Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, QOS.ch. All rights reserved.
This program and the accompanying materials are dual-licensed under
either the terms of the Eclipse Public License v1.0 as published by
the Eclipse Foundation
  or (per the licensee's choosing)
under the terms of the GNU Lesser General Public License version 2.1
as published by the Free Software Foundation.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core;

import java.util.List;

import ch.qos.logback.core.filter.Filter;
import ch.qos.logback.core.spi.ContextAwareBase;
import ch.qos.logback.core.spi.FilterAttachableImpl;
import ch.qos.logback.core.spi.FilterReply;
import ch.qos.logback.core.status.WarnStatus;

Similar to AppenderBase except that derived appenders need to handle 
thread synchronization on their own.
Author:
Ceki Gülcü, Ralph Goers/**
 * Similar to AppenderBase except that derived appenders need to handle 
 * thread synchronization on their own.
 * 
 * @author Ceki Gülcü
 * @author Ralph Goers
 */
abstract public class UnsynchronizedAppenderBase<E> extends ContextAwareBase implements Appender<E> {

    protected boolean started = false;

    // using a ThreadLocal instead of a boolean add 75 nanoseconds per
    // doAppend invocation. This is tolerable as doAppend takes at least a few microseconds
    // on a real appender
    
The guard prevents an appender from repeatedly calling its own doAppend
method.
/**
     * The guard prevents an appender from repeatedly calling its own doAppend
     * method.
     */
    private ThreadLocal<Boolean> guard = new ThreadLocal<Boolean>();

    
Appenders are named.
/**
     * Appenders are named.
     */
    protected String name;

    private FilterAttachableImpl<E> fai = new FilterAttachableImpl<E>();

    public String getName() {
        return name;
    }

    private int statusRepeatCount = 0;
    private int exceptionCount = 0;

    static final int ALLOWED_REPEATS = 3;

    public void doAppend(E eventObject) {
        // WARNING: The guard check MUST be the first statement in the
        // doAppend() method.

        // prevent re-entry.
        if (Boolean.TRUE.equals(guard.get())) {
            return;
        }

        try {
            guard.set(Boolean.TRUE);

            if (!this.started) {
                if (statusRepeatCount++ < ALLOWED_REPEATS) {
                    addStatus(new WarnStatus("Attempted to append to non started appender [" + name + "].", this));
                }
                return;
            }

            if (getFilterChainDecision(eventObject) == FilterReply.DENY) {
                return;
            }

            // ok, we now invoke derived class' implementation of append
            this.append(eventObject);

        } catch (Exception e) {
            if (exceptionCount++ < ALLOWED_REPEATS) {
                addError("Appender [" + name + "] failed to append.", e);
            }
        } finally {
            guard.set(Boolean.FALSE);
        }
    }

    abstract protected void append(E eventObject);

    
Set the name of this appender.
/**
     * Set the name of this appender.
     */
    public void setName(String name) {
        this.name = name;
    }

    public void start() {
        started = true;
    }

    public void stop() {
        started = false;
    }

    public boolean isStarted() {
        return started;
    }

    public String toString() {
        return this.getClass().getName() + "[" + name + "]";
    }

    public void addFilter(Filter<E> newFilter) {
        fai.addFilter(newFilter);
    }

    public void clearAllFilters() {
        fai.clearAllFilters();
    }

    public List<Filter<E>> getCopyOfAttachedFiltersList() {
        return fai.getCopyOfAttachedFiltersList();
    }

    public FilterReply getFilterChainDecision(E event) {
        return fai.getFilterChainDecision(event);
    }
}