com.dua3.utility.logging.log4j.LogAppenderLog4j Maven / Gradle / Ivy
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package com.dua3.utility.logging.log4j;
import org.jspecify.annotations.Nullable;
import com.dua3.utility.logging.LogEntryDispatcher;
import com.dua3.utility.logging.LogEntryFilter;
import com.dua3.utility.logging.LogEntryHandler;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;
import org.apache.logging.log4j.core.config.Property;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.layout.PatternLayout;
import java.io.Serializable;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
/**
* This class is an implementation of the Log4j Appender and LogEntryHandlerPool interfaces.
* It is used as an appender for log events and provides a mechanism for forwarding log4j log events to applications.
*/
public class LogAppenderLog4j extends AbstractAppender {
/**
* The name of the appender class used in the log4j configuration.
*
*
* This variable holds the simple name of the log4j appender class used in the application's log4j configuration.
*
*/
public static final String APPENDER_NAME = LogAppenderLog4j.class.getSimpleName();
/**
* The list of handlers for log entries.
*/
private final List> handlers = new ArrayList<>();
/**
* The LogEntryDispatcher associated with this LogAppenderLog4j instance.
* The LogEntryDispatcher is responsible for dispatching log entries to registered handlers based on a filter.
*/
private final LogEntryDispatcherLog4J dispatcher;
/**
* This class represents an implementation of the LogEntryDispatcher interface using Log4J.
* It dispatches log entries to registered handlers based on a filter.
*/
public class LogEntryDispatcherLog4J implements LogEntryDispatcher {
private volatile LogEntryFilter filter = LogEntryFilter.ALL_PASS_FILTER;
@Override
public void addLogEntryHandler(LogEntryHandler handler) {
handlers.add(new WeakReference<>(handler));
}
@Override
public void removeLogEntryHandler(LogEntryHandler handler) {
handlers.removeIf(h -> h.get() == handler);
}
@Override
public void setFilter(LogEntryFilter filter) {
this.filter = filter;
}
@Override
public LogEntryFilter getFilter() {
return filter;
}
@Override
public Collection getLogEntryHandlers() {
return handlers.stream().map(WeakReference::get).filter(Objects::nonNull).toList();
}
/**
* Returns the LogAppenderLog4j instance associated with this LogEntryDispatcherLog4J instance.
*
* @return the LogAppenderLog4j instance
*/
public LogAppenderLog4j getAppender() {
return LogAppenderLog4j.this;
}
}
/**
* Constructs a new instance of LogAppenderLog4j with the specified parameters.
*
* @param name the name of the appender
* @param filter the filter to be used for filtering log events (nullable)
* @param layout the layout to be used for formatting log events (nullable)
* @param ignoreExceptions specifies whether exceptions should be ignored or not
*/
protected LogAppenderLog4j(String name, @Nullable Filter filter, @Nullable Layout layout,
final boolean ignoreExceptions) {
super(name, filter, layout, ignoreExceptions, Property.EMPTY_ARRAY);
this.dispatcher = new LogEntryDispatcherLog4J();
}
/**
* Creates a LogAppenderLog4j object with the specified parameters.
*
* @param name the name of the appender
* @param ignoreExceptions whether to ignore exceptions thrown by the appender
* @param layout the layout for formatting log messages
* @param filter the filter for filtering log events
* @return a LogAppenderLog4j object
*/
@PluginFactory
public static LogAppenderLog4j createAppender(
@PluginAttribute("name") @Nullable String name,
@PluginAttribute("ignoreExceptions") boolean ignoreExceptions,
@PluginElement("Layout") @Nullable Layout layout,
@PluginElement("Filters") @Nullable Filter filter) {
if (name == null) {
LOGGER.warn("No name provided for {}", APPENDER_NAME);
name = "[unnamed]";
}
if (layout == null) {
layout = PatternLayout.createDefaultLayout();
}
return new LogAppenderLog4j(name, filter, layout, ignoreExceptions);
}
/**
* Dispatches a log event to the list of log entry handlers.
*
* This method iterates over the list of log entry handlers and invokes the `handleEntry` method
* on each not garbage collected handler.
*
* If any garbage collected log entry handler is detected, the log entry list is cleaned up.
*
* @param event the log event to be appended
*/
@Override
public void append(LogEvent event) {
LogEntryLog4J entry = new LogEntryLog4J(event);
boolean pass = dispatcher.filter.test(entry);
Iterator> iterator = handlers.iterator();
while (iterator.hasNext()) {
LogEntryHandler handler = iterator.next().get();
if (handler == null) {
iterator.remove();
} else if (pass) {
handler.handleEntry(entry);
}
}
}
@Override
public void start() {
super.start();
}
/**
* Returns the LogEntryDispatcher associated with the LogAppenderLog4j instance.
*
* @return the LogEntryDispatcher
*/
public LogEntryDispatcherLog4J dispatcher() {
return dispatcher;
}
}