/*
 * 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.juli.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.
Author:
Scott Sanders, Rod Waldhoff/**
 * <p>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>
 *
 * <p> The six logging levels used by <code>Log</code> are (in order):</p>
 * <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>
 * <p>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>
 *
 * <p>Performance is often a logging concern.
 * By examining the appropriate property,
 * a component can avoid expensive operations (producing information
 * to be logged).</p>
 *
 * <p> For example,
 * <code>
 *    if (log.isDebugEnabled()) {
 *        ... do something expensive ...
 *        log.debug(theResult);
 *    }
 * </code>
 * </p>
 *
 * <p>Configuration of the underlying logging system will generally be done
 * external to the Logging APIs, through whatever mechanism is supported by
 * that system.</p>
 *
 * @author <a href="mailto:sanders@apache.org">Scott Sanders</a>
 * @author Rod Waldhoff
 */
public interface Log {


    // ----------------------------------------------------- Logging Properties


    
 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 level logging is enabled, otherwise
        false/**
     * <p> Is debug logging currently enabled? </p>
     *
     * <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. </p>
     *
     * @return <code>true</code> if debug level logging is enabled, otherwise
     *         <code>false</code>
     */
    public 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 level logging is enabled, otherwise
        false/**
     * <p> Is error logging currently enabled? </p>
     *
     * <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. </p>
     *
     * @return <code>true</code> if error level logging is enabled, otherwise
     *         <code>false</code>
     */
    public 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 level logging is enabled, otherwise
        false/**
     * <p> Is fatal logging currently enabled? </p>
     *
     * <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. </p>
     *
     * @return <code>true</code> if fatal level logging is enabled, otherwise
     *         <code>false</code>
     */
    public 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 level logging is enabled, otherwise
        false/**
     * <p> Is info logging currently enabled? </p>
     *
     * <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. </p>
     *
     * @return <code>true</code> if info level logging is enabled, otherwise
     *         <code>false</code>
     */
    public 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 level logging is enabled, otherwise
        false/**
     * <p> Is trace logging currently enabled? </p>
     *
     * <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. </p>
     *
     * @return <code>true</code> if trace level logging is enabled, otherwise
     *         <code>false</code>
     */
    public 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 level logging is enabled, otherwise
        false/**
     * <p> Is warn logging currently enabled? </p>
     *
     * <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. </p>
     *
     * @return <code>true</code> if warn level logging is enabled, otherwise
     *         <code>false</code>
     */
    public boolean isWarnEnabled();


    // -------------------------------------------------------- Logging Methods


    
 Log a message with trace log level. 
Params:
message – log this message/**
     * <p> Log a message with trace log level. </p>
     *
     * @param message log this message
     */
    public void trace(Object message);


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


    
 Log a message with debug log level. 
Params:
message – log this message/**
     * <p> Log a message with debug log level. </p>
     *
     * @param message log this message
     */
    public void debug(Object message);


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


    
 Log a message with info log level. 
Params:
message – log this message/**
     * <p> Log a message with info log level. </p>
     *
     * @param message log this message
     */
    public void info(Object message);


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


    
 Log a message with warn log level. 
Params:
message – log this message/**
     * <p> Log a message with warn log level. </p>
     *
     * @param message log this message
     */
    public void warn(Object message);


    
 Log an error with warn log level. 
Params:
message – log this message
t – log this cause/**
     * <p> Log an error with warn log level. </p>
     *
     * @param message log this message
     * @param t log this cause
     */
    public void warn(Object message, Throwable t);


    
 Log a message with error log level. 
Params:
message – log this message/**
     * <p> Log a message with error log level. </p>
     *
     * @param message log this message
     */
    public void error(Object message);


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


    
 Log a message with fatal log level. 
Params:
message – log this message/**
     * <p> Log a message with fatal log level. </p>
     *
     * @param message log this message
     */
    public void fatal(Object message);


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


}