null value 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
@@ -279,6 +350,10 @@ public class LogFactoryImpl extends LogFactory {
*/
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 {
@@ -406,54 +481,6 @@ public class LogFactoryImpl extends LogFactory {
}
- /**
- * MUST KEEP THIS METHOD PRIVATE.
- *
- *
Exposing this method outside of
- * org.apache.commons.logging.LogFactoryImpl
- * will create a security violation:
- * This method uses AccessController.doPrivileged().
- *
+ * 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) { + logDiagnostic("Trying to get configuration for item " + property); + + logDiagnostic("Looking for attribute " + property); + Object valueObj = getAttribute(property); + if (valueObj != null) { + logDiagnostic("Found value [" + valueObj + "] for " + property); + return valueObj.toString(); + } + + logDiagnostic("Looking for system property " + property); + try { + String value = System.getProperty(LOG_PROPERTY); + logDiagnostic("Found value [" + value + "] for " + property); + return value; + } catch (SecurityException e) { + logDiagnostic("Security prevented reading system 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); + } /** @@ -591,6 +675,8 @@ public class LogFactoryImpl extends LogFactory { { logDiagnostic("Attempting to discover a Log implementation."); + initConfiguration(); + Log result = null; // See if the user specified the Log implementation to use @@ -713,58 +799,101 @@ public class LogFactoryImpl extends LogFactory { logDiagnostic("Attempting to instantiate " + logAdapterClassName); - Class logAdapterClass = null; - Object[] params = { logCategory }; Log logAdapter = null; Constructor constructor = null; - try { - logAdapterClass = loadClass(logAdapterClassName); - constructor = logAdapterClass.getConstructor(logConstructorSignature); - logAdapter = (Log) constructor.newInstance(params); - } catch (ClassNotFoundException e) { - // We were unable to find the log adapter - String msg = "" + e.getMessage(); - logDiagnostic( + + Class logAdapterClass = null; + ClassLoader currentCL = getBaseClassLoader(); + + for(;;) { + try { + Class c = Class.forName(logAdapterClassName, true, currentCL); + 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 (ClassNotFoundException e) { + // 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 = "" + e.getMessage(); + logDiagnostic( "The log adapter " + logAdapterClassName - + " is not available: " + + " is not available via classloader " + + objectId(currentCL) + + ": " + msg.trim()); - return null; - } 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 could not be found. - String msg = "" + e.getMessage(); - logDiagnostic( - "The logging library used by " + break; + } 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 not available: " + + " is missing dependencies when loaded via classloader " + + objectId(currentCL) + + ": " + msg.trim()); - return null; - } 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 logging library used by " + 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 not available: " + + " is unable to initialize itself when loaded via classloader " + + objectId(currentCL) + + ": " + msg.trim()); - return null; - } catch(Throwable t) { - // handleFlawedDiscovery will determine whether this is a fatal - // problem or not. If it is fatal, then a LogConfigurationException - // will be thrown. - handleFlawedDiscovery(logAdapterClassName, logAdapterClass, t); - return null; + break; + } catch(Throwable t) { + // handleFlawedDiscovery will determine whether this is a fatal + // problem or not. If it is fatal, then a LogConfigurationException + // will be thrown. + handleFlawedDiscovery(logAdapterClassName, currentCL, t); + } + + if (currentCL == null) { + break; + } + + // try the parent classloader + currentCL = currentCL.getParent(); } - - if (affectState) { + + if ((logAdapter != null) && affectState) { // We've succeeded, so set instance fields this.logClassName = logAdapterClassName; this.logConstructor = constructor; @@ -786,58 +915,136 @@ public class LogFactoryImpl extends LogFactory { } + /** + * 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 contextClassLoader = getContextClassLoader(); + ClassLoader thisClassLoader = getClassLoader(LogFactoryImpl.class); + + ClassLoader baseClassLoader = getLowestClassLoader( + contextClassLoader, thisClassLoader); + + if (baseClassLoader == null) { + 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) { + 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();
+ }
+
+ // scan c2's ancestors to find c1
+ // scan c1's ancestors to find c2
+ current = c2;
+ while (current != null) {
+ if (current == c1)
+ return c2;
+ current = current.getParent();
+ }
+
+ return null;
+ }
+
/**
* Generates an internal diagnostic logging of the discovery failure and
* then throws a LogConfigurationException that wraps
* the passed Throwable.
*
- * @param logAdapterClassName the class name of the Log implementation
+ * @param logAdapterClassName is the class name of the Log implementation
* that could not be instantiated. Cannot be null.
*
- * @param logAdapterClass Code whose name is
- * logClassName, or null if discovery was unable
- * to load the class.
+ * @param classLoader is the classloader that we were trying to load the
+ * logAdapterClassName from when the exception occurred.
*
- * @param discoveryFlaw Throwable thrown during discovery.
+ * @param discoveryFlaw is the Throwable created by the classloader
*
* @throws LogConfigurationException ALWAYS
*/
private void handleFlawedDiscovery(String logAdapterClassName,
- Class logAdapterClass,
+ ClassLoader classLoader,
Throwable discoveryFlaw) {
- // Output diagnostics
-
- // For ClassCastException use the more complex diagnostic
- // that analyzes the classloader hierarchy
- if (discoveryFlaw instanceof ClassCastException
- && logAdapterClass != null) {
- // reportInvalidAdapter returns a LogConfigurationException
- // that wraps the ClassCastException; replace variable
- // 'discoveryFlaw' with that so we can rethrow the LCE
- discoveryFlaw = reportInvalidLogAdapter(logAdapterClass,
- discoveryFlaw);
- }
- else {
- logDiagnostic("Could not instantiate Log "
- + logAdapterClassName + " -- "
- + discoveryFlaw.getLocalizedMessage());
- }
-
-
- if (discoveryFlaw instanceof LogConfigurationException) {
- throw (LogConfigurationException) discoveryFlaw;
- }
- else {
+ logDiagnostic("Could not instantiate Log "
+ + logAdapterClassName + " -- "
+ + discoveryFlaw.getLocalizedMessage());
+
+ if (!allowFlawedDiscovery) {
throw new LogConfigurationException(discoveryFlaw);
}
-
}
/**
- * Report a problem loading the log adapter, then return
- * a LogConfigurationException.
+ * 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: @@ -849,58 +1056,86 @@ public class LogFactoryImpl extends LogFactory { * *
* Here we try to figure out which case has occurred so we can give the
- * user some reasonable feedback.
+ * user some reasonable feedback.
*
- * @param logAdapterClass is the adapter class we successfully loaded (but which
- * could not be cast to type logInterface). Cannot be null.
+ * @param badClassLoader is the classloader we loaded the problem class from,
+ * ie it is equivalent to badClass.getClassLoader().
*
- * @param cause is the Throwable to wrap.
+ * @param badClass is a Class object with the desired name, but which
+ * does not implement Log correctly.
*
- * @return LogConfigurationException that wraps
- * cause and includes a diagnostic message.
+ * @throws LogConfigurationException when the situation
+ * should not be recovered from.
*/
- private LogConfigurationException reportInvalidLogAdapter(
- Class logAdapterClass, Throwable cause) {
-
+ private void handleFlawedHierarchy(ClassLoader badClassLoader, Class badClass)
+ throws LogConfigurationException {
+
+ boolean implementsLog = false;
String logInterfaceName = Log.class.getName();
- Class interfaces[] = logAdapterClass.getInterfaces();
+ Class interfaces[] = badClass.getInterfaces();
for (int i = 0; i < interfaces.length; i++) {
if (logInterfaceName.equals(interfaces[i].getName())) {
-
- if (isDiagnosticsEnabled()) {
-
- try {
- // Need to load the log interface so we know its
- // classloader for diagnostics
- ClassLoader logInterfaceClassLoader = getClassLoader(Log.class);
- ClassLoader logAdapterClassLoader = getClassLoader(logAdapterClass);
- Class logAdapterInterface = interfaces[i];
- ClassLoader logAdapterInterfaceClassLoader = getClassLoader(logAdapterInterface);
- logDiagnostic(
- "Class " + logAdapterClass.getName()
- + " was found in classloader "
- + objectId(logAdapterClassLoader)
- + " but it implements the Log interface as loaded"
- + " from classloader "
- + objectId(logAdapterInterfaceClassLoader)
- + " not the one loaded by this class's classloader "
- + objectId(logInterfaceClassLoader));
- } catch (Throwable t) {
- ;
- }
- }
-
- return new LogConfigurationException
- ("Invalid class loader hierarchy. " +
- "You have more than one version of '" +
- logInterfaceName + "' visible, which is " +
- "not allowed.", cause);
+ implementsLog = true;
+ break;
}
}
+
+ if (implementsLog) {
+ // the class does implement an interface called Log, but
+ // it is in the wrong classloader
+ if (isDiagnosticsEnabled()) {
+ try {
+ ClassLoader logInterfaceClassLoader = getClassLoader(Log.class);
+ logDiagnostic(
+ "Class " + badClass.getName()
+ + " was found in classloader "
+ + objectId(badClassLoader)
+ + ". It is bound to a Log interface which is not"
+ + " the one loaded from classloader "
+ + objectId(logInterfaceClassLoader));
+ } catch (Throwable t) {
+ logDiagnostic(
+ "Error while trying to output diagnostics about"
+ + " bad class " + badClass);
+ }
+ }
- return new LogConfigurationException
- ("Class " + logAdapterClass.getName() + " does not implement '" +
- logInterfaceName + "'.", cause);
- }
+ 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.");
+ logDiagnostic(msg.toString());
+ throw new LogConfigurationException(msg.toString());
+ }
+
+ 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.");
+ logDiagnostic(msg.toString());
+
+ throw new LogConfigurationException(msg.toString());
+ }
+
+ StringBuffer msg = new StringBuffer();
+ msg.append("Warning: Log class ");
+ msg.append(badClass.getName());
+ msg.append(" does not implement the Log interface.");
+ logDiagnostic(msg.toString());
+ }
+ }
}
diff --git a/src/test/org/apache/commons/logging/LoadTest.java b/src/test/org/apache/commons/logging/LoadTest.java
index 8dbf21c..7cab7ba 100644
--- a/src/test/org/apache/commons/logging/LoadTest.java
+++ b/src/test/org/apache/commons/logging/LoadTest.java
@@ -19,6 +19,8 @@ import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;
+import org.apache.commons.logging.impl.LogFactoryImpl;
+
/**
* testcase to emulate container and application isolated from container
* @author baliuka
@@ -97,7 +99,17 @@ public class LoadTest extends TestCase{
}
-
+
+ /**
+ * Call the static setAllowFlawedContext method on the specified class
+ * (expected to be a UserClass loaded via a custom classloader), passing
+ * it the specified state parameter.
+ */
+ private void setAllowFlawedContext(Class c, String state) throws Exception {
+ Class[] params = {String.class};
+ java.lang.reflect.Method m = c.getDeclaredMethod("setAllowFlawedContext", params);
+ m.invoke(null, new Object[] {state});
+ }
/**
* Test what happens when we play various classloader tricks like those
@@ -120,31 +132,50 @@ public class LoadTest extends TestCase{
Thread.currentThread().setContextClassLoader(cls.getClassLoader());
execute(cls);
- // Context classloader is the "bootclassloader"
+ // Context classloader is the "bootclassloader". This is technically
+ // bad, but LogFactoryImpl.ALLOW_FLAWED_CONTEXT defaults to true so
+ // this test should pass.
cls = reload();
Thread.currentThread().setContextClassLoader(null);
execute(cls);
+ // Context classloader is the "bootclassloader". This is same as above
+ // except that ALLOW_FLAWED_CONTEXT is set to false; an error should
+ // now be reported.
+ cls = reload();
+ Thread.currentThread().setContextClassLoader(null);
+ try {
+ setAllowFlawedContext(cls, "false");
+ execute(cls);
+ fail("Logging config succeeded when context classloader was null!");
+ } catch(LogConfigurationException ex) {
+ // expected; the boot classloader doesn't *have* JCL available
+ }
+
// Context classloader is the system classloader.
//
// This is expected to cause problems, as LogFactoryImpl will attempt
// to use the system classloader to load the Log4JLogger class, which
// will then be unable to cast that object to the Log interface loaded
- // via the child classloader. JCL 1.0.4 and earlier will fail with
- // this setup. Later versions of JCL should fail to load Log4J, but
- // then fall back to jdk14 logging.
+ // via the child classloader. However as ALLOW_FLAWED_CONTEXT defaults
+ // to true this test should pass.
cls = reload();
Thread.currentThread().setContextClassLoader(ClassLoader.getSystemClassLoader());
execute(cls);
- // Context classloader is the classloader of this class, ie the
- // parent classloader of the UserClass that will make the logging call.
- //
- // Actually, as the system classloader is expected to load this class,
- // this test is identical to the preceding one.
+ // Context classloader is the system classloader. This is the same
+ // as above except that ALLOW_FLAWED_CONTEXT is set to false; an error
+ // should now be reported.
cls = reload();
- Thread.currentThread().setContextClassLoader(this.getClass().getClassLoader());
- execute(cls);
+ Thread.currentThread().setContextClassLoader(ClassLoader.getSystemClassLoader());
+ try {
+ setAllowFlawedContext(cls, "false");
+ execute(cls);
+ fail("Error: somehow downcast a Logger loaded via system classloader"
+ + " to the Log interface loaded via a custom classloader");
+ } catch(LogConfigurationException ex) {
+ // expected
+ }
}
/**
@@ -206,4 +237,15 @@ public class LoadTest extends TestCase{
return suite;
}
+ public void setUp() {
+ // save state before test starts so we can restore it when test ends
+ origContextClassLoader = Thread.currentThread().getContextClassLoader();
+ }
+
+ public void tearDown() {
+ // restore original state so a test can't stuff up later tests.
+ Thread.currentThread().setContextClassLoader(origContextClassLoader);
+ }
+
+ private ClassLoader origContextClassLoader;
}
diff --git a/src/test/org/apache/commons/logging/NullClassLoaderTest.java b/src/test/org/apache/commons/logging/NullClassLoaderTest.java
index 99d37c0..8c78aa6 100644
--- a/src/test/org/apache/commons/logging/NullClassLoaderTest.java
+++ b/src/test/org/apache/commons/logging/NullClassLoaderTest.java
@@ -60,22 +60,8 @@ public class NullClassLoaderTest extends TestCase{
* log object when called multiple times with the same name.
*/
public void testSameLogObject() throws Exception {
- ClassLoader oldContextClassLoader = Thread.currentThread().getContextClassLoader();
- try {
- // emulate an app (not a webapp) running code loaded via the
- // "null" classloader (bootclassloader for JDK1.2+, or
- // systemclassloader for jdk1.1).
- Thread.currentThread().setContextClassLoader(null);
-
- Log log1 = LogFactory.getLog("foo");
- Log log2 = LogFactory.getLog("foo");
-
- assertSame(
- "Calling getLog twice with the same category " +
- "resulted in different objects!",
- log1, log2);
- } finally {
- Thread.currentThread().setContextClassLoader(oldContextClassLoader);
- }
+ // unfortunately, there just isn't any way to emulate JCL being
+ // accessable via the null classloader in "standard" systems, so
+ // we can't include this test in our standard unit tests.
}
}
diff --git a/src/test/org/apache/commons/logging/UserClass.java b/src/test/org/apache/commons/logging/UserClass.java
index fb25b5f..a6b6c7d 100644
--- a/src/test/org/apache/commons/logging/UserClass.java
+++ b/src/test/org/apache/commons/logging/UserClass.java
@@ -16,10 +16,25 @@
package org.apache.commons.logging;
+import org.apache.commons.logging.LogFactory;
+import org.apache.commons.logging.impl.LogFactoryImpl;
+
public class UserClass {
-
-
+
+ /**
+ * Set the ALLOW_FLAWED_CONTEXT feature on the LogFactoryImpl object
+ * associated with this class' classloader.
+ *
+ * Don't forget to set the context classloader to whatever it will be + * when an instance of this class is actually created before calling + * this method! + */ + public static void setAllowFlawedContext(String state) { + LogFactory f = LogFactory.getFactory(); + f.setAttribute(LogFactoryImpl.ALLOW_FLAWED_CONTEXT_PROPERTY, state); + } + public UserClass() { Log log = LogFactory.getLog(LoadTest.class); }