ppkarwasz commented on code in PR #2374:
URL: https://github.com/apache/logging-log4j2/pull/2374#discussion_r1527193084
##########
log4j-api/src/main/java/org/apache/logging/log4j/spi/Provider.java:
##########
@@ -97,127 +217,266 @@ public String getVersions() {
/**
* Gets the priority (natural ordering) of this Provider.
- *
+ * <p>
+ * Log4j selects the highest priority provider.
+ * </p>
* @return the priority of this Provider
*/
public Integer getPriority() {
return priority;
}
/**
- * Gets the class name of the {@link
org.apache.logging.log4j.spi.LoggerContextFactory} implementation of this
- * Provider.
+ * Gets the class name of the {@link LoggerContextFactory} implementation
of this Provider.
*
- * @return the class name of a LoggerContextFactory implementation
+ * @return the class name of a LoggerContextFactory implementation or
{@code null} if unspecified.
+ * @see #loadLoggerContextFactory()
*/
public String getClassName() {
- if (loggerContextFactoryClass != null) {
- return loggerContextFactoryClass.getName();
- }
- return className;
+ return loggerContextFactoryClass != null ?
loggerContextFactoryClass.getName() : className;
}
/**
- * Loads the {@link org.apache.logging.log4j.spi.LoggerContextFactory}
class specified by this Provider.
+ * Loads the {@link LoggerContextFactory} class specified by this Provider.
*
- * @return the LoggerContextFactory implementation class or {@code null}
if there was an error loading it
+ * @return the LoggerContextFactory implementation class or {@code null}
if unspecified or a loader error occurred.
+ * @see #createLoggerContextFactory()
*/
public Class<? extends LoggerContextFactory> loadLoggerContextFactory() {
if (loggerContextFactoryClass != null) {
return loggerContextFactoryClass;
}
- if (className == null) {
- return null;
- }
+ final String className = getClassName();
final ClassLoader loader = classLoader.get();
- if (loader == null) {
+ // Support for deprecated {@code META-INF/log4j-provider.properties}
format.
+ // In the remaining cases {@code loader == null}.
+ if (loader == null || className == null) {
return null;
}
try {
final Class<?> clazz = loader.loadClass(className);
if (LoggerContextFactory.class.isAssignableFrom(clazz)) {
return clazz.asSubclass(LoggerContextFactory.class);
+ } else {
+ LOGGER.error(
+ "Class {} specified in {} does not extend {}",
+ className,
+ getUrl(),
+ LoggerContextFactory.class.getName());
}
} catch (final Exception e) {
- LOGGER.error("Unable to create class {} specified in {}",
className, url.toString(), e);
+ LOGGER.error("Unable to create class {} specified in {}",
className, getUrl(), e);
}
return null;
}
/**
- * Gets the class name of the {@link
org.apache.logging.log4j.spi.ThreadContextMap} implementation of this Provider.
- *
+ * Extension point for providers to create a {@link LoggerContextFactory}.
+ * @since 2.24.0
+ */
+ protected LoggerContextFactory createLoggerContextFactory() {
+ final Class<? extends LoggerContextFactory> factoryClass =
loadLoggerContextFactory();
+ if (factoryClass != null) {
+ try {
+ return LoaderUtil.newInstanceOf(factoryClass);
+ } catch (final Exception e) {
+ LOGGER.error(
+ "Unable to create instance of class {} specified in
{}", factoryClass.getName(), getUrl(), e);
+ }
+ }
+ LOGGER.warn("Falling back to {}", SimpleLoggerContextFactory.INSTANCE);
+ return SimpleLoggerContextFactory.INSTANCE;
+ }
+
+ /**
+ * @return A lazily initialized logger context factory
+ * @since 2.24.0
+ */
+ public final LoggerContextFactory getLoggerContextFactory() {
Review Comment:
I wanted to stress out the `LoggerContextFactory` is a singleton.
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