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.message;
18
19 import java.io.Serializable;
20
21 /**
22 * An interface for various Message implementations that can be logged. Messages can act as wrappers
23 * around Objects so that user can have control over converting Objects to Strings when necessary without
24 * requiring complicated formatters and as a way to manipulate the message based on information available
25 * at runtime such as the locale of the system.
26 *<p>
27 * Note: Message objects should not be considered to be thread safe nor should they be assumed to be
28 * safely reusable even on the same thread. The logging system may provide information to the Message
29 * objects and the Messages might be queued for asynchronous delivery. Thus, any modifications to a
30 * Message object by an application should by avoided after the Message has been passed as a parameter on
31 * a Logger method.
32 * </p>
33 * TODO Interfaces should rarely extend Serializable according to Effective Java 2nd Ed pg 291.
34 * (RG) That section also says "If a class or interface exists primarily to participate in a framework that
35 * requires all participants to implement Serializable, then it makes perfect sense for the class or
36 * interface to implement or extend Serializable". Such is the case here as the LogEvent must be Serializable.
37 */
38 public interface Message extends Serializable {
39
40 /**
41 * Gets the Message formatted as a String. Each Message implementation determines the
42 * appropriate way to format the data encapsulated in the Message. Messages that provide
43 * more than one way of formatting the Message will implement MultiformatMessage.
44 *
45 * @return The message String.
46 */
47 String getFormattedMessage();
48
49 /**
50 * Gets the format portion of the Message.
51 *
52 * @return The message format. Some implementations, such as ParameterizedMessage, will use this as
53 * the message "pattern". Other Messages may simply return an empty String.
54 * TODO Do all messages have a format? What syntax? Using a Formatter object could be cleaner.
55 * (RG) In SimpleMessage the format is identical to the formatted message. In ParameterizedMessage and
56 * StructuredDataMessage it is not. It is up to the Message implementer to determine what this
57 * method will return. A Formatter is inappropriate as this is very specific to the Message
58 * implementation so it isn't clear to me how having a Formatter separate from the Message would be cleaner.
59 */
60 String getFormat();
61
62 /**
63 * Gets parameter values, if any.
64 *
65 * @return An array of parameter values or null.
66 */
67 Object[] getParameters();
68
69 /**
70 * Gets the throwable, if any.
71 *
72 * @return the throwable or null.
73 */
74 Throwable getThrowable();
75 }