Appender.java

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j;

import org.apache.log4j.spi.Filter;
import org.apache.log4j.spi.ErrorHandler;
import org.apache.log4j.spi.LoggingEvent;

/**
 * Implement this interface for your own strategies for outputting log
 * statements.
 *
 * @author Ceki Gülcü
 */
public interface Appender {

    /**
     * Add a filter to the end of the filter list.
     *
     * @since 0.9.0
     */
    void addFilter(Filter newFilter);

    /**
     * Returns the head Filter. The Filters are organized in a linked list
     * and so all Filters on this Appender are available through the result.
     *
     * @return the head Filter or null, if no Filters are present
     * @since 1.1
     */
    public Filter getFilter();

    /**
     * Clear the list of filters by removing all the filters in it.
     *
     * @since 0.9.0
     */
    public void clearFilters();

    /**
     * Release any resources allocated within the appender such as file
     * handles, network connections, etc.
     * <p/>
     * <p>It is a programming error to append to a closed appender.
     *
     * @since 0.8.4
     */
    public void close();

    /**
     * Log in <code>Appender</code> specific way. When appropriate,
     * Loggers will call the <code>doAppend</code> method of appender
     * implementations in order to log.
     */
    public void doAppend(LoggingEvent event);

    /**
     * Get the name of this appender. The name uniquely identifies the
     * appender.
     */
    public String getName();

    /**
     * Set the {@link ErrorHandler} for this appender.
     *
     * @since 0.9.0
     */
    public void setErrorHandler(ErrorHandler errorHandler);

    /**
     * Returns the {@link ErrorHandler} for this appender.
     *
     * @since 1.1
     */
    public ErrorHandler getErrorHandler();

    /**
     * Set the {@link Layout} for this appender.
     *
     * @since 0.8.1
     */
    public void setLayout(Layout layout);

    /**
     * Returns this appenders layout.
     *
     * @since 1.1
     */
    public Layout getLayout();

    /**
     * Set the name of this appender. The name is used by other
     * components to identify this appender.
     *
     * @since 0.8.1
     */
    public void setName(String name);

    /**
     * Configurators call this method to determine if the appender
     * requires a layout. If this method returns <code>true</code>,
     * meaning that layout is required, then the configurator will
     * configure an layout using the configuration information at its
     * disposal.  If this method returns <code>false</code>, meaning that
     * a layout is not required, then layout configuration will be
     * skipped even if there is available layout configuration
     * information at the disposal of the configurator.
     * <p/>
     * <p>In the rather exceptional case, where the appender
     * implementation admits a layout but can also work without it, then
     * the appender should return <code>true</code>.
     *
     * @since 0.8.4
     */
    public boolean requiresLayout();
}