instance = (Log) logConstructor.newInstance(params); + } + + if (logMethod != null) { + Object params[] = { this }; + logMethod.invoke(instance, params); + } + + return (instance); + + } catch (LogConfigurationException lce) { + + // this type of exception means there was a problem in discovery + // and we've already output diagnostics about the issue, etc.; + // just pass it on + throw (LogConfigurationException) lce; + + } catch (InvocationTargetException e) { + // A problem occurred invoking the Constructor or Method + // previously discovered + Throwable c = e.getTargetException(); + if (c != null) { + throw new LogConfigurationException(c); + } else { + throw new LogConfigurationException(e); + } + } catch (Throwable t) { + // A problem occurred invoking the Constructor or Method + // previously discovered + throw new LogConfigurationException(t); + } + } + + + // ------------------------------------------------------ Private Methods + + /** + * Utility method to check whether a particular logging library is + * present and available for use. Note that this does <i>not</i> + * affect the future behaviour of this class. + */ + private boolean isLogLibraryAvailable(String name, String classname) { + if (isDiagnosticsEnabled()) { + logDiagnostic("Checking for '" + name + "'."); + } + try { + Log log = createLogFromClass( + classname, + this.getClass().getName(), // dummy category + false); + + if (log == null) { + if (isDiagnosticsEnabled()) { + logDiagnostic("Did not find '" + name + "'."); + } + return false; + } else { + if (isDiagnosticsEnabled()) { + logDiagnostic("Found '" + name + "'."); + } + return true; + } + } catch(LogConfigurationException e) { + if (isDiagnosticsEnabled()) { + logDiagnostic("Logging system '" + name + "' is available but not useable."); + } + return false; + } + } + + /** + * Attempt to find an attribute (see method setAttribute) or a + * system property with the provided name and return its value. + * <p> + * The attributes associated with this object are checked before + * system properties in case someone has explicitly called setAttribute, + * or a configuration property has been set in a commons-logging.properties + * file. + * + * @return the value associated with the property, or null. + */ + private String getConfigurationValue(String property) { + if (isDiagnosticsEnabled()) { + logDiagnostic("[ENV] Trying to get configuration for item " + property); + } + + Object valueObj = getAttribute(property); + if (valueObj != null) { + if (isDiagnosticsEnabled()) { + logDiagnostic("[ENV] Found LogFactory attribute [" + valueObj + "] for " + property); + } + return valueObj.toString(); + } + + if (isDiagnosticsEnabled()) { + logDiagnostic("[ENV] No LogFactory attribute found for " + property); + } + + try { + String value = System.getProperty(property); + if (value != null) { + if (isDiagnosticsEnabled()) { + logDiagnostic("[ENV] Found system property [" + value + "] for " + property); + } + return value; + } + + if (isDiagnosticsEnabled()) { + logDiagnostic("[ENV] No system property found for property " + property); + } + } catch (SecurityException e) { + if (isDiagnosticsEnabled()) { + logDiagnostic("[ENV] Security prevented reading system property " + property); + } + } + + if (isDiagnosticsEnabled()) { + logDiagnostic("[ENV] No configuration defined for item " + property); + } + + return null; + } + + /** + * Get the setting for the user-configurable behaviour specified by key. + * If nothing has explicitly been set, then return dflt. + */ + private boolean getBooleanConfiguration(String key, boolean dflt) { + String val = getConfigurationValue(key); + if (val == null) + return dflt; + return Boolean.valueOf(val).booleanValue(); + } + + /** + * Initialize a number of variables that control the behaviour of this + * class and that can be tweaked by the user. This is done when the first + * logger is created, not in the constructor of this class, because we + * need to give the user a chance to call method setAttribute in order to + * configure this object. + */ + private void initConfiguration() { + allowFlawedContext = getBooleanConfiguration(ALLOW_FLAWED_CONTEXT_PROPERTY, true); + allowFlawedDiscovery = getBooleanConfiguration(ALLOW_FLAWED_DISCOVERY_PROPERTY, true); + allowFlawedHierarchy = getBooleanConfiguration(ALLOW_FLAWED_HIERARCHY_PROPERTY, true); + } + + + /** + * Attempts to create a Log instance for the given category name. + * Follows the discovery process described in the class javadoc. + * + * @param logCategory the name of the log category + * + * @throws LogConfigurationException if an error in discovery occurs, + * or if no adapter at all can be instantiated + */ + private Log discoverLogImplementation(String logCategory) + throws LogConfigurationException + { + if (isDiagnosticsEnabled()) { + logDiagnostic("Discovering a Log implementation..."); + } + + initConfiguration(); + + Log result = null; + + // See if the user specified the Log implementation to use + String specifiedLogClassName = findUserSpecifiedLogClassName(); + + if (specifiedLogClassName != null) { + if (isDiagnosticsEnabled()) { + logDiagnostic("Attempting to load user-specified log class '" + + specifiedLogClassName + "'..."); + } + + result = createLogFromClass(specifiedLogClassName, + logCategory, + true); + if (result == null) { + StringBuffer messageBuffer = new StringBuffer("User-specified log class '"); + messageBuffer.append(specifiedLogClassName); + messageBuffer.append("' cannot be found or is not useable."); + + // Mistyping or misspelling names is a common fault. + // Construct a good error message, if we can + if (specifiedLogClassName != null) { + informUponSimilarName(messageBuffer, specifiedLogClassName, LOGGING_IMPL_LOG4J_LOGGER); + informUponSimilarName(messageBuffer, specifiedLogClassName, LOGGING_IMPL_JDK14_LOGGER); + informUponSimilarName(messageBuffer, specifiedLogClassName, LOGGING_IMPL_LUMBERJACK_LOGGER); + informUponSimilarName(messageBuffer, specifiedLogClassName, LOGGING_IMPL_SIMPLE_LOGGER); + } + throw new LogConfigurationException(messageBuffer.toString()); + } + + return result; + } + + // No user specified log; try to discover what's on the classpath + // + // Note that we deliberately loop here over classesToDiscover and + // expect method createLogFromClass to loop over the possible source + // classloaders. The effect is: + // for each discoverable log adapter + // for each possible classloader + // see if it works + // + // It appears reasonable at first glance to do the opposite: + // for each possible classloader + // for each discoverable log adapter + // see if it works + // + // The latter certainly has advantages for user-installable logging + // libraries such as log4j; in a webapp for example this code should + // first check whether the user has provided any of the possible + // logging libraries before looking in the parent classloader. + // Unfortunately, however, Jdk14Logger will always work in jvm>=1.4, + // and SimpleLog will always work in any JVM. So the loop would never + // ever look for logging libraries in the parent classpath. Yet many + // users would expect that putting log4j there would cause it to be + // detected (and this is the historical JCL behaviour). So we go with + // the first approach. A user that has bundled a specific logging lib + // in a webapp should use a commons-logging.properties file or a + // service file in META-INF to force use of that logging lib anyway, + // rather than relying on discovery. + + if (isDiagnosticsEnabled()) { + logDiagnostic( + "No user-specified Log implementation; performing discovery" + + " using the standard supported logging implementations..."); + } + for(int i=0; (i<classesToDiscover.length) && (result == null); ++i) { + result = createLogFromClass(classesToDiscover[i], logCategory, true); + } + + if (result == null) { + throw new LogConfigurationException + ("No suitable Log implementation"); + } + + return result; + } + + + /** + * Appends message if the given name is similar to the candidate. + * @param messageBuffer <code>StringBuffer</code> the message should be appended to, + * not null + * @param name the (trimmed) name to be test against the candidate, not null + * @param candidate the candidate name (not null) + */ + private void informUponSimilarName(final StringBuffer messageBuffer, final String name, + final String candidate) { + if (name.equals(candidate)) { + // Don't suggest a name that is exactly the same as the one the + // user tried... + return; + } + + // If the user provides a name that is in the right package, and gets + // the first 5 characters of the adapter class right (ignoring case), + // then suggest the candidate adapter class name. + if (name.regionMatches(true, 0, candidate, 0, PKG_LEN + 5)) { + messageBuffer.append(" Did you mean '"); + messageBuffer.append(candidate); + messageBuffer.append("'?"); + } + } + + + /** + * Checks system properties and the attribute map for + * a Log implementation specified by the user under the + * property names {@link #LOG_PROPERTY} or {@link #LOG_PROPERTY_OLD}. + * + * @return classname specified by the user, or <code>null</code> + */ + private String findUserSpecifiedLogClassName() + { + if (isDiagnosticsEnabled()) { + logDiagnostic("Trying to get log class from attribute '" + LOG_PROPERTY + "'"); + } + String specifiedClass = (String) getAttribute(LOG_PROPERTY); + + if (specifiedClass == null) { // @deprecated + if (isDiagnosticsEnabled()) { + logDiagnostic("Trying to get log class from attribute '" + + LOG_PROPERTY_OLD + "'"); + } + specifiedClass = (String) getAttribute(LOG_PROPERTY_OLD); + } + + if (specifiedClass == null) { + if (isDiagnosticsEnabled()) { + logDiagnostic("Trying to get log class from system property '" + + LOG_PROPERTY + "'"); + } + try { + specifiedClass = System.getProperty(LOG_PROPERTY); + } catch (SecurityException e) { + if (isDiagnosticsEnabled()) { + logDiagnostic("No access allowed to system property '" + + LOG_PROPERTY + "' - " + e.getMessage()); + } + } + } + + if (specifiedClass == null) { // @deprecated + if (isDiagnosticsEnabled()) { + logDiagnostic("Trying to get log class from system property '" + + LOG_PROPERTY_OLD + "'"); + } + try { + specifiedClass = System.getProperty(LOG_PROPERTY_OLD); + } catch (SecurityException e) { + if (isDiagnosticsEnabled()) { + logDiagnostic("No access allowed to system property '" + + LOG_PROPERTY_OLD + "' - " + e.getMessage()); + } + } + } + + // Remove any whitespace; it's never valid in a classname so its + // presence just means a user mistake. As we know what they meant, + // we may as well strip the spaces. + if (specifiedClass != null) { + specifiedClass = specifiedClass.trim(); + } + + return specifiedClass; + } + + + /** + * Attempts to load the given class, find a suitable constructor, + * and instantiate an instance of Log. + * + * @param logAdapterClassName classname of the Log implementation + * + * @param logCategory argument to pass to the Log implementation's + * constructor + * + * @param affectState <code>true</code> if this object's state should + * be affected by this method call, <code>false</code> otherwise. + * + * @return an instance of the given class, or null if the logging + * library associated with the specified adapter is not available. + * + * @throws LogConfigurationException if there was a serious error with + * configuration and the handleFlawedDiscovery method decided this + * problem was fatal. + */ + private Log createLogFromClass(String logAdapterClassName, + String logCategory, + boolean affectState) + throws LogConfigurationException { + + if (isDiagnosticsEnabled()) { + logDiagnostic("Attempting to instantiate '" + logAdapterClassName + "'"); + } + + Object[] params = { logCategory }; + Log logAdapter = null; + Constructor constructor = null; + + Class logAdapterClass = null; + ClassLoader currentCL = getBaseClassLoader(); + + for(;;) { + // Loop through the classloader hierarchy trying to find + // a viable classloader. + logDiagnostic( + "Trying to load '" + + logAdapterClassName + + "' from classloader " + + objectId(currentCL)); + try { + if (isDiagnosticsEnabled()) { + // Show the location of the first occurrence of the .class file + // in the classpath. This is the location that ClassLoader.loadClass + // will load the class from -- unless the classloader is doing + // something weird. + URL url; + String resourceName = logAdapterClassName.replace('.', '/') + ".class"; + if (currentCL != null) { + url = currentCL.getResource(resourceName ); + } else { + url = ClassLoader.getSystemResource(resourceName + ".class"); + } + + if (url == null) { + logDiagnostic("Class '" + logAdapterClassName + "' [" + resourceName + "] cannot be found."); + } else { + logDiagnostic("Class '" + logAdapterClassName + "' was found at '" + url + "'"); + } + } + + Class c = null; + try { + c = Class.forName(logAdapterClassName, true, currentCL); + } catch (ClassNotFoundException originalClassNotFoundException) { + // The current classloader was unable to find the log adapter + // in this or any ancestor classloader. There's no point in + // trying higher up in the hierarchy in this case.. + String msg = "" + originalClassNotFoundException.getMessage(); + logDiagnostic( + "The log adapter '" + + logAdapterClassName + + "' is not available via classloader " + + objectId(currentCL) + + ": " + + msg.trim()); + try { + // Try the class classloader. + // This may work in cases where the TCCL + // does not contain the code executed or JCL. + // This behaviour indicates that the application + // classloading strategy is not consistent with the + // Java 1.2 classloading guidelines but JCL can + // and so should handle this case. + c = Class.forName(logAdapterClassName); + } catch (ClassNotFoundException secondaryClassNotFoundException) { + // no point continuing: this adapter isn't available + msg = "" + secondaryClassNotFoundException.getMessage(); + logDiagnostic( + "The log adapter '" + + logAdapterClassName + + "' is not available via the LogFactoryImpl class classloader: " + + msg.trim()); + break; + } + } + + constructor = c.getConstructor(logConstructorSignature); + Object o = constructor.newInstance(params); + + // Note that we do this test after trying to create an instance + // [rather than testing Log.class.isAssignableFrom(c)] so that + // we don't complain about Log hierarchy problems when the + // adapter couldn't be instantiated anyway. + if (o instanceof Log) { + logAdapterClass = c; + logAdapter = (Log) o; + break; + } + + // Oops, we have a potential problem here. An adapter class + // has been found and its underlying lib is present too, but + // there are multiple Log interface classes available making it + // impossible to cast to the type the caller wanted. We + // certainly can't use this logger, but we need to know whether + // to keep on discovering or terminate now. + // + // The handleFlawedHierarchy method will throw + // LogConfigurationException if it regards this problem as + // fatal, and just return if not. + handleFlawedHierarchy(currentCL, c); + } catch (NoClassDefFoundError e) { + // We were able to load the adapter but it had references to + // other classes that could not be found. This simply means that + // the underlying logger library is not present in this or any + // ancestor classloader. There's no point in trying higher up + // in the hierarchy in this case.. + String msg = "" + e.getMessage(); + logDiagnostic( + "The log adapter '" + + logAdapterClassName + + "' is missing dependencies when loaded via classloader " + + objectId(currentCL) + + ": " + + msg.trim()); + break; + } catch (ExceptionInInitializerError e) { + // A static initializer block or the initializer code associated + // with a static variable on the log adapter class has thrown + // an exception. + // + // We treat this as meaning the adapter's underlying logging + // library could not be found. + String msg = "" + e.getMessage(); + logDiagnostic( + "The log adapter '" + + logAdapterClassName + + "' is unable to initialize itself when loaded via classloader " + + objectId(currentCL) + + ": " + + msg.trim()); + break; + } catch(LogConfigurationException e) { + // call to handleFlawedHierarchy above must have thrown + // a LogConfigurationException, so just throw it on + throw e; + } catch(Throwable t) { + // handleFlawedDiscovery will determine whether this is a fatal + // problem or not. If it is fatal, then a LogConfigurationException + // will be thrown. + handleFlawedDiscovery(logAdapterClassName, currentCL, t); + } + + if (currentCL == null) { + break; + } + + // try the parent classloader + currentCL = currentCL.getParent(); + } + + if ((logAdapter != null) && affectState) { + // We've succeeded, so set instance fields + this.logClassName = logAdapterClassName; + this.logConstructor = constructor; + + // Identify the <code>setLogFactory</code> method (if there is one) + try { + this.logMethod = logAdapterClass.getMethod("setLogFactory", + logMethodSignature); + logDiagnostic("Found method setLogFactory(LogFactory) in '" + + logAdapterClassName + "'"); + } catch (Throwable t) { + this.logMethod = null; + logDiagnostic( + "[INFO] '" + logAdapterClassName + + "' from classloader " + objectId(currentCL) + + " does not declare optional method " + + "setLogFactory(LogFactory)"); + } + + logDiagnostic( + "Log adapter '" + logAdapterClassName + + "' from classloader " + objectId(logAdapterClass.getClassLoader()) + + " has been selected for use."); + } + + return logAdapter; + } + + + /** + * Return the classloader from which we should try to load the logging + * adapter classes. + * <p> + * This method usually returns the context classloader. However if it + * is discovered that the classloader which loaded this class is a child + * of the context classloader <i>and</i> the allowFlawedContext option + * has been set then the classloader which loaded this class is returned + * instead. + * <p> + * The only time when the classloader which loaded this class is a + * descendant (rather than the same as or an ancestor of the context + * classloader) is when an app has created custom classloaders but + * failed to correctly set the context classloader. This is a bug in + * the calling application; however we provide the option for JCL to + * simply generate a warning rather than fail outright. + * + */ + private ClassLoader getBaseClassLoader() throws LogConfigurationException { + ClassLoader thisClassLoader = getClassLoader(LogFactoryImpl.class); + + if (useTCCL == false) { + return thisClassLoader; + } + + ClassLoader contextClassLoader = getContextClassLoader(); + + ClassLoader baseClassLoader = getLowestClassLoader( + contextClassLoader, thisClassLoader); + + if (baseClassLoader == null) { + // The two classloaders are not part of a parent child relationship. + // In some classloading setups (e.g. JBoss with its + // UnifiedLoaderRepository) this can still work, so if user hasn't + // forbidden it, just return the contextClassLoader. + if (allowFlawedContext) { + if (isDiagnosticsEnabled()) { + logDiagnostic( + "[WARNING] the context classloader is not part of a" + + " parent-child relationship with the classloader that" + + " loaded LogFactoryImpl."); + } + // If contextClassLoader were null, getLowestClassLoader() would + // have returned thisClassLoader. The fact we are here means + // contextClassLoader is not null, so we can just return it. + return contextClassLoader; + } + else { + throw new LogConfigurationException( + "Bad classloader hierarchy; LogFactoryImpl was loaded via" + + " a classloader that is not related to the current context" + + " classloader."); + } + } + + if (baseClassLoader != contextClassLoader) { + // We really should just use the contextClassLoader as the starting + // point for scanning for log adapter classes. However it is expected + // that there are a number of broken systems out there which create + // custom classloaders but fail to set the context classloader so + // we handle those flawed systems anyway. + if (allowFlawedContext) { + if (isDiagnosticsEnabled()) { + logDiagnostic( + "Warning: the context classloader is an ancestor of the" + + " classloader that loaded LogFactoryImpl; it should be" + + " the same or a descendant. The application using" + + " commons-logging should ensure the context classloader" + + " is used correctly."); + } + } else { + throw new LogConfigurationException( + "Bad classloader hierarchy; LogFactoryImpl was loaded via" + + " a classloader that is not related to the current context" + + " classloader."); + } + } + + return baseClassLoader; + } + + /** + * Given two related classloaders, return the one which is a child of + * the other. + * <p> + * @param c1 is a classloader (including the null classloader) + * @param c2 is a classloader (including the null classloader) + * + * @return c1 if it has c2 as an ancestor, c2 if it has c1 as an ancestor, + * and null if neither is an ancestor of the other. + */ + private ClassLoader getLowestClassLoader(ClassLoader c1, ClassLoader c2) { + // TODO: use AccessController when dealing with classloaders here + + if (c1 == null) + return c2; + + if (c2 == null) + return c1; + + ClassLoader current; + + // scan c1's ancestors to find c2 + current = c1; + while (current != null) { + if (current == c2) + return c1; + current = current.getParent(); + } + + // scan c2's ancestors to find c1 + current = c2; + while (current != null) { + if (current == c1) + return c2; + current = current.getParent(); + } + + return null; + } + + /** + * Generates an internal diagnostic logging of the discovery failure and + * then throws a <code>LogConfigurationException</code> that wraps + * the passed <code>Throwable</code>. + * + * @param logAdapterClassName is the class name of the Log implementation + * that could not be instantiated. Cannot be <code>null</code>. + * + * @param classLoader is the classloader that we were trying to load the + * logAdapterClassName from when the exception occurred. + * + * @param discoveryFlaw is the Throwable created by the classloader + * + * @throws LogConfigurationException ALWAYS + */ + private void handleFlawedDiscovery(String logAdapterClassName, + ClassLoader classLoader, + Throwable discoveryFlaw) { + + if (isDiagnosticsEnabled()) { + logDiagnostic("Could not instantiate Log '" + + logAdapterClassName + "' -- " + + discoveryFlaw.getClass().getName() + ": " + + discoveryFlaw.getLocalizedMessage()); + } + + if (!allowFlawedDiscovery) { + throw new LogConfigurationException(discoveryFlaw); + } + } + + + /** + * Report a problem loading the log adapter, then either return + * (if the situation is considered recoverable) or throw a + * LogConfigurationException. + * <p> + * There are two possible reasons why we successfully loaded the + * specified log adapter class then failed to cast it to a Log object: + * <ol> + * <li>the specific class just doesn't implement the Log interface + * (user screwed up), or + * <li> the specified class has bound to a Log class loaded by some other + * classloader; Log@classloaderX cannot be cast to Log@classloaderY. + * </ol> + * <p> + * Here we try to figure out which case has occurred so we can give the + * user some reasonable feedback. + * + * @param badClassLoader is the classloader we loaded the problem class from, + * ie it is equivalent to badClass.getClassLoader(). + * + * @param badClass is a Class object with the desired name, but which + * does not implement Log correctly. + * + * @throws LogConfigurationException when the situation + * should not be recovered from. + */ + private void handleFlawedHierarchy(ClassLoader badClassLoader, Class badClass) + throws LogConfigurationException { + + boolean implementsLog = false; + String logInterfaceName = Log.class.getName(); + Class interfaces[] = badClass.getInterfaces(); + for (int i = 0; i < interfaces.length; i++) { + if (logInterfaceName.equals(interfaces[i].getName())) { + implementsLog = true; + break; + } + } + + if (implementsLog) { + // the class does implement an interface called Log, but + // it is in the wrong classloader + if (isDiagnosticsEnabled()) { + try { + ClassLoader logInterfaceClassLoader = getClassLoader(Log.class); + logDiagnostic( + "Class '" + badClass.getName() + + "' was found in classloader " + + objectId(badClassLoader) + + ". It is bound to a Log interface which is not" + + " the one loaded from classloader " + + objectId(logInterfaceClassLoader)); + } catch (Throwable t) { + logDiagnostic( + "Error while trying to output diagnostics about" + + " bad class '" + badClass + "'"); + } + } + + if (!allowFlawedHierarchy) { + StringBuffer msg = new StringBuffer(); + msg.append("Terminating logging for this context "); + msg.append("due to bad log hierarchy. "); + msg.append("You have more than one version of '"); + msg.append(Log.class.getName()); + msg.append("' visible."); + if (isDiagnosticsEnabled()) { + logDiagnostic(msg.toString()); + } + throw new LogConfigurationException(msg.toString()); + } + + if (isDiagnosticsEnabled()) { + StringBuffer msg = new StringBuffer(); + msg.append("Warning: bad log hierarchy. "); + msg.append("You have more than one version of '"); + msg.append(Log.class.getName()); + msg.append("' visible."); + logDiagnostic(msg.toString()); + } + } else { + // this is just a bad adapter class + if (!allowFlawedDiscovery) { + StringBuffer msg = new StringBuffer(); + msg.append("Terminating logging for this context. "); + msg.append("Log class '"); + msg.append(badClass.getName()); + msg.append("' does not implement the Log interface."); + if (isDiagnosticsEnabled()) { + logDiagnostic(msg.toString()); + } + + throw new LogConfigurationException(msg.toString()); + } + + if (isDiagnosticsEnabled()) { + StringBuffer msg = new StringBuffer(); + msg.append("[WARNING] Log class '"); + msg.append(badClass.getName()); + msg.append("' does not implement the Log interface."); + logDiagnostic(msg.toString()); + } + } + } +} |