1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.logging.log4j.core;
18
19 import java.io.Serializable;
20 import java.util.Map;
21
22 import org.apache.logging.log4j.core.layout.ByteBufferDestination;
23 import org.apache.logging.log4j.core.layout.Encoder;
24
25 /**
26 * Lays out a {@linkplain LogEvent} in different formats.
27 *
28 * The formats are:
29 * <ul>
30 * <li>
31 * {@code byte[]}</li>
32 * <li>
33 * an implementer of {@linkplain Serializable}, like {@code byte[]}</li>
34 * <li>
35 * {@linkplain String}</li>
36 * <li>
37 * {@linkplain LogEvent}</li>
38 * </ul>
39 * <p>
40 * Since 2.6, Layouts can {@linkplain Encoder#encode(Object, ByteBufferDestination) encode} a {@code LogEvent} directly
41 * to a {@link ByteBufferDestination} without creating temporary intermediary objects.
42 * </p>
43 *
44 * @param <T>
45 * The {@link Serializable} type returned by {@link #toSerializable(LogEvent)}
46 */
47 public interface Layout<T extends Serializable> extends Encoder<LogEvent> {
48
49 /**
50 * Main {@linkplain org.apache.logging.log4j.core.config.plugins.Plugin#elementType() plugin element type} for
51 * Layout plugins.
52 *
53 * @since 2.1
54 */
55 String ELEMENT_TYPE = "layout";
56
57 /**
58 * Returns the format for the layout format.
59 * @return The footer.
60 */
61 byte[] getFooter();
62
63 /**
64 * Returns the header for the layout format.
65 * @return The header.
66 */
67 byte[] getHeader();
68
69 /**
70 * Formats the event suitable for display.
71 *
72 * @param event The Logging Event.
73 * @return The formatted event.
74 */
75 byte[] toByteArray(LogEvent event);
76
77 /**
78 * Formats the event as an Object that can be serialized.
79 *
80 * @param event The Logging Event.
81 * @return The formatted event.
82 */
83 T toSerializable(LogEvent event);
84
85 /**
86 * Returns the content type output by this layout. The base class returns "text/plain".
87 *
88 * @return the content type.
89 */
90 String getContentType();
91
92 /**
93 * Returns a description of the content format.
94 *
95 * @return a Map of key/value pairs describing the Layout-specific content format, or an empty Map if no content
96 * format descriptors are specified.
97 */
98 Map<String, String> getContentFormat();
99 }