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/*
 * Copyright 2001-2004 The Apache Software Foundation.
 * 
 * Licensed 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 {@link 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): *

    *
  1. trace (the least serious)
  2. *
  3. debug
  4. *
  5. info
  6. *
  7. warn
  8. *
  9. error
  10. *
  11. fatal (the most serious)
  12. *
* The mapping of these log levels to the concepts used by the underlying * logging system is implementation dependent. * The implemention 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 * @author Rod Waldhoff * @version $Id: Log.java,v 1.19 2004/06/06 21:16:04 rdonkin Exp $ */ 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.

*/ 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.

*/ 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.

*/ 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.

*/ 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.

*/ 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.

*/ public boolean isWarnEnabled(); // -------------------------------------------------------- Logging Methods /** *

Log a message with trace log level.

* * @param message log this message */ public void trace(Object message); /** *

Log an error with trace log level.

* * @param message log this message * @param t log this cause */ public void trace(Object message, Throwable t); /** *

Log a message with debug log level.

* * @param message log this message */ public void debug(Object message); /** *

Log an error with debug log level.

* * @param message log this message * @param t log this cause */ public void debug(Object message, Throwable t); /** *

Log a message with info log level.

* * @param message log this message */ public void info(Object message); /** *

Log an error with info log level.

* * @param message log this message * @param t log this cause */ public void info(Object message, Throwable t); /** *

Log a message with warn log level.

* * @param message log this message */ public void warn(Object message); /** *

Log an error with warn log level.

* * @param message log this message * @param t log this cause */ public void warn(Object message, Throwable t); /** *

Log a message with error log level.

* * @param message log this message */ public void error(Object message); /** *

Log an error with error log level.

* * @param message log this message * @param t log this cause */ public void error(Object message, Throwable t); /** *

Log a message with fatal log level.

* * @param message log this message */ public void fatal(Object message); /** *

Log an error with fatal log level.

* * @param message log this message * @param t log this cause */ public void fatal(Object message, Throwable t); }


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