org.apache.commons.logging.impl.LogFactoryImpl Maven / Gradle / Ivy
/* * 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.impl; import java.io.PrintWriter; import java.io.StringWriter; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.net.URL; import java.security.AccessController; import java.security.PrivilegedAction; import java.util.Hashtable; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogConfigurationException; import org.apache.commons.logging.LogFactory; /** * Concrete subclass of {@link LogFactory} that implements the * following algorithm to dynamically select a logging implementation * class to instantiate a wrapper for: *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*
*- Use a factory configuration attribute named *
*org.apache.commons.logging.Logto identify the * requested implementation class.- Use the
*org.apache.commons.logging.Logsystem property * to identify the requested implementation class.- 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.SimpleLog.* If the selected {@link Log} implementation class has a *
setLogFactory()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. ** This factory will remember previously created
Loginstances * for the same name, and will return them on repeated requests to the *getInstance()method. * * @version $Id: LogFactoryImpl.java 1449064 2013-02-22 14:49:22Z tn $ */ 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 (org.apache.commons.logging.Log) 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 (org.apache.commons.logging.Log.allowFlawedContext) * 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 (org.apache.commons.logging.Log.allowFlawedDiscovery) * 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 (
org.apache.commons.logging.Log.allowFlawedHierarchy) * 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
getLogConstructor(), * 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-argumentsetLogFactorymethod of the selected * {@link org.apache.commons.logging.Log} method, if it exists. */ protected Method logMethod = null; /** * The signature of thesetLogFactorymethod 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), * ornullif 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() { return (String[]) attributes.keySet().toArray(new String[attributes.size()]); } /** * Convenience method to derive a name from the specified class and * callgetInstance(String)with it. * * @param clazz Class for which a suitable Log name will be derived * * @exception LogConfigurationException if a suitableLog* instance cannot be returned */ public Log getInstance(Class clazz) throws LogConfigurationException { return getInstance(clazz.getName()); } /** *Construct (if necessary) and return a
* *Loginstance, * using the factory's current set of configuration attributes.NOTE - Depending upon the implementation of * the
* * @param name Logical name of theLogFactoryyou are using, theLog* 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.Loginstance to be * returned (the meaning of this name is only known to the underlying * logging implementation that is being wrapped) * * @exception LogConfigurationException if a suitableLog* 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 anullvalue is equivalent to calling *removeAttribute(name). ** 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 *
* LogFactory.getFactory().setAttribute(...) ** This must be done before the first Log object is created; configuration * changes after that point will be ignored. ** 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
null* 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 = value != null && 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. ** This string will later be prefixed to each "internal logging" message * emitted, so that users can clearly see any unexpected behaviour. *
* 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; } /** *
Return the
* *Constructorthat can be called to instantiate * new {@link org.apache.commons.logging.Log} instances.IMPLEMENTATION NOTE - Race conditions caused by * calling this method from more than one thread are ignored, because * the same
* * @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 JDK 1.3 with Lumberjack 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"); } /** * ReturnConstructorinstance will ultimately be derived * in all circumstances.trueif JDK 1.4 or later logging * is available. Also checks that theThrowableclass * supportsgetStackTrace(), which is required by * Jdk14Logger. * * @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 Log4J 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; 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 lce; } catch (InvocationTargetException e) { // A problem occurred invoking the Constructor or Method // previously discovered Throwable c = e.getTargetException(); throw new LogConfigurationException(c == null ? e : c); } catch (Throwable t) { handleThrowable(t); // may re-throw t // A problem occurred invoking the Constructor or Method // previously discovered throw new LogConfigurationException(t); } } // ------------------------------------------------------ Private Methods /** * Calls LogFactory.directGetContextClassLoader under the control of an * AccessController class. This means that java code running under a * security manager that forbids access to ClassLoaders will still work * if this class is given appropriate privileges, even when the caller * doesn't have such privileges. Without using an AccessController, the * the entire call stack must have the privilege before the call is * allowed. * * @return the context classloader associated with the current thread, * or null if security doesn't allow it. * * @throws LogConfigurationException if there was some weird error while * attempting to get the context classloader. * * @throws SecurityException if the current java security policy doesn't * allow this class to access the context classloader. */ private static ClassLoader getContextClassLoaderInternal() throws LogConfigurationException { return (ClassLoader)AccessController.doPrivileged( new PrivilegedAction() { public Object run() { return LogFactory.directGetContextClassLoader(); } }); } /** * Read the specified system property, using an AccessController so that * the property can be read if JCL has been granted the appropriate * security rights even if the calling code has not. ** Take care not to expose the value returned by this method to the * calling application in any way; otherwise the calling app can use that * info to access data that should not be available to it. */ private static String getSystemProperty(final String key, final String def) throws SecurityException { return (String) AccessController.doPrivileged( new PrivilegedAction() { public Object run() { return System.getProperty(key, def); } }); } /** * Fetch the parent classloader of a specified classloader. *
* If a SecurityException occurs, null is returned. *
* Note that this method is non-static merely so logDiagnostic is available. */ private ClassLoader getParentClassLoader(final ClassLoader cl) { try { return (ClassLoader)AccessController.doPrivileged( new PrivilegedAction() { public Object run() { return cl.getParent(); } }); } catch (SecurityException ex) { logDiagnostic("[SECURITY] Unable to obtain parent classloader"); return null; } } /** * Utility method to check whether a particular logging library is * present and available for use. Note that this does not * 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. *
* 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 { // warning: minor security hole here, in that we potentially read a system // property that the caller cannot, then output it in readable form as a // diagnostic message. However it's only ever JCL-specific properties // involved here, so the harm is truly trivial. String value = getSystemProperty(property, null); 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 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
StringBuffer null*/ 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 = getSystemProperty(LOG_PROPERTY, null); } 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 = getSystemProperty(LOG_PROPERTY_OLD, null); } 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 affectStatetrueif this object's state should * be affected by this method call,falseotherwise. * @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; 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) { handleThrowable(t); // may re-throw 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(); currentCL = getParentClassLoader(currentCL); } if (logAdapterClass != null && affectState) { // We've succeeded, so set instance fields this.logClassName = logAdapterClassName; this.logConstructor = constructor; // Identify thesetLogFactorymethod (if there is one) try { this.logMethod = logAdapterClass.getMethod("setLogFactory", logMethodSignature); logDiagnostic("Found method setLogFactory(LogFactory) in '" + logAdapterClassName + "'"); } catch (Throwable t) { handleThrowable(t); // may re-throw 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. ** 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 and the allowFlawedContext option * has been set then the classloader which loaded this class is returned * instead. *
* 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) { return thisClassLoader; } ClassLoader contextClassLoader = getContextClassLoaderInternal(); 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. *
* @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(); current = getParentClassLoader(current); } // scan c2's ancestors to find c1 current = c2; while (current != null) { if (current == c1) { return c2; } // current = current.getParent(); current = getParentClassLoader(current); } return null; } /** * Generates an internal diagnostic logging of the discovery failure and * then throws a
LogConfigurationExceptionthat wraps * the passedThrowable. * * @param logAdapterClassName is the class name of the Log implementation * that could not be instantiated. Cannot benull. * * @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, // USED? Throwable discoveryFlaw) { if (isDiagnosticsEnabled()) { logDiagnostic("Could not instantiate Log '" + logAdapterClassName + "' -- " + discoveryFlaw.getClass().getName() + ": " + discoveryFlaw.getLocalizedMessage()); if (discoveryFlaw instanceof InvocationTargetException ) { // Ok, the lib is there but while trying to create a real underlying // logger something failed in the underlying lib; display info about // that if possible. InvocationTargetException ite = (InvocationTargetException)discoveryFlaw; Throwable cause = ite.getTargetException(); if (cause != null) { logDiagnostic("... InvocationTargetException: " + cause.getClass().getName() + ": " + cause.getLocalizedMessage()); if (cause instanceof ExceptionInInitializerError) { ExceptionInInitializerError eiie = (ExceptionInInitializerError)cause; Throwable cause2 = eiie.getException(); if (cause2 != null) { final StringWriter sw = new StringWriter(); cause2.printStackTrace(new PrintWriter(sw, true)); logDiagnostic("... ExceptionInInitializerError: " + sw.toString()); } } } } } 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. ** There are two possible reasons why we successfully loaded the * specified log adapter class then failed to cast it to a Log object: *
*
*- the specific class just doesn't implement the Log interface * (user screwed up), or *
- the specified class has bound to a Log class loaded by some other * classloader; Log@classloaderX cannot be cast to Log@classloaderY. *
* 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) { handleThrowable(t); // may re-throw 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()); } } } }