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/*
* 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.message;
import java.io.Serializable;
import org.apache.logging.log4j.util.StringBuilderFormattable;
/**
* An interface for various Message implementations that can be logged. Messages can act as wrappers
* around Objects so that user can have control over converting Objects to Strings when necessary without
* requiring complicated formatters and as a way to manipulate the message based on information available
* at runtime such as the locale of the system.
*
* Custom Message implementations should consider implementing the {@link StringBuilderFormattable}
* interface for more efficient processing. Garbage-free Layouts will call
* {@link StringBuilderFormattable#formatTo(StringBuilder) formatTo(StringBuilder)} instead of
* {@link Message#getFormattedMessage()} if the Message implements StringBuilderFormattable.
*
*
* Note: Message objects should not be considered to be thread safe nor should they be assumed to be
* safely reusable even on the same thread. The logging system may provide information to the Message
* objects and the Messages might be queued for asynchronous delivery. Thus, any modifications to a
* Message object by an application should by avoided after the Message has been passed as a parameter on
* a Logger method.
*
*
* @see StringBuilderFormattable
*/
/*
* Implementation note: this interface extends Serializable since LogEvents must be serializable.
*/
public interface Message extends Serializable {
/**
* Gets the Message formatted as a String. Each Message implementation determines the
* appropriate way to format the data encapsulated in the Message. Messages that provide
* more than one way of formatting the Message will implement MultiformatMessage.
*
* When configured to log asynchronously, this method is called before the Message is queued, unless this
* message implements {@link ReusableMessage} or is annotated with {@link AsynchronouslyFormattable}.
* This gives the Message implementation class a chance to create a formatted message String with the current value
* of any mutable objects.
* The intention is that the Message implementation caches this formatted message and returns it on subsequent
* calls. (See LOG4J2-763.)
*
*
* When logging synchronously, this method will not be called for Messages that implement the
* {@link StringBuilderFormattable} interface: instead, the
* {@link StringBuilderFormattable#formatTo(StringBuilder) formatTo(StringBuilder)} method will be called so the
* Message can format its contents without creating intermediate String objects.
*
*
* @return The message String.
*/
String getFormattedMessage();
/**
* Gets the format portion of the Message.
*
* @return The message format. Some implementations, such as ParameterizedMessage, will use this as
* the message "pattern". Other Messages may simply return an empty String.
* TODO Do all messages have a format? What syntax? Using a Formatter object could be cleaner.
* (RG) In SimpleMessage the format is identical to the formatted message. In ParameterizedMessage and
* StructuredDataMessage it is not. It is up to the Message implementer to determine what this
* method will return. A Formatter is inappropriate as this is very specific to the Message
* implementation so it isn't clear to me how having a Formatter separate from the Message would be cleaner.
*/
String getFormat();
/**
* Gets parameter values, if any.
*
* @return An array of parameter values or null.
*/
Object[] getParameters();
/**
* Gets the throwable, if any.
*
* @return the throwable or null.
*/
Throwable getThrowable();
}