001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements. See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache license, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License. You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the license for the specific language governing permissions and
015     * limitations under the license.
016     */
017    package org.apache.log4j;
018    
019    import org.apache.log4j.spi.Filter;
020    import org.apache.log4j.spi.ErrorHandler;
021    import org.apache.log4j.spi.LoggingEvent;
022    
023    /**
024     * Implement this interface for your own strategies for outputting log
025     * statements.
026     *
027     * @author Ceki Gülcü
028     */
029    public interface Appender {
030    
031        /**
032         * Add a filter to the end of the filter list.
033         * @param newFilter The filter to add.
034         *
035         * @since 0.9.0
036         */
037        void addFilter(Filter newFilter);
038    
039        /**
040         * Returns the head Filter. The Filters are organized in a linked list
041         * and so all Filters on this Appender are available through the result.
042         *
043         * @return the head Filter or null, if no Filters are present
044         * @since 1.1
045         */
046        Filter getFilter();
047    
048        /**
049         * Clear the list of filters by removing all the filters in it.
050         *
051         * @since 0.9.0
052         */
053        void clearFilters();
054    
055        /**
056         * Release any resources allocated within the appender such as file
057         * handles, network connections, etc.
058         * <p/>
059         * <p>It is a programming error to append to a closed appender.
060         *
061         * @since 0.8.4
062         */
063        void close();
064    
065        /**
066         * Log in <code>Appender</code> specific way. When appropriate,
067         * Loggers will call the <code>doAppend</code> method of appender
068         * implementations in order to log.
069         * @param event The LoggingEvent.
070         */
071        void doAppend(LoggingEvent event);
072    
073    
074        /**
075         * Get the name of this appender.
076         *
077         * @return name, may be null.
078         */
079        String getName();
080    
081    
082        /**
083         * Set the {@link ErrorHandler} for this appender.
084         * @param errorHandler The error handler.
085         *
086         * @since 0.9.0
087         */
088        void setErrorHandler(ErrorHandler errorHandler);
089    
090        /**
091         * Returns the {@link ErrorHandler} for this appender.
092         * @return The error handler.
093         *
094         * @since 1.1
095         */
096        ErrorHandler getErrorHandler();
097    
098        /**
099         * Set the {@link Layout} for this appender.
100         * @param layout The Layout.
101         *
102         * @since 0.8.1
103         */
104        void setLayout(Layout layout);
105    
106        /**
107         * Returns this appenders layout.
108         * @return the Layout.
109         *
110         * @since 1.1
111         */
112        Layout getLayout();
113    
114    
115        /**
116         * Set the name of this appender. The name is used by other
117         * components to identify this appender.
118         * @param name The appender name.
119         *
120         * @since 0.8.1
121         */
122        void setName(String name);
123    
124        /**
125         * Configurators call this method to determine if the appender
126         * requires a layout. If this method returns {@code true},
127         * meaning that layout is required, then the configurator will
128         * configure an layout using the configuration information at its
129         * disposal.  If this method returns {@code false}, meaning that
130         * a layout is not required, then layout configuration will be
131         * skipped even if there is available layout configuration
132         * information at the disposal of the configurator..
133         * <p/>
134         * <p>In the rather exceptional case, where the appender
135         * implementation admits a layout but can also work without it, then
136         * the appender should return {@code true}.
137         * @return true if a Layout is required.
138         *
139         * @since 0.8.4
140         */
141        boolean requiresLayout();
142    }
143