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
21 /**
22 * Lays out a {@linkplain LogEvent} in different formats.
23 * The formats are: byte[], or an implementor of {@linkplain Serializable}, like {@code byte[]},
24 * String, and LogEvent.
25 *
26 * @doubt There is still a need for a character-based layout for character based event sinks (databases, etc). Would introduce an
27 * EventEncoder, EventRenderer or something similar for the logging event to byte encoding. (RG) A layout can be configured with a
28 * Charset and then Strings can be converted to byte arrays. OTOH, it isn't possible to write byte arrays as character streams.
29 * @param <T>
30 * The Object type that will be returned on the {@link #toSerializable(LogEvent)} call.
31 */
32 public interface Layout<T extends Serializable> {
33 /**
34 * Returns the format for the layout format.
35 * @return The footer.
36 * @doubt the concept of header and footer is not universal, should not be on the base interface.
37 * (RG) I agree with this.
38 */
39 byte[] getFooter();
40
41 /**
42 * Returns the header for the layout format.
43 * @return The header.
44 * @doubt the concept of header and footer is not universal, should not be on the base interface.
45 * (RG) I agree with this.
46 */
47 byte[] getHeader();
48
49 /**
50 * Formats the event suitable for display.
51 *
52 * @param event The Logging Event.
53 * @return The formatted event.
54 * @doubt Likely better to write to a OutputStream instead of return a byte[]. (RG) That limits how the
55 * Appender can use the Layout. For example, it might concatenate information in front or behind the
56 * data and then write it all to the OutputStream in one call.
57 */
58 byte[] toByteArray(LogEvent event);
59
60 /**
61 * Formats the event as an Object that can be serialized.
62 *
63 * @param event The Logging Event.
64 * @return The formatted event.
65 */
66 T toSerializable(LogEvent event);
67
68
69 }