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 * (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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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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 StringBuilderFormattable interface for more efficient processing. Garbage-free Layouts will call formatTo(StringBuilder) instead of 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 Also:
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.
 * <p>
 * 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.
 * </p>
 * <p>
 * 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.
 * </p>
 *
 * @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 ReusableMessage or is annotated with 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 StringBuilderFormattable interface: instead, the formatTo(StringBuilder) method will be called so the Message can format its contents without creating intermediate String objects. 
Returns:
The message String./**
     * 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.
     * <p>
     * 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 <a href="https://issues.apache.org/jira/browse/LOG4J2-763">LOG4J2-763</a>.)
     * </p>
     * <p>
     * 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.
     * </p>
     *
     * @return The message String.
     */
    String getFormattedMessage();

    
Gets the format portion of the Message.
Returns:
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./**
     * 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.
Returns:
An array of parameter values or null./**
     * Gets parameter values, if any.
     *
     * @return An array of parameter values or null.
     */
    Object[] getParameters();

    
Gets the throwable, if any.
Returns:
the throwable or null./**
     * Gets the throwable, if any.
     *
     * @return the throwable or null.
     */
    Throwable getThrowable();
}