Author: rdonkin
Date: Tue Mar 7 13:54:57 2006
New Revision: 384025
URL: http://svn.apache.org/viewcvs?rev=384025&view=rev
Log:
Improved diagnostics and added more information to the message thrown when a
custom LogFactory cannot be loaded due to classloader incompatibilities.
Modified:
jakarta/commons/proper/logging/trunk/src/java/org/apache/commons/logging/LogFactory.java
Modified:
jakarta/commons/proper/logging/trunk/src/java/org/apache/commons/logging/LogFactory.java
URL:
http://svn.apache.org/viewcvs/jakarta/commons/proper/logging/trunk/src/java/org/apache/commons/logging/LogFactory.java?rev=384025&r1=384024&r2=384025&view=diff
==============================================================================
---
jakarta/commons/proper/logging/trunk/src/java/org/apache/commons/logging/LogFactory.java
(original)
+++
jakarta/commons/proper/logging/trunk/src/java/org/apache/commons/logging/LogFactory.java
Tue Mar 7 13:54:57 2006
@@ -1101,13 +1101,29 @@
// 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.
+ //
String msg =
+ "The application has specified that a custom
LogFactory implementation should be used but " +
"Class '" + factoryClass + "' cannot be converted
to '"
- + LogFactory.class.getName() + "'."
- + " Perhaps you have multiple copies of LogFactory
in"
- + " the classpath? If so, consider using the"
- + " commons-logging-adapters.jar file.";
-
+ + LogFactory.class.getName() + "'. ";
+ if (implementsLogFactory) {
+ msg = msg + "The conflict is caused by the
presence of multiple LogFactory classes in incompatible classloaders. " +
+ "Background can be found in
http://jakarta.apache.org/commons/logging/tech.html. " +
+ "If you have not explicitly specified a custom
LogFactory then it is likely that " +
+ "the container has set one without your
knowledge. " +
+ "In this case, consider using the
commons-logging-adapters.jar file or " +
+ "specifying the standard LogFactory from the
command line. ";
+ } else {
+ msg = msg + "Please check the custom
implementation. ";
+ }
+ msg = msg + "Help can be found
@http://jakarta.apache.org/commons/logging/troubleshooting.html.";;
+
if (isDiagnosticsEnabled()) {
logDiagnostic(msg);
}
@@ -1171,6 +1187,70 @@
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>Class</code> is assignable from the
+ */
+ 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
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