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Merge in the allow-flawed branch, as there were no objections.

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git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/logging/trunk@190565 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Simon Kitching
2005-06-14 10:03:48 +00:00
parent ca0188c41e
commit a3f8e5302a
4 changed files with 475 additions and 197 deletions
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567
src/java/org/apache/commons/logging/impl/LogFactoryImpl.java
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@@ -20,8 +20,6 @@ package org.apache.commons.logging.impl;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;
@@ -99,6 +97,49 @@ public class LogFactoryImpl extends LogFactory {
protected static final String LOG_PROPERTY_OLD =
"org.apache.commons.logging.log";
/**
* The name of the system property which can be set true/false to
* determine system behaviour when a bad context-classloader is encountered.
* When set to false
*
* Default behaviour: true (tolerates bad context classloaders)
*
* See also method setAttribute.
*/
public static final String ALLOW_FLAWED_CONTEXT_PROPERTY =
"org.apache.commons.logging.Log.allowFlawedContext";
/**
* The name of the system property which can be set true/false to
* determine system behaviour when a bad logging adapter class is
* encountered during logging discovery. When set to false, an
* exception will be thrown and the app will fail to start. When set
* to true, discovery will continue (though the user might end up
* with a different logging implementation than they expected).
*
* Default behaviour: true (tolerates bad logging adapters)
*
* See also method setAttribute.
*/
public static final String ALLOW_FLAWED_DISCOVERY_PROPERTY =
"org.apache.commons.logging.Log.allowFlawedDiscovery";
/**
* The name of the system property which can be set true/false to
* determine system behaviour when a logging adapter class is
* encountered which has bound to the wrong Log class implementation.
* When set to false, an exception will be thrown and the app will fail
* to start. When set to true, discovery will continue (though the user
* might end up with a different logging implementation than they expected).
*
* Default behaviour: true (tolerates bad Log class hierarchy)
*
* See also method setAttribute.
*/
public static final String ALLOW_FLAWED_HIERARCHY_PROPERTY =
"org.apache.commons.logging.Log.allowFlawedHierarchy";
// ----------------------------------------------------- Instance Variables
@@ -158,6 +199,21 @@ public class LogFactoryImpl extends LogFactory {
protected Class logMethodSignature[] =
{ LogFactory.class };
/**
* See getBaseClassLoader and initConfiguration.
*/
private boolean allowFlawedContext;
/**
* See handleFlawedDiscovery and initConfiguration.
*/
private boolean allowFlawedDiscovery;
/**
* See handleFlawedHierarchy and initConfiguration.
*/
private boolean allowFlawedHierarchy;
// --------------------------------------------------------- Public Methods
@@ -272,6 +328,21 @@ public class LogFactoryImpl extends LogFactory {
* Set the configuration attribute with the specified name. Calling
* this with a <code>null</code> value is equivalent to calling
* <code>removeAttribute(name)</code>.
* <p>
* This method can be used to set logging configuration programmatically
* rather than via system properties. It can also be used in code running
* within a container (such as a webapp) to configure behaviour on a
* per-component level instead of globally as system properties would do.
* To use this method instead of a system property, call
* <pre>
* LogFactory.getFactory().setAttribute(...)
* </pre>
* This must be done before the first Log object is created; configuration
* changes after that point will be ignored.
* <p>
* This method is also called automatically if LogFactory detects a
* commons-logging.properties file; every entry in that file is set
* automatically as an attribute here.
*
* @param name Name of the attribute to set
* @param value Value of the attribute to set, or <code>null</code>
@@ -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.
*
* <p>Exposing this method outside of
* <code>org.apache.commons.logging.LogFactoryImpl</code>
* will create a security violation:
* This method uses <code>AccessController.doPrivileged()</code>.
* </p>
*
* Load a class, try first the thread class loader, and
* if it fails use the loader that loaded this class.
*
* @param name fully qualified class name of the class to load
*
* @throws LinkageError if the linkage fails
* @throws ExceptionInInitializerError if the initialization provoked
* by this method fails
* @throws ClassNotFoundException if the class cannot be located
*/
private static Class loadClass( final String name )
throws ClassNotFoundException
{
Object result = AccessController.doPrivileged(
new PrivilegedAction() {
public Object run() {
ClassLoader threadCL = getContextClassLoader();
if (threadCL != null) {
try {
return threadCL.loadClass(name);
} catch( ClassNotFoundException ex ) {
// ignore
}
}
try {
return Class.forName( name );
} catch (ClassNotFoundException e) {
return e;
}
}
});
if (result instanceof Class)
return (Class)result;
throw (ClassNotFoundException)result;
}
/**
* Is <em>JDK 1.3 with Lumberjack</em> logging available?
*
@@ -575,6 +602,63 @@ public class LogFactoryImpl extends LogFactory {
return false;
}
}
/**
* Attempt to find an attribute (see method setAttribute) or a
* system property with the provided name and return its value.
* <p>
* The attributes associated with this object are checked before
* system properties in case someone has explicitly called setAttribute,
* or a configuration property has been set in a commons-logging.properties
* file.
*
* @return the value associated with the property, or null.
*/
private String getConfigurationValue(String property) {
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.
* <p>
* This method usually returns the context classloader. However if it
* is discovered that the classloader which loaded this class is a child
* of the context classloader <i>and</i> the allowFlawedContext option
* has been set then the classloader which loaded this class is returned
* instead.
* <p>
* The only time when the classloader which loaded this class is a
* descendant (rather than the same as or an ancestor of the context
* classloader) is when an app has created custom classloaders but
* failed to correctly set the context classloader. This is a bug in
* the calling application; however we provide the option for JCL to
* simply generate a warning rather than fail outright.
*
*/
private ClassLoader getBaseClassLoader() throws LogConfigurationException {
ClassLoader 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.
* <p>
* @param c1 is a classloader (including the null classloader)
* @param c2 is a classloader (including the null classloader)
*
* @return c1 if it has c2 as an ancestor, c2 if it has c1 as an ancestor,
* and null if neither is an ancestor of the other.
*/
private ClassLoader getLowestClassLoader(ClassLoader c1, ClassLoader c2) {
// TODO: use AccessController when dealing with classloaders here
if (c1 == null)
return c2;
if (c2 == null)
return c1;
ClassLoader current;
// scan c1's ancestors to find c2
current = c1;
while (current != null) {
if (current == c2)
return c1;
current = current.getParent();
}
// scan c2's ancestors to find c1
// 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 <code>LogConfigurationException</code> that wraps
* the passed <code>Throwable</code>.
*
* @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 <code>null</code>.
*
* @param logAdapterClass <code>Code</code> whose name is
* <code>logClassName</code>, or <code>null</code> 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.
* <p>
* 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 {
* </ol>
* <p>
* 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 <code>null</code>.
* @param badClassLoader is the classloader we loaded the problem class from,
* ie it is equivalent to badClass.getClassLoader().
*
* @param cause is the <code>Throwable</code> to wrap.
* @param badClass is a Class object with the desired name, but which
* does not implement Log correctly.
*
* @return <code>LogConfigurationException</code> that wraps
* <code>cause</code> 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());
}
}
}