Author: ceki Date: Thu Jul 27 22:47:17 2006 New Revision: 365 Modified: logback/classic/trunk/src/site/xdocTemplates/shortIntro.xml Log: - The introduction section and the architecture repeat the same text. (I did not have time to perform the clean up.) - Changed "source" style to use the 'white-space: pre;' style. It's much more convenient than having to format source code manually. - In the short manual, use the letter L instead of C in logger related rules. - removed 3 paragraphs discussing object rendering as this concept is not implemented in LB. - performed many indentation related changes. Modified: logback/classic/trunk/src/site/xdocTemplates/shortIntro.xml ============================================================================== --- logback/classic/trunk/src/site/xdocTemplates/shortIntro.xml (original) +++ logback/classic/trunk/src/site/xdocTemplates/shortIntro.xml Thu Jul 27 22:47:17 2006 @@ -10,9 +10,9 @@ <table> <tr> - <td> + <td valign="top" align="top"> <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/2.5/"> - <img alt="Creative Commons License" border="0" valign="top" + <img alt="Creative Commons License" border="0" valign="top" align="top" src="http://creativecommons.org/images/public/somerights20.png"/> </a> </td> @@ -108,7 +108,7 @@ messages are formatted and where they are reported. </p> <p> - The Loggers are defined in the classic module. On the other + Loggers are defined in the classic module. On the other hand, Appenders and Layouts are defined in the core module of logback. </p> @@ -141,17 +141,11 @@ </div> <p> - For example, the logger named - <code>"com.foo"</code> - is a parent of the logger named - <code>"com.foo.Bar"</code> - . Similarly, - <code>"java"</code> - is a parent of - <code>"java.util"</code> - and an ancestor of - <code>"java.util.Vector"</code> - . This naming scheme should be familiar to most developers. + For example, the logger named <code>"com.foo"</code> is a parent + of the logger named <code>"com.foo.Bar"</code> . Similarly, + <code>"java"</code> is a parent of <code>"java.util"</code> and + an ancestor of <code>"java.util.Vector"</code> . This naming + scheme should be familiar to most developers. </p> <p> The root logger resides at the top of the logger hierarchy. @@ -161,44 +155,36 @@ <li>it always exists,</li> <li>it cannot be retrieved by name.</li> </ol> - All other loggers are retrieved with the class static + + <p>All other loggers are retrieved with the class static LoggerFactory.getLogger method. This method takes the name of the desired logger as a parameter. Some of the basic methods in the Logger interface are listed below. - <div class="source"> - <p>package org.slf4j;</p> + </p> - <p>public interface Logger {</p> - <p> - // Creation and retrieval method: - <br /> - public static Logger getLogger(String name); - <br /> - </p> - <p> - // printing methods: - <br /> - public void debug(Object message); - <br /> - public void info(Object message); - <br /> - public void warn(Object message); - <br /> - public void error(Object message); - <br /> - public void fatal(Object message); - <br /> - </p> - <p>}</p> - </div> - <p> - Loggers may be assigned levels. The set of possible levels, - that is DEBUG, INFO, WARN, ERROR and FATAL are defined in - the org.apache.log4j.Level class. Although we do not - encourage you to do so, you may define your own levels by - sub-classing the Level class. A perhaps better approach will - be explained later on. + <div class="source">package org.slf4j; + +public interface Logger { + + // Creation and retrieval method: + public static Logger getLogger(String name); + + // printing methods: + public void debug(Object message); + public void info(Object message); + public void warn(Object message); + public void error(Object message); + public void fatal(Object message); +}</div> + + <p> + Loggers may be assigned levels. The set of possible levels, that + is DEBUG, INFO, WARN and ERROR are defined in the + org.apache.log4j.Level class. The level class cannot be + sub-classed as a much better approach exist in the form of + Marker objects. </p> + <p> If a given logger is not assigned a level, then it inherits one from its closest ancestor with an assigned level. More @@ -208,10 +194,10 @@ <div class="definition"> <div class="deftitle">Level Inheritance</div> <p> - The inherited level for a given logger C, is equal to - the first non-null level in the logger hierarchy, - starting at C and proceeding upwards in the hierarchy - towards the root logger. + The inherited level for a given logger <em>L</em>, is equal to + the first non-null level in the logger hierarchy, starting at + <em>L</em> and proceeding upwards in the hierarchy towards the + root logger. </p> </div> <p> @@ -426,22 +412,13 @@ </table> <p> - In example 4, the loggers - <code>root</code> - and - <code>X</code> - and are assigned the levels - <code>Proot</code> - and + In example 4, the loggers <code>root</code> and <code>X</code> + and are assigned the levels <code>Proot</code> and <code>Px</code> - respectively. The loggers - <code>X.Y</code> - and - <code>X.Y.Z</code> - inherits their level value from their nearest parent - <code>X</code> - having an assigned level. + respectively. The loggers <code>X.Y</code> and + <code>X.Y.Z</code> inherits their level value from their nearest + parent <code>X</code> having an assigned level. </p> <p> @@ -452,20 +429,16 @@ <p> By definition, the printing method determines the level of a - logging request. For example, if - <code>c</code> - is a logger instance, then the statement - <code>c.info("..")</code> - is a logging request of level INFO. + logging request. For example, if <code>c</code> is a logger + instance, then the statement <code>c.info("..")</code> is a + logging request of level INFO. </p> <p> - A logging request is said to be - <em>enabled</em> - if its level is higher than or equal to the level of its - logger. Otherwise, the request is said to be - <em>disabled</em> - . A logger without an assigned level will inherit one from - the hierarchy. This rule is summarized below. + A logging request is said to be <em>enabled</em> if its level is + higher than or equal to the level of its logger. Otherwise, the + request is said to be <em>disabled</em>. A logger without an + assigned level will inherit one from the hierarchy. This rule is + summarized below. </p> <div class="definition"> <div class="deftitle">Basic Selection Rule</div> @@ -491,74 +464,25 @@ </p> <p>Here is an example of this rule.</p> - <div class="source"> - <p> - // get a logger instance named "com.foo", with an - <span class="blue">INFO</span> - level. - <br /> - Logger logger = LoggerFactory.getLogger("com.foo"); - <br /> - </p> - <p> - Logger barlogger = - LoggerFactory.getLogger("com.foo.Bar"); - <br /> - </p> - <p> - // This request is enabled, because - <span class="green">WARN</span> - >= - <span class="blue">INFO</span> - . - <br /> - logger. - <span class="green">warn</span> - ("Low fuel level."); - <br /> - </p> - <p> - // This request is disabled, because - <span class="green">DEBUG</span> - < - <span class="blue">INFO</span> - . - <br /> - logger. - <span class="green">debug</span> - ("Starting search for nearest gas station."); - <br /> - </p> - <p> - // The logger instance barlogger, named "com.foo.Bar", - <br /> - // will inherit its level from the logger named - <br /> - // "com.foo" Thus, the following request is enabled - <br /> - // because - <span class="green">INFO</span> - >= - <span class="blue">INFO</span> - . - <br /> - barlogger. - <span class="green">info</span> - ("Located nearest gas station."); - <br /> - </p> - <p> - // This request is disabled, because - <span class="green">DEBUG</span> - < - <span class="blue">INFO</span> - . - <br /> - barlogger. - <span class="green">debug</span> - ("Exiting gas station search"); - <br /> - </p> + <div class="source">// get a logger instance named "com.foo", with an <span class="blue">INFO</span> level. + Logger logger = LoggerFactory.getLogger("com.foo"); + + Logger barlogger = LoggerFactory.getLogger("com.foo.Bar"); + + // This request is enabled, because <span class="green">WARN</span> >= <span class="blue">INFO</span> + logger.<span class="green">warn</span>("Low fuel level."); + + + // This request is disabled, because <span class="green">DEBUG</span> < <span class="blue">INFO</span>. + logger.<span class="green">debug</span>("Starting search for nearest gas station."); + // The logger instance barlogger, named "com.foo.Bar", + // will inherit its level from the logger named + // "com.foo" Thus, the following request is enabled + // because <span class="green">INFO</span> >= <span class="blue">INFO</span>. + barlogger.<span class="green">info</span>("Located nearest gas station."); + + // This request is disabled, because <span class="green">DEBUG</span> < <span class="blue">INFO</span>. + barlogger.<span class="green">debug</span>("Exiting gas station search"); </div> <p> @@ -567,29 +491,23 @@ method with the same name will always return a reference to the exact same logger object. </p> + <p>For example, in</p> - <div class="source"> - Logger x = LoggerFactory.getLogger("wombat"); - <br /> - Logger y = LoggerFactory.getLogger("wombat"); - </div> - <code>x</code> - and - <code>y</code> - refer to - <em>exactly</em> - the same logger object. + <div class="source">Logger x = LoggerFactory.getLogger("wombat"); +Logger y = LoggerFactory.getLogger("wombat");</div> + <p><code>x</code> and <code>y</code> refer to <em>exactly</em> the + same logger object. + </p> <p> - Thus, it is possible to configure a logger and then to - retrieve the same instance somewhere else in the code - without passing around references. In fundamental - contradiction to biological parenthood, where parents always - preceed their children, logback classic loggers can be - created and configured in any order. In particular, a - "parent" logger will find and link to its descendants even - if it is instantiated after them. + Thus, it is possible to configure a logger and then to retrieve + the same instance somewhere else in the code without passing + around references. In fundamental contradiction to biological + parenthood, where parents always preceed their children, logback + classic loggers can be created and configured in any order. In + particular, a "parent" logger will find and link to its + descendants even if it is instantiated after them. </p> <p> Configuration of the logback environment is typically done @@ -598,18 +516,16 @@ discussed shortly. </p> <p> - Logback makes it easy to name loggers by - <em>software component</em> - . This can be accomplished by statically instantiating a - logger in each class, with the logger name equal to the - fully qualified name of the class. This is a useful and - straightforward method of defining loggers. As the log - output bears the name of the generating logger, this naming - strategy makes it easy to identify the origin of a log - message. However, this is only one possible, albeit common, - strategy for naming loggers. Logback does not restrict the - possible set of loggers. The developer is free to name the - loggers as desired. + Logback makes it easy to name loggers by <em>software + component</em>. This can be accomplished by statically + instantiating a logger in each class, with the logger name equal + to the fully qualified name of the class. This is a useful and + straightforward method of defining loggers. As the log output + bears the name of the generating logger, this naming strategy + makes it easy to identify the origin of a log message. However, + this is only one possible, albeit common, strategy for naming + loggers. Logback does not restrict the possible set of + loggers. The developer is free to name the loggers as desired. </p> <p> Nevertheless, naming loggers after the class where they are @@ -619,65 +535,57 @@ <div class="section"> <h3>Appenders and Layouts</h3> </div> - <p> - The ability to selectively enable or disable logging - requests based on their logger is only part of the picture. - Log4j allows logging requests to print to multiple - destinations. In log4j speak, an output destination is - called an appender. Currently, appenders exist for the - console, files, GUI components, remote socket servers, JMS, - NT Event Loggers, and remote UNIX Syslog daemons. It is also - possible to log asynchronously. + + <p> The ability to selectively enable or disable logging requests + based on their logger is only part of the picture. Logback allows + logging requests to print to multiple destinations. In logback + speak, an output destination is called an appender. Currently, + appenders exist for the console, files, remote socket servers, + JMS, and remote UNIX Syslog daemons. It is also possible to log + asynchronously. </p> + <p>More than one appender can be attached to a logger.</p> <p> - The addAppender method adds an appender to a given logger. - Each enabled logging request for a given logger will be - forwarded to all the appenders in that logger as well as the - appenders higher in the hierarchy. In other words, appenders - are inherited additively from the logger hierarchy. For - example, if a console appender is added to the root logger, - then all enabled logging requests will at least print on the - console. If in addition a file appender is added to a - logger, say C, then enabled logging requests for C and C's - children will print on a file and on the console. It is - possible to override this default behavior so that appender - accumulation is no longer additive by setting the additivity - flag to false. + The addAppender method adds an appender to a given logger. Each + enabled logging request for a given logger will be forwarded to + all the appenders in that logger as well as the appenders higher + in the hierarchy. In other words, appenders are inherited + additively from the logger hierarchy. For example, if a console + appender is added to the root logger, then all enabled logging + requests will at least print on the console. If in addition a + file appender is added to a logger, say <em>L</em>, then enabled + logging requests for <em>L</em> and <em>L</em>'s children will + print on a file and on the console. It is possible to override + this default behavior so that appender accumulation is no longer + additive by setting the additivity flag to false. </p> + <p> The rules governing appender additivity are summarized below. </p> <div class="definition"> + <div class="deftitle">Appender Additivity</div> - <p> - The output of a log statement of logger - <em>C</em> - will go to all the appenders in - <em>C</em> - and its ancestors. This is the meaning of the term - "appender additivity". + + <p> + The output of a log statement of logger <em>L</em> will go to + all the appenders in <em>L</em> and its ancestors. This is the + meaning of the term "appender additivity". </p> - <p> - However, if an ancestor of logger - <em>C</em> - , say - <em>P</em> - , has the additivity flag set to false, then - <em>C</em> - 's output will be directed to all the appenders in - <em>C</em> - and it's ancestors upto and including - <em>P</em> - but not the appenders in any of the ancestors of - <em>P</em> - . + + <p> However, if an ancestor of logger <em>L</em> , say + <em>P</em>, has the additivity flag set to false, then + <em>L</em>'s output will be directed to all the appenders in + <em>L</em> and it's ancestors upto and including <em>P</em> but + not the appenders in any of the ancestors of <em>P</em> . </p> + <p> - Loggers have their additivity flag set to true by - default. + Loggers have their additivity flag set to true by default. </p> + </div> The table below shows an example: @@ -749,19 +657,17 @@ <p> - More often than not, users wish to customize not only the - output destination but also the output format. This is - accomplished by associating a - <em>layout</em> - with an appender. The layout is responsible for formatting - the logging request according to the user's wishes, whereas - an appender takes care of sending the formatted output to - its destination. The PatternLayout, part of the standard - log4j distribution, lets the user specify the output format - according to conversion patterns similar to the C language - <code>printf</code> - function. + More often than not, users wish to customize not only the output + destination but also the output format. This is accomplished by + associating a <em>layout</em> with an appender. The layout is + responsible for formatting the logging request according to the + user's wishes, whereas an appender takes care of sending the + formatted output to its destination. The PatternLayout, part of + the standard logback distribution, lets the user specify the + output format according to conversion patterns similar to the C + language <code>printf</code> function. </p> + <p> For example, the PatternLayout with the conversion pattern "%r [%t] %-5p %c - %m%n" will output something akin to: @@ -779,89 +685,50 @@ associated with the log request. The text after the '-' is the message of the statement. </p> - <p> - Just as importantly, log4j will render the content of the - log message according to user specified criteria. For - example, if you frequently need to log - <code>Oranges</code> - , an object type used in your current project, then you can - register an - <code>OrangeRenderer</code> - that will be invoked whenever an orange needs to be logged. - </p> - <p> - Object rendering follows the class hierarchy. For example, - assuming oranges are fruits, if you register an - <code>FruitRenderer</code> - , all fruits including oranges will be rendered by the - <code>FruitRenderer</code> - , unless of course you registered an orange specific - <code>OrangeRenderer</code> - . - </p> - <p> - Object renderers have to implement the ObjectRenderer - interface. - </p> <h4>More sophitsicated ways of logging</h4> <p> If you are a SLF4J user (if not, you should be...), you'll - notice that the methods used to request logging do not only - take a String as a parameter. Some methods allow more - sophisticated parameter configurations. + notice that the methods used to request logging do not only take + a String as a parameter. Some methods allow more sophisticated + parameter configurations. </p> - <p> - For some Logger - <code>logger</code> - , writing, - </p> + <p> For some Logger <code>logger</code>, writing, </p> + <div class="source"> - logger.debug("Entry number: " + i + " is " + - String.valueOf(entry[i])); + logger.debug("Entry number: " + i + " is " + + String.valueOf(entry[i])); </div> - <p> - incurs the cost of constructing the message parameter, that - is converting both integer - <code>i</code> - and - <code>entry[i]</code> - to a String, and concatenating intermediate strings. This, - regardless of whether the message will be logged or not. + <p> incurs the cost of constructing the message parameter, that is + converting both integer <code>i</code> and <code>entry[i]</code> + to a String, and concatenating intermediate strings. This, + regardless of whether the message will be logged or not. </p> <p> - One possible way to avoid the cost of parameter construction - is by surrounding the log statement with a test. Here is an + One possible way to avoid the cost of parameter construction is + by surrounding the log statement with a test. Here is an example. </p> <div class="source"> - if(logger.isDebugEnabled()) { - <br /> - logger.debug("Entry number: " + i + " is " + - String.valueOf(entry[i])); - <br /> - } - </div> +if(logger.isDebugEnabled()) { + logger.debug("Entry number: " + i + " is " + + String.valueOf(entry[i])); +} </div> - <p> - This way you will not incur the cost of parameter - construction if debugging is disabled for - <code>logger</code> - . On the other hand, if the logger is enabled for the DEBUG - level, you will incur the cost of evaluating whether the - logger is enabled or not, twice: once in - <code>debugEnabled</code> - and once in - <code>debug</code> - . This is an insignificant overhead because evaluating a - logger takes less than 1% of the time it takes to actually - log a statement. + <p> This way you will not incur the cost of parameter construction + if debugging is disabled for <code>logger</code> . On the other + hand, if the logger is enabled for the DEBUG level, you will incur + the cost of evaluating whether the logger is enabled or not, + twice: once in <code>debugEnabled</code> and once in + <code>debug</code> . This is an insignificant overhead because + evaluating a logger takes less than 1% of the time it takes to + actually log a statement. </p> <h4>Better alternative based on format messages</h4>