/*
 * 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.commons.logging;

A simple logging interface abstracting logging APIs. In order to be instantiated successfully by LogFactory, classes that implement this interface must have a constructor that takes a single String parameter representing the "name" of this Log. 

The six logging levels used by Log are (in order):

trace (the least serious)
debug
info
warn
error
fatal (the most serious)

The mapping of these log levels to the concepts used by the underlying
logging system is implementation dependent.
The implementation should ensure, though, that this ordering behaves
as expected.

Performance is often a logging concern.
By examining the appropriate property,
a component can avoid expensive operations (producing information
to be logged).

For example,
   if (log.isDebugEnabled()) {
       ... do something expensive ...
       log.debug(theResult);
   }


Configuration of the underlying logging system will generally be done
external to the Logging APIs, through whatever mechanism is supported by
that system.
Version:
$Id: Log.java 1606045 2014-06-27 12:11:56Z tn $/**
 * A simple logging interface abstracting logging APIs.  In order to be
 * instantiated successfully by {@link LogFactory}, classes that implement
 * this interface must have a constructor that takes a single String
 * parameter representing the "name" of this Log.
 * <p>
 * The six logging levels used by <code>Log</code> are (in order):
 * <ol>
 * <li>trace (the least serious)</li>
 * <li>debug</li>
 * <li>info</li>
 * <li>warn</li>
 * <li>error</li>
 * <li>fatal (the most serious)</li>
 * </ol>
 * The mapping of these log levels to the concepts used by the underlying
 * logging system is implementation dependent.
 * The implementation should ensure, though, that this ordering behaves
 * as expected.
 * <p>
 * Performance is often a logging concern.
 * By examining the appropriate property,
 * a component can avoid expensive operations (producing information
 * to be logged).
 * <p>
 * For example,
 * <pre>
 *    if (log.isDebugEnabled()) {
 *        ... do something expensive ...
 *        log.debug(theResult);
 *    }
 * </pre>
 * <p>
 * Configuration of the underlying logging system will generally be done
 * external to the Logging APIs, through whatever mechanism is supported by
 * that system.
 *
 * @version $Id: Log.java 1606045 2014-06-27 12:11:56Z tn $
 */
public interface Log {

    
Logs a message with debug log level.
Params:
message – log this message/**
     * Logs a message with debug log level.
     *
     * @param message log this message
     */
    void debug(Object message);

    
Logs an error with debug log level.
Params:
message – log this message
t – log this cause/**
     * Logs an error with debug log level.
     *
     * @param message log this message
     * @param t log this cause
     */
    void debug(Object message, Throwable t);

    
Logs a message with error log level.
Params:
message – log this message/**
     * Logs a message with error log level.
     *
     * @param message log this message
     */
    void error(Object message);

    
Logs an error with error log level.
Params:
message – log this message
t – log this cause/**
     * Logs an error with error log level.
     *
     * @param message log this message
     * @param t log this cause
     */
    void error(Object message, Throwable t);

    
Logs a message with fatal log level.
Params:
message – log this message/**
     * Logs a message with fatal log level.
     *
     * @param message log this message
     */
    void fatal(Object message);

    
Logs an error with fatal log level.
Params:
message – log this message
t – log this cause/**
     * Logs an error with fatal log level.
     *
     * @param message log this message
     * @param t log this cause
     */
    void fatal(Object message, Throwable t);

    
Logs a message with info log level.
Params:
message – log this message/**
     * Logs a message with info log level.
     *
     * @param message log this message
     */
    void info(Object message);

    
Logs an error with info log level.
Params:
message – log this message
t – log this cause/**
     * Logs an error with info log level.
     *
     * @param message log this message
     * @param t log this cause
     */
    void info(Object message, Throwable t);

    
Is debug logging currently enabled?

Call this method to prevent having to perform expensive operations
(for example, String concatenation)
when the log level is more than debug.
Returns:
true if debug is enabled in the underlying logger./**
     * Is debug logging currently enabled?
     * <p>
     * Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than debug.
     *
     * @return true if debug is enabled in the underlying logger.
     */
    boolean isDebugEnabled();

    
Is error logging currently enabled?

Call this method to prevent having to perform expensive operations
(for example, String concatenation)
when the log level is more than error.
Returns:
true if error is enabled in the underlying logger./**
     * Is error logging currently enabled?
     * <p>
     * Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than error.
     *
     * @return true if error is enabled in the underlying logger.
     */
    boolean isErrorEnabled();

    
Is fatal logging currently enabled?

Call this method to prevent having to perform expensive operations
(for example, String concatenation)
when the log level is more than fatal.
Returns:
true if fatal is enabled in the underlying logger./**
     * Is fatal logging currently enabled?
     * <p>
     * Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than fatal.
     *
     * @return true if fatal is enabled in the underlying logger.
     */
    boolean isFatalEnabled();

    
Is info logging currently enabled?

Call this method to prevent having to perform expensive operations
(for example, String concatenation)
when the log level is more than info.
Returns:
true if info is enabled in the underlying logger./**
     * Is info logging currently enabled?
     * <p>
     * Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than info.
     *
     * @return true if info is enabled in the underlying logger.
     */
    boolean isInfoEnabled();

    
Is trace logging currently enabled?

Call this method to prevent having to perform expensive operations
(for example, String concatenation)
when the log level is more than trace.
Returns:
true if trace is enabled in the underlying logger./**
     * Is trace logging currently enabled?
     * <p>
     * Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than trace.
     *
     * @return true if trace is enabled in the underlying logger.
     */
    boolean isTraceEnabled();

    
Is warn logging currently enabled?

Call this method to prevent having to perform expensive operations
(for example, String concatenation)
when the log level is more than warn.
Returns:
true if warn is enabled in the underlying logger./**
     * Is warn logging currently enabled?
     * <p>
     * Call this method to prevent having to perform expensive operations
     * (for example, <code>String</code> concatenation)
     * when the log level is more than warn.
     *
     * @return true if warn is enabled in the underlying logger.
     */
    boolean isWarnEnabled();

    
Logs a message with trace log level.
Params:
message – log this message/**
     * Logs a message with trace log level.
     *
     * @param message log this message
     */
    void trace(Object message);

    
Logs an error with trace log level.
Params:
message – log this message
t – log this cause/**
     * Logs an error with trace log level.
     *
     * @param message log this message
     * @param t log this cause
     */
    void trace(Object message, Throwable t);

    
Logs a message with warn log level.
Params:
message – log this message/**
     * Logs a message with warn log level.
     *
     * @param message log this message
     */
    void warn(Object message);

    
Logs an error with warn log level.
Params:
message – log this message
t – log this cause/**
     * Logs an error with warn log level.
     *
     * @param message log this message
     * @param t log this cause
     */
    void warn(Object message, Throwable t);
}