| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.commons.logging; |
| |
| import java.io.BufferedReader; |
| import java.io.FileOutputStream; |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.io.InputStreamReader; |
| import java.io.PrintStream; |
| import java.net.URL; |
| import java.net.URLConnection; |
| import java.security.AccessController; |
| import java.security.PrivilegedAction; |
| import java.util.Enumeration; |
| import java.util.Hashtable; |
| import java.util.Properties; |
| |
| /** |
| * Factory for creating {@link Log} instances, with discovery and |
| * configuration features similar to that employed by standard Java APIs |
| * such as JAXP. |
| * <p> |
| * <strong>IMPLEMENTATION NOTE</strong> - This implementation is heavily |
| * based on the SAXParserFactory and DocumentBuilderFactory implementations |
| * (corresponding to the JAXP pluggability APIs) found in Apache Xerces. |
| * |
| * @version $Id$ |
| */ |
| public abstract class LogFactory { |
| // Implementation note re AccessController usage |
| // |
| // It is important to keep code invoked via an AccessController to small |
| // auditable blocks. Such code must carefully evaluate all user input |
| // (parameters, system properties, config file contents, etc). As an |
| // example, a Log implementation should not write to its logfile |
| // with an AccessController anywhere in the call stack, otherwise an |
| // insecure application could configure the log implementation to write |
| // to a protected file using the privileges granted to JCL rather than |
| // to the calling application. |
| // |
| // Under no circumstance should a non-private method return data that is |
| // retrieved via an AccessController. That would allow an insecure app |
| // to invoke that method and obtain data that it is not permitted to have. |
| // |
| // Invoking user-supplied code with an AccessController set is not a major |
| // issue (eg invoking the constructor of the class specified by |
| // HASHTABLE_IMPLEMENTATION_PROPERTY). That class will be in a different |
| // trust domain, and therefore must have permissions to do whatever it |
| // is trying to do regardless of the permissions granted to JCL. There is |
| // a slight issue in that untrusted code may point that environment var |
| // to another trusted library, in which case the code runs if both that |
| // lib and JCL have the necessary permissions even when the untrusted |
| // caller does not. That's a pretty hard route to exploit though. |
| |
| // ----------------------------------------------------- Manifest Constants |
| |
| /** |
| * The name (<code>priority</code>) of the key in the config file used to |
| * specify the priority of that particular config file. The associated value |
| * is a floating-point number; higher values take priority over lower values. |
| */ |
| public static final String PRIORITY_KEY = "priority"; |
| |
| /** |
| * The name (<code>use_tccl</code>) of the key in the config file used |
| * to specify whether logging classes should be loaded via the thread |
| * context class loader (TCCL), or not. By default, the TCCL is used. |
| */ |
| public static final String TCCL_KEY = "use_tccl"; |
| |
| /** |
| * The name (<code>org.apache.commons.logging.LogFactory</code>) of the property |
| * used to identify the LogFactory implementation |
| * class name. This can be used as a system property, or as an entry in a |
| * configuration properties file. |
| */ |
| public static final String FACTORY_PROPERTY = "org.apache.commons.logging.LogFactory"; |
| |
| /** |
| * The fully qualified class name of the fallback <code>LogFactory</code> |
| * implementation class to use, if no other can be found. |
| */ |
| public static final String FACTORY_DEFAULT = "org.apache.commons.logging.impl.LogFactoryImpl"; |
| |
| /** |
| * The name (<code>commons-logging.properties</code>) of the properties file to search for. |
| */ |
| public static final String FACTORY_PROPERTIES = "commons-logging.properties"; |
| |
| /** |
| * JDK1.3+ <a href="http://java.sun.com/j2se/1.3/docs/guide/jar/jar.html#Service%20Provider"> |
| * 'Service Provider' specification</a>. |
| */ |
| protected static final String SERVICE_ID = |
| "META-INF/services/org.apache.commons.logging.LogFactory"; |
| |
| /** |
| * The name (<code>org.apache.commons.logging.diagnostics.dest</code>) |
| * of the property used to enable internal commons-logging |
| * diagnostic output, in order to get information on what logging |
| * implementations are being discovered, what classloaders they |
| * are loaded through, etc. |
| * <p> |
| * If a system property of this name is set then the value is |
| * assumed to be the name of a file. The special strings |
| * STDOUT or STDERR (case-sensitive) indicate output to |
| * System.out and System.err respectively. |
| * <p> |
| * Diagnostic logging should be used only to debug problematic |
| * configurations and should not be set in normal production use. |
| */ |
| public static final String DIAGNOSTICS_DEST_PROPERTY = |
| "org.apache.commons.logging.diagnostics.dest"; |
| |
| /** |
| * When null (the usual case), no diagnostic output will be |
| * generated by LogFactory or LogFactoryImpl. When non-null, |
| * interesting events will be written to the specified object. |
| */ |
| private static PrintStream diagnosticsStream = null; |
| |
| /** |
| * A string that gets prefixed to every message output by the |
| * logDiagnostic method, so that users can clearly see which |
| * LogFactory class is generating the output. |
| */ |
| private static final String diagnosticPrefix; |
| |
| /** |
| * Setting this system property |
| * (<code>org.apache.commons.logging.LogFactory.HashtableImpl</code>) |
| * value allows the <code>Hashtable</code> used to store |
| * classloaders to be substituted by an alternative implementation. |
| * <p> |
| * <strong>Note:</strong> <code>LogFactory</code> will print: |
| * <pre> |
| * [ERROR] LogFactory: Load of custom hashtable failed |
| * </pre> |
| * to system error and then continue using a standard Hashtable. |
| * <p> |
| * <strong>Usage:</strong> Set this property when Java is invoked |
| * and <code>LogFactory</code> will attempt to load a new instance |
| * of the given implementation class. |
| * For example, running the following ant scriplet: |
| * <pre> |
| * <java classname="${test.runner}" fork="yes" failonerror="${test.failonerror}"> |
| * ... |
| * <sysproperty |
| * key="org.apache.commons.logging.LogFactory.HashtableImpl" |
| * value="org.apache.commons.logging.AltHashtable"/> |
| * </java> |
| * </pre> |
| * will mean that <code>LogFactory</code> will load an instance of |
| * <code>org.apache.commons.logging.AltHashtable</code>. |
| * <p> |
| * A typical use case is to allow a custom |
| * Hashtable implementation using weak references to be substituted. |
| * This will allow classloaders to be garbage collected without |
| * the need to release them (on 1.3+ JVMs only, of course ;). |
| */ |
| public static final String HASHTABLE_IMPLEMENTATION_PROPERTY = |
| "org.apache.commons.logging.LogFactory.HashtableImpl"; |
| |
| /** Name used to load the weak hashtable implementation by names. */ |
| private static final String WEAK_HASHTABLE_CLASSNAME = |
| "org.apache.commons.logging.impl.WeakHashtable"; |
| |
| /** |
| * A reference to the classloader that loaded this class. This is the |
| * same as LogFactory.class.getClassLoader(). However computing this |
| * value isn't quite as simple as that, as we potentially need to use |
| * AccessControllers etc. It's more efficient to compute it once and |
| * cache it here. |
| */ |
| private static final ClassLoader thisClassLoader; |
| |
| // ----------------------------------------------------------- Constructors |
| |
| /** |
| * Protected constructor that is not available for public use. |
| */ |
| protected LogFactory() { |
| } |
| |
| // --------------------------------------------------------- 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 abstract Object getAttribute(String 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 abstract String[] getAttributeNames(); |
| |
| /** |
| * 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 |
| * @throws LogConfigurationException if a suitable <code>Log</code> |
| * instance cannot be returned |
| */ |
| public abstract Log getInstance(Class clazz) |
| throws LogConfigurationException; |
| |
| /** |
| * Construct (if necessary) and return a <code>Log</code> instance, |
| * using the factory's current set of configuration attributes. |
| * <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. |
| * |
| * @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) |
| * @throws LogConfigurationException if a suitable <code>Log</code> |
| * instance cannot be returned |
| */ |
| public abstract Log getInstance(String name) |
| throws LogConfigurationException; |
| |
| /** |
| * Release any internal references to previously created {@link 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 abstract void release(); |
| |
| /** |
| * 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 abstract void removeAttribute(String 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 abstract void setAttribute(String name, Object value); |
| |
| // ------------------------------------------------------- Static Variables |
| |
| /** |
| * The previously constructed <code>LogFactory</code> instances, keyed by |
| * the <code>ClassLoader</code> with which it was created. |
| */ |
| protected static Hashtable factories = null; |
| |
| /** |
| * Previously constructed <code>LogFactory</code> instance as in the |
| * <code>factories</code> map, but for the case where |
| * <code>getClassLoader</code> returns <code>null</code>. |
| * This can happen when: |
| * <ul> |
| * <li>using JDK1.1 and the calling code is loaded via the system |
| * classloader (very common)</li> |
| * <li>using JDK1.2+ and the calling code is loaded via the boot |
| * classloader (only likely for embedded systems work).</li> |
| * </ul> |
| * Note that <code>factories</code> is a <i>Hashtable</i> (not a HashMap), |
| * and hashtables don't allow null as a key. |
| * @deprecated since 1.1.2 |
| */ |
| protected static volatile LogFactory nullClassLoaderFactory = null; |
| |
| /** |
| * Create the hashtable which will be used to store a map of |
| * (context-classloader -> logfactory-object). Version 1.2+ of Java |
| * supports "weak references", allowing a custom Hashtable class |
| * to be used which uses only weak references to its keys. Using weak |
| * references can fix memory leaks on webapp unload in some cases (though |
| * not all). Version 1.1 of Java does not support weak references, so we |
| * must dynamically determine which we are using. And just for fun, this |
| * code also supports the ability for a system property to specify an |
| * arbitrary Hashtable implementation name. |
| * <p> |
| * Note that the correct way to ensure no memory leaks occur is to ensure |
| * that LogFactory.release(contextClassLoader) is called whenever a |
| * webapp is undeployed. |
| */ |
| private static final Hashtable createFactoryStore() { |
| Hashtable result = null; |
| String storeImplementationClass; |
| try { |
| storeImplementationClass = getSystemProperty(HASHTABLE_IMPLEMENTATION_PROPERTY, null); |
| } catch (SecurityException ex) { |
| // Permissions don't allow this to be accessed. Default to the "modern" |
| // weak hashtable implementation if it is available. |
| storeImplementationClass = null; |
| } |
| |
| if (storeImplementationClass == null) { |
| storeImplementationClass = WEAK_HASHTABLE_CLASSNAME; |
| } |
| try { |
| Class implementationClass = Class.forName(storeImplementationClass); |
| result = (Hashtable) implementationClass.newInstance(); |
| } catch (Throwable t) { |
| handleThrowable(t); // may re-throw t |
| |
| // ignore |
| if (!WEAK_HASHTABLE_CLASSNAME.equals(storeImplementationClass)) { |
| // if the user's trying to set up a custom implementation, give a clue |
| if (isDiagnosticsEnabled()) { |
| // use internal logging to issue the warning |
| logDiagnostic("[ERROR] LogFactory: Load of custom hashtable failed"); |
| } else { |
| // we *really* want this output, even if diagnostics weren't |
| // explicitly enabled by the user. |
| System.err.println("[ERROR] LogFactory: Load of custom hashtable failed"); |
| } |
| } |
| } |
| if (result == null) { |
| result = new Hashtable(); |
| } |
| return result; |
| } |
| |
| // --------------------------------------------------------- Static Methods |
| |
| /** Utility method to safely trim a string. */ |
| private static String trim(String src) { |
| if (src == null) { |
| return null; |
| } |
| return src.trim(); |
| } |
| |
| /** |
| * Checks whether the supplied Throwable is one that needs to be |
| * re-thrown and ignores all others. |
| * |
| * The following errors are re-thrown: |
| * <ul> |
| * <li>ThreadDeath</li> |
| * <li>VirtualMachineError</li> |
| * </ul> |
| * |
| * @param t the Throwable to check |
| */ |
| protected static void handleThrowable(Throwable t) { |
| if (t instanceof ThreadDeath) { |
| throw (ThreadDeath) t; |
| } |
| if (t instanceof VirtualMachineError) { |
| throw (VirtualMachineError) t; |
| } |
| // All other instances of Throwable will be silently ignored |
| } |
| |
| /** |
| * Construct (if necessary) and return a <code>LogFactory</code> |
| * instance, using the following ordered lookup procedure to determine |
| * the name of the implementation class to be loaded. |
| * <p> |
| * <ul> |
| * <li>The <code>org.apache.commons.logging.LogFactory</code> system |
| * property.</li> |
| * <li>The JDK 1.3 Service Discovery mechanism</li> |
| * <li>Use the properties file <code>commons-logging.properties</code> |
| * file, if found in the class path of this class. The configuration |
| * file is in standard <code>java.util.Properties</code> format and |
| * contains the fully qualified name of the implementation class |
| * with the key being the system property defined above.</li> |
| * <li>Fall back to a default implementation class |
| * (<code>org.apache.commons.logging.impl.LogFactoryImpl</code>).</li> |
| * </ul> |
| * <p> |
| * <em>NOTE</em> - If the properties file method of identifying the |
| * <code>LogFactory</code> implementation class is utilized, all of the |
| * properties defined in this file will be set as configuration attributes |
| * on the corresponding <code>LogFactory</code> instance. |
| * <p> |
| * <em>NOTE</em> - In a multi-threaded environment it is possible |
| * that two different instances will be returned for the same |
| * classloader environment. |
| * |
| * @throws LogConfigurationException if the implementation class is not |
| * available or cannot be instantiated. |
| */ |
| public static LogFactory getFactory() throws LogConfigurationException { |
| // Identify the class loader we will be using |
| ClassLoader contextClassLoader = getContextClassLoaderInternal(); |
| |
| if (contextClassLoader == null) { |
| // This is an odd enough situation to report about. This |
| // output will be a nuisance on JDK1.1, as the system |
| // classloader is null in that environment. |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Context classloader is null."); |
| } |
| } |
| |
| // Return any previously registered factory for this class loader |
| LogFactory factory = getCachedFactory(contextClassLoader); |
| if (factory != null) { |
| return factory; |
| } |
| |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic( |
| "[LOOKUP] LogFactory implementation requested for the first time for context classloader " + |
| objectId(contextClassLoader)); |
| logHierarchy("[LOOKUP] ", contextClassLoader); |
| } |
| |
| // Load properties file. |
| // |
| // If the properties file exists, then its contents are used as |
| // "attributes" on the LogFactory implementation class. One particular |
| // property may also control which LogFactory concrete subclass is |
| // used, but only if other discovery mechanisms fail.. |
| // |
| // As the properties file (if it exists) will be used one way or |
| // another in the end we may as well look for it first. |
| |
| Properties props = getConfigurationFile(contextClassLoader, FACTORY_PROPERTIES); |
| |
| // Determine whether we will be using the thread context class loader to |
| // load logging classes or not by checking the loaded properties file (if any). |
| ClassLoader baseClassLoader = contextClassLoader; |
| if (props != null) { |
| String useTCCLStr = props.getProperty(TCCL_KEY); |
| if (useTCCLStr != null) { |
| // The Boolean.valueOf(useTCCLStr).booleanValue() formulation |
| // is required for Java 1.2 compatibility. |
| if (Boolean.valueOf(useTCCLStr).booleanValue() == false) { |
| // Don't use current context classloader when locating any |
| // LogFactory or Log classes, just use the class that loaded |
| // this abstract class. When this class is deployed in a shared |
| // classpath of a container, it means webapps cannot deploy their |
| // own logging implementations. It also means that it is up to the |
| // implementation whether to load library-specific config files |
| // from the TCCL or not. |
| baseClassLoader = thisClassLoader; |
| } |
| } |
| } |
| |
| // Determine which concrete LogFactory subclass to use. |
| // First, try a global system property |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] Looking for system property [" + FACTORY_PROPERTY + |
| "] to define the LogFactory subclass to use..."); |
| } |
| |
| try { |
| String factoryClass = getSystemProperty(FACTORY_PROPERTY, null); |
| if (factoryClass != null) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] Creating an instance of LogFactory class '" + factoryClass + |
| "' as specified by system property " + FACTORY_PROPERTY); |
| } |
| factory = newFactory(factoryClass, baseClassLoader, contextClassLoader); |
| } else { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] No system property [" + FACTORY_PROPERTY + "] defined."); |
| } |
| } |
| } catch (SecurityException e) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] A security exception occurred while trying to create an" + |
| " instance of the custom factory class" + ": [" + trim(e.getMessage()) + |
| "]. Trying alternative implementations..."); |
| } |
| // ignore |
| } catch (RuntimeException e) { |
| // This is not consistent with the behavior when a bad LogFactory class is |
| // specified in a services file. |
| // |
| // One possible exception that can occur here is a ClassCastException when |
| // the specified class wasn't castable to this LogFactory type. |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] An exception occurred while trying to create an" + |
| " instance of the custom factory class" + ": [" + |
| trim(e.getMessage()) + |
| "] as specified by a system property."); |
| } |
| throw e; |
| } |
| |
| // Second, try to find a service by using the JDK1.3 class |
| // discovery mechanism, which involves putting a file with the name |
| // of an interface class in the META-INF/services directory, where the |
| // contents of the file is a single line specifying a concrete class |
| // that implements the desired interface. |
| |
| if (factory == null) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] Looking for a resource file of name [" + SERVICE_ID + |
| "] to define the LogFactory subclass to use..."); |
| } |
| try { |
| final InputStream is = getResourceAsStream(contextClassLoader, SERVICE_ID); |
| |
| if( is != null ) { |
| // This code is needed by EBCDIC and other strange systems. |
| // It's a fix for bugs reported in xerces |
| BufferedReader rd; |
| try { |
| rd = new BufferedReader(new InputStreamReader(is, "UTF-8")); |
| } catch (java.io.UnsupportedEncodingException e) { |
| rd = new BufferedReader(new InputStreamReader(is)); |
| } |
| |
| String factoryClassName; |
| try { |
| factoryClassName = rd.readLine(); |
| } finally { |
| rd.close(); |
| } |
| |
| if (factoryClassName != null && ! "".equals(factoryClassName)) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] Creating an instance of LogFactory class " + |
| factoryClassName + |
| " as specified by file '" + SERVICE_ID + |
| "' which was present in the path of the context classloader."); |
| } |
| factory = newFactory(factoryClassName, baseClassLoader, contextClassLoader ); |
| } |
| } else { |
| // is == null |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] No resource file with name '" + SERVICE_ID + "' found."); |
| } |
| } |
| } catch (Exception ex) { |
| // note: if the specified LogFactory class wasn't compatible with LogFactory |
| // for some reason, a ClassCastException will be caught here, and attempts will |
| // continue to find a compatible class. |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic( |
| "[LOOKUP] A security exception occurred while trying to create an" + |
| " instance of the custom factory class" + |
| ": [" + trim(ex.getMessage()) + |
| "]. Trying alternative implementations..."); |
| } |
| // ignore |
| } |
| } |
| |
| // Third try looking into the properties file read earlier (if found) |
| |
| if (factory == null) { |
| if (props != null) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic( |
| "[LOOKUP] Looking in properties file for entry with key '" + FACTORY_PROPERTY + |
| "' to define the LogFactory subclass to use..."); |
| } |
| String factoryClass = props.getProperty(FACTORY_PROPERTY); |
| if (factoryClass != null) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic( |
| "[LOOKUP] Properties file specifies LogFactory subclass '" + factoryClass + "'"); |
| } |
| factory = newFactory(factoryClass, baseClassLoader, contextClassLoader); |
| |
| // TODO: think about whether we need to handle exceptions from newFactory |
| } else { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] Properties file has no entry specifying LogFactory subclass."); |
| } |
| } |
| } else { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] No properties file available to determine" + " LogFactory subclass from.."); |
| } |
| } |
| } |
| |
| // Fourth, try the fallback implementation class |
| |
| if (factory == null) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic( |
| "[LOOKUP] Loading the default LogFactory implementation '" + FACTORY_DEFAULT + |
| "' via the same classloader that loaded this LogFactory" + |
| " class (ie not looking in the context classloader)."); |
| } |
| |
| // Note: unlike the above code which can try to load custom LogFactory |
| // implementations via the TCCL, we don't try to load the default LogFactory |
| // implementation via the context classloader because: |
| // * that can cause problems (see comments in newFactory method) |
| // * no-one should be customising the code of the default class |
| // Yes, we do give up the ability for the child to ship a newer |
| // version of the LogFactoryImpl class and have it used dynamically |
| // by an old LogFactory class in the parent, but that isn't |
| // necessarily a good idea anyway. |
| factory = newFactory(FACTORY_DEFAULT, thisClassLoader, contextClassLoader); |
| } |
| |
| if (factory != null) { |
| /** |
| * Always cache using context class loader. |
| */ |
| cacheFactory(contextClassLoader, factory); |
| |
| if (props != null) { |
| Enumeration names = props.propertyNames(); |
| while (names.hasMoreElements()) { |
| String name = (String) names.nextElement(); |
| String value = props.getProperty(name); |
| factory.setAttribute(name, value); |
| } |
| } |
| } |
| |
| return factory; |
| } |
| |
| /** |
| * Convenience method to return a named logger, without the application |
| * having to care about factories. |
| * |
| * @param clazz Class from which a log name will be derived |
| * @throws LogConfigurationException if a suitable <code>Log</code> |
| * instance cannot be returned |
| */ |
| public static Log getLog(Class clazz) throws LogConfigurationException { |
| return getFactory().getInstance(clazz); |
| } |
| |
| /** |
| * Convenience method to return a named logger, without the application |
| * having to care about factories. |
| * |
| * @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) |
| * @throws LogConfigurationException if a suitable <code>Log</code> |
| * instance cannot be returned |
| */ |
| public static Log getLog(String name) throws LogConfigurationException { |
| return getFactory().getInstance(name); |
| } |
| |
| /** |
| * Release any internal references to previously created {@link LogFactory} |
| * instances that have been associated with the specified class loader |
| * (if any), after calling the instance method <code>release()</code> on |
| * each of them. |
| * |
| * @param classLoader ClassLoader for which to release the LogFactory |
| */ |
| public static void release(ClassLoader classLoader) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Releasing factory for classloader " + objectId(classLoader)); |
| } |
| // factories is not final and could be replaced in this block. |
| final Hashtable factories = LogFactory.factories; |
| synchronized (factories) { |
| if (classLoader == null) { |
| if (nullClassLoaderFactory != null) { |
| nullClassLoaderFactory.release(); |
| nullClassLoaderFactory = null; |
| } |
| } else { |
| final LogFactory factory = (LogFactory) factories.get(classLoader); |
| if (factory != null) { |
| factory.release(); |
| factories.remove(classLoader); |
| } |
| } |
| } |
| } |
| |
| /** |
| * Release any internal references to previously created {@link LogFactory} |
| * instances, after calling the instance method <code>release()</code> on |
| * each of them. 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 static void releaseAll() { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Releasing factory for all classloaders."); |
| } |
| // factories is not final and could be replaced in this block. |
| final Hashtable factories = LogFactory.factories; |
| synchronized (factories) { |
| final Enumeration elements = factories.elements(); |
| while (elements.hasMoreElements()) { |
| LogFactory element = (LogFactory) elements.nextElement(); |
| element.release(); |
| } |
| factories.clear(); |
| |
| if (nullClassLoaderFactory != null) { |
| nullClassLoaderFactory.release(); |
| nullClassLoaderFactory = null; |
| } |
| } |
| } |
| |
| // ------------------------------------------------------ Protected Methods |
| |
| /** |
| * Safely get access to the classloader for the specified class. |
| * <p> |
| * Theoretically, calling getClassLoader can throw a security exception, |
| * and so should be done under an AccessController in order to provide |
| * maximum flexibility. However in practice people don't appear to use |
| * security policies that forbid getClassLoader calls. So for the moment |
| * all code is written to call this method rather than Class.getClassLoader, |
| * so that we could put AccessController stuff in this method without any |
| * disruption later if we need to. |
| * <p> |
| * Even when using an AccessController, however, this method can still |
| * throw SecurityException. Commons-logging basically relies on the |
| * ability to access classloaders, ie a policy that forbids all |
| * classloader access will also prevent commons-logging from working: |
| * currently this method will throw an exception preventing the entire app |
| * from starting up. Maybe it would be good to detect this situation and |
| * just disable all commons-logging? Not high priority though - as stated |
| * above, security policies that prevent classloader access aren't common. |
| * <p> |
| * Note that returning an object fetched via an AccessController would |
| * technically be a security flaw anyway; untrusted code that has access |
| * to a trusted JCL library could use it to fetch the classloader for |
| * a class even when forbidden to do so directly. |
| * |
| * @since 1.1 |
| */ |
| protected static ClassLoader getClassLoader(Class clazz) { |
| try { |
| return clazz.getClassLoader(); |
| } catch (SecurityException ex) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Unable to get classloader for class '" + clazz + |
| "' due to security restrictions - " + ex.getMessage()); |
| } |
| throw ex; |
| } |
| } |
| |
| /** |
| * Returns the current context classloader. |
| * <p> |
| * In versions prior to 1.1, this method did not use an AccessController. |
| * In version 1.1, an AccessController wrapper was incorrectly added to |
| * this method, causing a minor security flaw. |
| * <p> |
| * In version 1.1.1 this change was reverted; this method no longer uses |
| * an AccessController. User code wishing to obtain the context classloader |
| * must invoke this method via AccessController.doPrivileged if it needs |
| * support for that. |
| * |
| * @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. |
| */ |
| protected static ClassLoader getContextClassLoader() throws LogConfigurationException { |
| return directGetContextClassLoader(); |
| } |
| |
| /** |
| * 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. |
| */ |
| private static ClassLoader getContextClassLoaderInternal() throws LogConfigurationException { |
| return (ClassLoader)AccessController.doPrivileged( |
| new PrivilegedAction() { |
| public Object run() { |
| return directGetContextClassLoader(); |
| } |
| }); |
| } |
| |
| /** |
| * Return the thread context class loader if available; otherwise return null. |
| * <p> |
| * Most/all code should call getContextClassLoaderInternal rather than |
| * calling this method directly. |
| * <p> |
| * The thread context class loader is available for JDK 1.2 |
| * or later, if certain security conditions are met. |
| * <p> |
| * Note that no internal logging is done within this method because |
| * this method is called every time LogFactory.getLogger() is called, |
| * and we don't want too much output generated here. |
| * |
| * @throws LogConfigurationException if a suitable class loader |
| * cannot be identified. |
| * @return the thread's context classloader or {@code null} if the java security |
| * policy forbids access to the context classloader from one of the classes |
| * in the current call stack. |
| * @since 1.1 |
| */ |
| protected static ClassLoader directGetContextClassLoader() throws LogConfigurationException { |
| ClassLoader classLoader = null; |
| |
| try { |
| classLoader = Thread.currentThread().getContextClassLoader(); |
| } catch (SecurityException ex) { |
| /** |
| * getContextClassLoader() throws SecurityException when |
| * the context class loader isn't an ancestor of the |
| * calling class's class loader, or if security |
| * permissions are restricted. |
| * |
| * We ignore this exception to be consistent with the previous |
| * behavior (e.g. 1.1.3 and earlier). |
| */ |
| // ignore |
| } |
| |
| // Return the selected class loader |
| return classLoader; |
| } |
| |
| /** |
| * Check cached factories (keyed by contextClassLoader) |
| * |
| * @param contextClassLoader is the context classloader associated |
| * with the current thread. This allows separate LogFactory objects |
| * per component within a container, provided each component has |
| * a distinct context classloader set. This parameter may be null |
| * in JDK1.1, and in embedded systems where jcl-using code is |
| * placed in the bootclasspath. |
| * |
| * @return the factory associated with the specified classloader if |
| * one has previously been created, or null if this is the first time |
| * we have seen this particular classloader. |
| */ |
| private static LogFactory getCachedFactory(ClassLoader contextClassLoader) { |
| if (contextClassLoader == null) { |
| // We have to handle this specially, as factories is a Hashtable |
| // and those don't accept null as a key value. |
| // |
| // nb: nullClassLoaderFactory might be null. That's ok. |
| return nullClassLoaderFactory; |
| } else { |
| return (LogFactory) factories.get(contextClassLoader); |
| } |
| } |
| |
| /** |
| * Remember this factory, so later calls to LogFactory.getCachedFactory |
| * can return the previously created object (together with all its |
| * cached Log objects). |
| * |
| * @param classLoader should be the current context classloader. Note that |
| * this can be null under some circumstances; this is ok. |
| * @param factory should be the factory to cache. This should never be null. |
| */ |
| private static void cacheFactory(ClassLoader classLoader, LogFactory factory) { |
| // Ideally we would assert(factory != null) here. However reporting |
| // errors from within a logging implementation is a little tricky! |
| |
| if (factory != null) { |
| if (classLoader == null) { |
| nullClassLoaderFactory = factory; |
| } else { |
| factories.put(classLoader, factory); |
| } |
| } |
| } |
| |
| /** |
| * Return a new instance of the specified <code>LogFactory</code> |
| * implementation class, loaded by the specified class loader. |
| * If that fails, try the class loader used to load this |
| * (abstract) LogFactory. |
| * <h2>ClassLoader conflicts</h2> |
| * <p> |
| * Note that there can be problems if the specified ClassLoader is not the |
| * same as the classloader that loaded this class, ie when loading a |
| * concrete LogFactory subclass via a context classloader. |
| * <p> |
| * The problem is the same one that can occur when loading a concrete Log |
| * subclass via a context classloader. |
| * <p> |
| * The problem occurs when code running in the context classloader calls |
| * class X which was loaded via a parent classloader, and class X then calls |
| * LogFactory.getFactory (either directly or via LogFactory.getLog). Because |
| * class X was loaded via the parent, it binds to LogFactory loaded via |
| * the parent. When the code in this method finds some LogFactoryYYYY |
| * class in the child (context) classloader, and there also happens to be a |
| * LogFactory class defined in the child classloader, then LogFactoryYYYY |
| * will be bound to LogFactory@childloader. It cannot be cast to |
| * LogFactory@parentloader, ie this method cannot return the object as |
| * the desired type. Note that it doesn't matter if the LogFactory class |
| * in the child classloader is identical to the LogFactory class in the |
| * parent classloader, they are not compatible. |
| * <p> |
| * The solution taken here is to simply print out an error message when |
| * this occurs then throw an exception. The deployer of the application |
| * must ensure they remove all occurrences of the LogFactory class from |
| * the child classloader in order to resolve the issue. Note that they |
| * do not have to move the custom LogFactory subclass; that is ok as |
| * long as the only LogFactory class it can find to bind to is in the |
| * parent classloader. |
| * |
| * @param factoryClass Fully qualified name of the <code>LogFactory</code> |
| * implementation class |
| * @param classLoader ClassLoader from which to load this class |
| * @param contextClassLoader is the context that this new factory will |
| * manage logging for. |
| * @throws LogConfigurationException if a suitable instance |
| * cannot be created |
| * @since 1.1 |
| */ |
| protected static LogFactory newFactory(final String factoryClass, |
| final ClassLoader classLoader, |
| final ClassLoader contextClassLoader) |
| throws LogConfigurationException { |
| // Note that any unchecked exceptions thrown by the createFactory |
| // method will propagate out of this method; in particular a |
| // ClassCastException can be thrown. |
| Object result = AccessController.doPrivileged( |
| new PrivilegedAction() { |
| public Object run() { |
| return createFactory(factoryClass, classLoader); |
| } |
| }); |
| |
| if (result instanceof LogConfigurationException) { |
| LogConfigurationException ex = (LogConfigurationException) result; |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("An error occurred while loading the factory class:" + ex.getMessage()); |
| } |
| throw ex; |
| } |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Created object " + objectId(result) + " to manage classloader " + |
| objectId(contextClassLoader)); |
| } |
| return (LogFactory)result; |
| } |
| |
| /** |
| * Method provided for backwards compatibility; see newFactory version that |
| * takes 3 parameters. |
| * <p> |
| * This method would only ever be called in some rather odd situation. |
| * Note that this method is static, so overriding in a subclass doesn't |
| * have any effect unless this method is called from a method in that |
| * subclass. However this method only makes sense to use from the |
| * getFactory method, and as that is almost always invoked via |
| * LogFactory.getFactory, any custom definition in a subclass would be |
| * pointless. Only a class with a custom getFactory method, then invoked |
| * directly via CustomFactoryImpl.getFactory or similar would ever call |
| * this. Anyway, it's here just in case, though the "managed class loader" |
| * value output to the diagnostics will not report the correct value. |
| */ |
| protected static LogFactory newFactory(final String factoryClass, |
| final ClassLoader classLoader) { |
| return newFactory(factoryClass, classLoader, null); |
| } |
| |
| /** |
| * Implements the operations described in the javadoc for newFactory. |
| * |
| * @param factoryClass |
| * @param classLoader used to load the specified factory class. This is |
| * expected to be either the TCCL or the classloader which loaded this |
| * class. Note that the classloader which loaded this class might be |
| * "null" (ie the bootloader) for embedded systems. |
| * @return either a LogFactory object or a LogConfigurationException object. |
| * @since 1.1 |
| */ |
| protected static Object createFactory(String factoryClass, ClassLoader classLoader) { |
| // This will be used to diagnose bad configurations |
| // and allow a useful message to be sent to the user |
| Class logFactoryClass = null; |
| try { |
| if (classLoader != null) { |
| try { |
| // First the given class loader param (thread class loader) |
| |
| // Warning: must typecast here & allow exception |
| // to be generated/caught & recast properly. |
| logFactoryClass = classLoader.loadClass(factoryClass); |
| if (LogFactory.class.isAssignableFrom(logFactoryClass)) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Loaded class " + logFactoryClass.getName() + |
| " from classloader " + objectId(classLoader)); |
| } |
| } else { |
| // |
| // This indicates a problem with the ClassLoader tree. |
| // An incompatible ClassLoader was used to load the |
| // implementation. |
| // As the same classes |
| // must be available in multiple class loaders, |
| // it is very likely that multiple JCL jars are present. |
| // The most likely fix for this |
| // problem is to remove the extra JCL jars from the |
| // ClassLoader hierarchy. |
| // |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Factory class " + logFactoryClass.getName() + |
| " loaded from classloader " + objectId(logFactoryClass.getClassLoader()) + |
| " does not extend '" + LogFactory.class.getName() + |
| "' as loaded by this classloader."); |
| logHierarchy("[BAD CL TREE] ", classLoader); |
| } |
| } |
| |
| return (LogFactory) logFactoryClass.newInstance(); |
| |
| } catch (ClassNotFoundException ex) { |
| if (classLoader == thisClassLoader) { |
| // Nothing more to try, onwards. |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Unable to locate any class called '" + factoryClass + |
| "' via classloader " + objectId(classLoader)); |
| } |
| throw ex; |
| } |
| // ignore exception, continue |
| } catch (NoClassDefFoundError e) { |
| if (classLoader == thisClassLoader) { |
| // Nothing more to try, onwards. |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Class '" + factoryClass + "' cannot be loaded" + |
| " via classloader " + objectId(classLoader) + |
| " - it depends on some other class that cannot be found."); |
| } |
| throw e; |
| } |
| // ignore exception, continue |
| } catch (ClassCastException e) { |
| if (classLoader == thisClassLoader) { |
| // There's no point in falling through to the code below that |
| // tries again with thisClassLoader, because we've just tried |
| // loading with that loader (not the TCCL). Just throw an |
| // appropriate exception here. |
| |
| final boolean implementsLogFactory = implementsLogFactory(logFactoryClass); |
| |
| // |
| // Construct a good message: users may not actual expect that a custom implementation |
| // has been specified. Several well known containers use this mechanism to adapt JCL |
| // to their native logging system. |
| // |
| final StringBuffer msg = new StringBuffer(); |
| msg.append("The application has specified that a custom LogFactory implementation "); |
| msg.append("should be used but Class '"); |
| msg.append(factoryClass); |
| msg.append("' cannot be converted to '"); |
| msg.append(LogFactory.class.getName()); |
| msg.append("'. "); |
| if (implementsLogFactory) { |
| msg.append("The conflict is caused by the presence of multiple LogFactory classes "); |
| msg.append("in incompatible classloaders. "); |
| msg.append("Background can be found in http://commons.apache.org/logging/tech.html. "); |
| msg.append("If you have not explicitly specified a custom LogFactory then it is likely "); |
| msg.append("that the container has set one without your knowledge. "); |
| msg.append("In this case, consider using the commons-logging-adapters.jar file or "); |
| msg.append("specifying the standard LogFactory from the command line. "); |
| } else { |
| msg.append("Please check the custom implementation. "); |
| } |
| msg.append("Help can be found @http://commons.apache.org/logging/troubleshooting.html."); |
| |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic(msg.toString()); |
| } |
| |
| throw new ClassCastException(msg.toString()); |
| } |
| |
| // Ignore exception, continue. Presumably the classloader was the |
| // TCCL; the code below will try to load the class via thisClassLoader. |
| // This will handle the case where the original calling class is in |
| // a shared classpath but the TCCL has a copy of LogFactory and the |
| // specified LogFactory implementation; we will fall back to using the |
| // LogFactory implementation from the same classloader as this class. |
| // |
| // Issue: this doesn't handle the reverse case, where this LogFactory |
| // is in the webapp, and the specified LogFactory implementation is |
| // in a shared classpath. In that case: |
| // (a) the class really does implement LogFactory (bad log msg above) |
| // (b) the fallback code will result in exactly the same problem. |
| } |
| } |
| |
| /* At this point, either classLoader == null, OR |
| * classLoader was unable to load factoryClass. |
| * |
| * In either case, we call Class.forName, which is equivalent |
| * to LogFactory.class.getClassLoader().load(name), ie we ignore |
| * the classloader parameter the caller passed, and fall back |
| * to trying the classloader associated with this class. See the |
| * javadoc for the newFactory method for more info on the |
| * consequences of this. |
| * |
| * Notes: |
| * * LogFactory.class.getClassLoader() may return 'null' |
| * if LogFactory is loaded by the bootstrap classloader. |
| */ |
| // Warning: must typecast here & allow exception |
| // to be generated/caught & recast properly. |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Unable to load factory class via classloader " + objectId(classLoader) + |
| " - trying the classloader associated with this LogFactory."); |
| } |
| logFactoryClass = Class.forName(factoryClass); |
| return (LogFactory) logFactoryClass.newInstance(); |
| } catch (Exception e) { |
| // Check to see if we've got a bad configuration |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Unable to create LogFactory instance."); |
| } |
| if (logFactoryClass != null && !LogFactory.class.isAssignableFrom(logFactoryClass)) { |
| return new LogConfigurationException( |
| "The chosen LogFactory implementation does not extend LogFactory." + |
| " Please check your configuration.", e); |
| } |
| return new LogConfigurationException(e); |
| } |
| } |
| |
| /** |
| * Determines whether the given class actually implements <code>LogFactory</code>. |
| * Diagnostic information is also logged. |
| * <p> |
| * <strong>Usage:</strong> to diagnose whether a classloader conflict is the cause |
| * of incompatibility. The test used is whether the class is assignable from |
| * the <code>LogFactory</code> class loaded by the class's classloader. |
| * @param logFactoryClass <code>Class</code> which may implement <code>LogFactory</code> |
| * @return true if the <code>logFactoryClass</code> does extend |
| * <code>LogFactory</code> when that class is loaded via the same |
| * classloader that loaded the <code>logFactoryClass</code>. |
| */ |
| private static boolean implementsLogFactory(Class logFactoryClass) { |
| boolean implementsLogFactory = false; |
| if (logFactoryClass != null) { |
| try { |
| ClassLoader logFactoryClassLoader = logFactoryClass.getClassLoader(); |
| if (logFactoryClassLoader == null) { |
| logDiagnostic("[CUSTOM LOG FACTORY] was loaded by the boot classloader"); |
| } else { |
| logHierarchy("[CUSTOM LOG FACTORY] ", logFactoryClassLoader); |
| Class factoryFromCustomLoader |
| = Class.forName("org.apache.commons.logging.LogFactory", false, logFactoryClassLoader); |
| implementsLogFactory = factoryFromCustomLoader.isAssignableFrom(logFactoryClass); |
| if (implementsLogFactory) { |
| logDiagnostic("[CUSTOM LOG FACTORY] " + logFactoryClass.getName() + |
| " implements LogFactory but was loaded by an incompatible classloader."); |
| } else { |
| logDiagnostic("[CUSTOM LOG FACTORY] " + logFactoryClass.getName() + |
| " does not implement LogFactory."); |
| } |
| } |
| } catch (SecurityException e) { |
| // |
| // The application is running within a hostile security environment. |
| // This will make it very hard to diagnose issues with JCL. |
| // Consider running less securely whilst debugging this issue. |
| // |
| logDiagnostic("[CUSTOM LOG FACTORY] SecurityException thrown whilst trying to determine whether " + |
| "the compatibility was caused by a classloader conflict: " + e.getMessage()); |
| } catch (LinkageError e) { |
| // |
| // This should be an unusual circumstance. |
| // LinkageError's usually indicate that a dependent class has incompatibly changed. |
| // Another possibility may be an exception thrown by an initializer. |
| // Time for a clean rebuild? |
| // |
| logDiagnostic("[CUSTOM LOG FACTORY] LinkageError thrown whilst trying to determine whether " + |
| "the compatibility was caused by a classloader conflict: " + e.getMessage()); |
| } catch (ClassNotFoundException e) { |
| // |
| // LogFactory cannot be loaded by the classloader which loaded the custom factory implementation. |
| // The custom implementation is not viable until this is corrected. |
| // Ensure that the JCL jar and the custom class are available from the same classloader. |
| // Running with diagnostics on should give information about the classloaders used |
| // to load the custom factory. |
| // |
| logDiagnostic("[CUSTOM LOG FACTORY] LogFactory class cannot be loaded by classloader which loaded " + |
| "the custom LogFactory implementation. Is the custom factory in the right classloader?"); |
| } |
| } |
| return implementsLogFactory; |
| } |
| |
| /** |
| * Applets may run in an environment where accessing resources of a loader is |
| * a secure operation, but where the commons-logging library has explicitly |
| * been granted permission for that operation. In this case, we need to |
| * run the operation using an AccessController. |
| */ |
| private static InputStream getResourceAsStream(final ClassLoader loader, final String name) { |
| return (InputStream)AccessController.doPrivileged( |
| new PrivilegedAction() { |
| public Object run() { |
| if (loader != null) { |
| return loader.getResourceAsStream(name); |
| } else { |
| return ClassLoader.getSystemResourceAsStream(name); |
| } |
| } |
| }); |
| } |
| |
| /** |
| * Given a filename, return an enumeration of URLs pointing to |
| * all the occurrences of that filename in the classpath. |
| * <p> |
| * This is just like ClassLoader.getResources except that the |
| * operation is done under an AccessController so that this method will |
| * succeed when this jarfile is privileged but the caller is not. |
| * This method must therefore remain private to avoid security issues. |
| * <p> |
| * If no instances are found, an Enumeration is returned whose |
| * hasMoreElements method returns false (ie an "empty" enumeration). |
| * If resources could not be listed for some reason, null is returned. |
| */ |
| private static Enumeration getResources(final ClassLoader loader, final String name) { |
| PrivilegedAction action = |
| new PrivilegedAction() { |
| public Object run() { |
| try { |
| if (loader != null) { |
| return loader.getResources(name); |
| } else { |
| return ClassLoader.getSystemResources(name); |
| } |
| } catch (IOException e) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Exception while trying to find configuration file " + |
| name + ":" + e.getMessage()); |
| } |
| return null; |
| } catch (NoSuchMethodError e) { |
| // we must be running on a 1.1 JVM which doesn't support |
| // ClassLoader.getSystemResources; just return null in |
| // this case. |
| return null; |
| } |
| } |
| }; |
| Object result = AccessController.doPrivileged(action); |
| return (Enumeration) result; |
| } |
| |
| /** |
| * Given a URL that refers to a .properties file, load that file. |
| * This is done under an AccessController so that this method will |
| * succeed when this jarfile is privileged but the caller is not. |
| * This method must therefore remain private to avoid security issues. |
| * <p> |
| * {@code Null} is returned if the URL cannot be opened. |
| */ |
| private static Properties getProperties(final URL url) { |
| PrivilegedAction action = |
| new PrivilegedAction() { |
| public Object run() { |
| InputStream stream = null; |
| try { |
| // We must ensure that useCaches is set to false, as the |
| // default behavior of java is to cache file handles, and |
| // this "locks" files, preventing hot-redeploy on windows. |
| URLConnection connection = url.openConnection(); |
| connection.setUseCaches(false); |
| stream = connection.getInputStream(); |
| if (stream != null) { |
| Properties props = new Properties(); |
| props.load(stream); |
| stream.close(); |
| stream = null; |
| return props; |
| } |
| } catch (IOException e) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Unable to read URL " + url); |
| } |
| } finally { |
| if (stream != null) { |
| try { |
| stream.close(); |
| } catch (IOException e) { |
| // ignore exception; this should not happen |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("Unable to close stream for URL " + url); |
| } |
| } |
| } |
| } |
| |
| return null; |
| } |
| }; |
| return (Properties) AccessController.doPrivileged(action); |
| } |
| |
| /** |
| * Locate a user-provided configuration file. |
| * <p> |
| * The classpath of the specified classLoader (usually the context classloader) |
| * is searched for properties files of the specified name. If none is found, |
| * null is returned. If more than one is found, then the file with the greatest |
| * value for its PRIORITY property is returned. If multiple files have the |
| * same PRIORITY value then the first in the classpath is returned. |
| * <p> |
| * This differs from the 1.0.x releases; those always use the first one found. |
| * However as the priority is a new field, this change is backwards compatible. |
| * <p> |
| * The purpose of the priority field is to allow a webserver administrator to |
| * override logging settings in all webapps by placing a commons-logging.properties |
| * file in a shared classpath location with a priority > 0; this overrides any |
| * commons-logging.properties files without priorities which are in the |
| * webapps. Webapps can also use explicit priorities to override a configuration |
| * file in the shared classpath if needed. |
| */ |
| private static final Properties getConfigurationFile(ClassLoader classLoader, String fileName) { |
| Properties props = null; |
| double priority = 0.0; |
| URL propsUrl = null; |
| try { |
| Enumeration urls = getResources(classLoader, fileName); |
| |
| if (urls == null) { |
| return null; |
| } |
| |
| while (urls.hasMoreElements()) { |
| URL url = (URL) urls.nextElement(); |
| |
| Properties newProps = getProperties(url); |
| if (newProps != null) { |
| if (props == null) { |
| propsUrl = url; |
| props = newProps; |
| String priorityStr = props.getProperty(PRIORITY_KEY); |
| priority = 0.0; |
| if (priorityStr != null) { |
| priority = Double.parseDouble(priorityStr); |
| } |
| |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] Properties file found at '" + url + "'" + |
| " with priority " + priority); |
| } |
| } else { |
| String newPriorityStr = newProps.getProperty(PRIORITY_KEY); |
| double newPriority = 0.0; |
| if (newPriorityStr != null) { |
| newPriority = Double.parseDouble(newPriorityStr); |
| } |
| |
| if (newPriority > priority) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] Properties file at '" + url + "'" + |
| " with priority " + newPriority + |
| " overrides file at '" + propsUrl + "'" + |
| " with priority " + priority); |
| } |
| |
| propsUrl = url; |
| props = newProps; |
| priority = newPriority; |
| } else { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("[LOOKUP] Properties file at '" + url + "'" + |
| " with priority " + newPriority + |
| " does not override file at '" + propsUrl + "'" + |
| " with priority " + priority); |
| } |
| } |
| } |
| |
| } |
| } |
| } catch (SecurityException e) { |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("SecurityException thrown while trying to find/read config files."); |
| } |
| } |
| |
| if (isDiagnosticsEnabled()) { |
| if (props == null) { |
| logDiagnostic("[LOOKUP] No properties file of name '" + fileName + "' found."); |
| } else { |
| logDiagnostic("[LOOKUP] Properties file of name '" + fileName + "' found at '" + propsUrl + '"'); |
| } |
| } |
| |
| return props; |
| } |
| |
| /** |
| * 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. |
| * <p> |
| * 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); |
| } |
| }); |
| } |
| |
| /** |
| * Determines whether the user wants internal diagnostic output. If so, |
| * returns an appropriate writer object. Users can enable diagnostic |
| * output by setting the system property named {@link #DIAGNOSTICS_DEST_PROPERTY} to |
| * a filename, or the special values STDOUT or STDERR. |
| */ |
| private static PrintStream initDiagnostics() { |
| String dest; |
| try { |
| dest = getSystemProperty(DIAGNOSTICS_DEST_PROPERTY, null); |
| if (dest == null) { |
| return null; |
| } |
| } catch (SecurityException ex) { |
| // We must be running in some very secure environment. |
| // We just have to assume output is not wanted.. |
| return null; |
| } |
| |
| if (dest.equals("STDOUT")) { |
| return System.out; |
| } else if (dest.equals("STDERR")) { |
| return System.err; |
| } else { |
| try { |
| // open the file in append mode |
| FileOutputStream fos = new FileOutputStream(dest, true); |
| return new PrintStream(fos); |
| } catch (IOException ex) { |
| // We should report this to the user - but how? |
| return null; |
| } |
| } |
| } |
| |
| /** |
| * Indicates true if the user has enabled internal logging. |
| * <p> |
| * By the way, sorry for the incorrect grammar, but calling this method |
| * areDiagnosticsEnabled just isn't java beans style. |
| * |
| * @return true if calls to logDiagnostic will have any effect. |
| * @since 1.1 |
| */ |
| protected static boolean isDiagnosticsEnabled() { |
| return diagnosticsStream != null; |
| } |
| |
| /** |
| * Write the specified message to the internal logging destination. |
| * <p> |
| * Note that this method is private; concrete subclasses of this class |
| * should not call it because the diagnosticPrefix string this |
| * method puts in front of all its messages is LogFactory@...., |
| * while subclasses should put SomeSubClass@... |
| * <p> |
| * Subclasses should instead compute their own prefix, then call |
| * logRawDiagnostic. Note that calling isDiagnosticsEnabled is |
| * fine for subclasses. |
| * <p> |
| * Note that it is safe to call this method before initDiagnostics |
| * is called; any output will just be ignored (as isDiagnosticsEnabled |
| * will return false). |
| * |
| * @param msg is the diagnostic message to be output. |
| */ |
| private static final void logDiagnostic(String msg) { |
| if (diagnosticsStream != null) { |
| diagnosticsStream.print(diagnosticPrefix); |
| diagnosticsStream.println(msg); |
| diagnosticsStream.flush(); |
| } |
| } |
| |
| /** |
| * Write the specified message to the internal logging destination. |
| * |
| * @param msg is the diagnostic message to be output. |
| * @since 1.1 |
| */ |
| protected static final void logRawDiagnostic(String msg) { |
| if (diagnosticsStream != null) { |
| diagnosticsStream.println(msg); |
| diagnosticsStream.flush(); |
| } |
| } |
| |
| /** |
| * Generate useful diagnostics regarding the classloader tree for |
| * the specified class. |
| * <p> |
| * As an example, if the specified class was loaded via a webapp's |
| * classloader, then you may get the following output: |
| * <pre> |
| * Class com.acme.Foo was loaded via classloader 11111 |
| * ClassLoader tree: 11111 -> 22222 (SYSTEM) -> 33333 -> BOOT |
| * </pre> |
| * <p> |
| * This method returns immediately if isDiagnosticsEnabled() |
| * returns false. |
| * |
| * @param clazz is the class whose classloader + tree are to be |
| * output. |
| */ |
| private static void logClassLoaderEnvironment(Class clazz) { |
| if (!isDiagnosticsEnabled()) { |
| return; |
| } |
| |
| try { |
| // Deliberately use System.getProperty here instead of getSystemProperty; if |
| // the overall security policy for the calling application forbids access to |
| // these variables then we do not want to output them to the diagnostic stream. |
| logDiagnostic("[ENV] Extension directories (java.ext.dir): " + System.getProperty("java.ext.dir")); |
| logDiagnostic("[ENV] Application classpath (java.class.path): " + System.getProperty("java.class.path")); |
| } catch (SecurityException ex) { |
| logDiagnostic("[ENV] Security setting prevent interrogation of system classpaths."); |
| } |
| |
| String className = clazz.getName(); |
| ClassLoader classLoader; |
| |
| try { |
| classLoader = getClassLoader(clazz); |
| } catch (SecurityException ex) { |
| // not much useful diagnostics we can print here! |
| logDiagnostic("[ENV] Security forbids determining the classloader for " + className); |
| return; |
| } |
| |
| logDiagnostic("[ENV] Class " + className + " was loaded via classloader " + objectId(classLoader)); |
| logHierarchy("[ENV] Ancestry of classloader which loaded " + className + " is ", classLoader); |
| } |
| |
| /** |
| * Logs diagnostic messages about the given classloader |
| * and it's hierarchy. The prefix is prepended to the message |
| * and is intended to make it easier to understand the logs. |
| * @param prefix |
| * @param classLoader |
| */ |
| private static void logHierarchy(String prefix, ClassLoader classLoader) { |
| if (!isDiagnosticsEnabled()) { |
| return; |
| } |
| ClassLoader systemClassLoader; |
| if (classLoader != null) { |
| final String classLoaderString = classLoader.toString(); |
| logDiagnostic(prefix + objectId(classLoader) + " == '" + classLoaderString + "'"); |
| } |
| |
| try { |
| systemClassLoader = ClassLoader.getSystemClassLoader(); |
| } catch (SecurityException ex) { |
| logDiagnostic(prefix + "Security forbids determining the system classloader."); |
| return; |
| } |
| if (classLoader != null) { |
| final StringBuffer buf = new StringBuffer(prefix + "ClassLoader tree:"); |
| for(;;) { |
| buf.append(objectId(classLoader)); |
| if (classLoader == systemClassLoader) { |
| buf.append(" (SYSTEM) "); |
| } |
| |
| try { |
| classLoader = classLoader.getParent(); |
| } catch (SecurityException ex) { |
| buf.append(" --> SECRET"); |
| break; |
| } |
| |
| buf.append(" --> "); |
| if (classLoader == null) { |
| buf.append("BOOT"); |
| break; |
| } |
| } |
| logDiagnostic(buf.toString()); |
| } |
| } |
| |
| /** |
| * Returns a string that uniquely identifies the specified object, including |
| * its class. |
| * <p> |
| * The returned string is of form "classname@hashcode", ie is the same as |
| * the return value of the Object.toString() method, but works even when |
| * the specified object's class has overidden the toString method. |
| * |
| * @param o may be null. |
| * @return a string of form classname@hashcode, or "null" if param o is null. |
| * @since 1.1 |
| */ |
| public static String objectId(Object o) { |
| if (o == null) { |
| return "null"; |
| } else { |
| return o.getClass().getName() + "@" + System.identityHashCode(o); |
| } |
| } |
| |
| // ---------------------------------------------------------------------- |
| // Static initialiser block to perform initialisation at class load time. |
| // |
| // We can't do this in the class constructor, as there are many |
| // static methods on this class that can be called before any |
| // LogFactory instances are created, and they depend upon this |
| // stuff having been set up. |
| // |
| // Note that this block must come after any variable declarations used |
| // by any methods called from this block, as we want any static initialiser |
| // associated with the variable to run first. If static initialisers for |
| // variables run after this code, then (a) their value might be needed |
| // by methods called from here, and (b) they might *override* any value |
| // computed here! |
| // |
| // So the wisest thing to do is just to place this code at the very end |
| // of the class file. |
| // ---------------------------------------------------------------------- |
| |
| static { |
| // note: it's safe to call methods before initDiagnostics (though |
| // diagnostic output gets discarded). |
| thisClassLoader = getClassLoader(LogFactory.class); |
| // In order to avoid confusion where multiple instances of JCL are |
| // being used via different classloaders within the same app, we |
| // ensure each logged message has a prefix of form |
| // [LogFactory from classloader OID] |
| // |
| // Note that this prefix should be kept consistent with that |
| // in LogFactoryImpl. However here we don't need to output info |
| // about the actual *instance* of LogFactory, as all methods that |
| // output diagnostics from this class are static. |
| String classLoaderName; |
| try { |
| ClassLoader classLoader = thisClassLoader; |
| if (thisClassLoader == null) { |
| classLoaderName = "BOOTLOADER"; |
| } else { |
| classLoaderName = objectId(classLoader); |
| } |
| } catch (SecurityException e) { |
| classLoaderName = "UNKNOWN"; |
| } |
| diagnosticPrefix = "[LogFactory from " + classLoaderName + "] "; |
| diagnosticsStream = initDiagnostics(); |
| logClassLoaderEnvironment(LogFactory.class); |
| factories = createFactoryStore(); |
| if (isDiagnosticsEnabled()) { |
| logDiagnostic("BOOTSTRAP COMPLETED"); |
| } |
| } |
| } |
