org.apache.logging.log4j.core.Layout Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.logging.log4j.core;
import java.io.Serializable;
import java.util.Map;
/**
* Lays out a {@linkplain LogEvent} in different formats.
*
* The formats are:
*
* -
* {@code byte[]}
* -
* an implementer of {@linkplain Serializable}, like {@code byte[]}
* -
* {@linkplain String}
* -
* {@linkplain LogEvent}
*
*
* @param
* The {@link Serializable} type returned by {@link #toSerializable(LogEvent)}
*
* TODO There is still a need for a character-based layout for character based event sinks (databases, etc). Would
* introduce an EventEncoder, EventRenderer or something similar for the logging event to byte encoding. (RG) A layout
* can be configured with a Charset and then Strings can be converted to byte arrays. OTOH, it isn't possible to write
* byte arrays as character streams.
*/
public interface Layout {
/**
* Main plugin element type for Layout plugins.
*
* @since 2.1
*/
String ELEMENT_TYPE = "layout";
/**
* Returns the format for the layout format.
* @return The footer.
*/
byte[] getFooter();
/**
* Returns the header for the layout format.
* @return The header.
*/
byte[] getHeader();
/**
* Formats the event suitable for display.
*
* @param event The Logging Event.
* @return The formatted event.
* TODO Likely better to write to a OutputStream instead of return a byte[]. (RG) That limits how the
* Appender can use the Layout. For example, it might concatenate information in front or behind the
* data and then write it all to the OutputStream in one call.
*/
byte[] toByteArray(LogEvent event);
// TODO: it would be nice to provide ByteBuffers alongside the byte[]s
/**
* Formats the event as an Object that can be serialized.
*
* @param event The Logging Event.
* @return The formatted event.
*/
T toSerializable(LogEvent event);
/**
* Returns the content type output by this layout. The base class returns "text/plain".
*
* @return the content type.
*/
String getContentType();
/**
* Returns a description of the content format.
*
* @return a Map of key/value pairs describing the Layout-specific content format, or an empty Map if no content
* format descriptors are specified.
*/
Map getContentFormat();
}